METAL OXIDE NANOFIBROUS MATERIALS FOR PHOTODEGRADATION OF ENVIRONMENTAL TOXINS

Abstract

Mixed-phase TiO.sub.2 nanofibers prepared via a sol-gel technique followed by electrospinning and calcination are provided as photocatalysts. The calcination temperature is adjusted to control the rutile phase fraction in TiO.sub.2 nanofibers relative to the anatase phase. Post-calcined TiO.sub.2 nanofibers composed of 38 wt % rutile and 62 wt % anatase exhibited the highest initial rate constant of UV photocatalysis. This can be attributed to the combined influences of the fibers' specific surface areas and their phase compositions.

Claims

1. A method of forming a photocatalyst fiber, comprising: forming a polymeric syspension of titanium oxide sol-gel precursor; electrospinning the polymeric suspension to form a fibrous layer; and calcining the fibrous layer, to produce photocatalytic titanium oxide fibers, wherein the photocatalyst fiber is photoexcitable to produce electron-hole pairs with an ability to form reactive radical species of proximate molecules from both the conduction band and the valence band.

2. The method according to claim 1, wherein the photocatalytic titanium oxide fibers have a ratio of rutile to anatase of at least 3:97

3. The method according to claim 1, wherein the photocatalytic titanium oxide fibers further comprise at least one of a catalytic metal and graphene.

4. The method according to claim 1, wherein the photocatalytic titanium oxide fibers further comprise a metal-organic framework (MOF).

5. The method according to claim 1, wherein the photocatalytic titanium oxide fibers further comprise a Poly(3,4-ethylenedioxythiophene) (PEDOT) surface film.

6. The method according to claim 1, wherein the photocatalytic titanium oxide fibers further comprise a dye which interacts with light to at least one of: elevate an electron into a conduction band in the photocatalytic titanium oxide fibers; and produce a hole in a valence band electron in the photocatalytic titanium oxide fibers.

7. The method according to claim 1, wherein the photocatalytic titanium oxide fibers further comprise a dopant in the titanium oxide which induces semiconductivity.

8. The method according to claim 1, wherein the photocatalytic titanium oxide fibers a distinct rutile phase and an anatase phase, the rutile phase being adapted to absorb photons, form hydroxyl radicals and hydrogen anions from surface absorbed hydroxyl, and to transfer electrons to an anatase phase; and the anatase phase is adapted to absorb photons, form superoxide radicals from surface absorbed oxygen, and receive electrons from the rutile phase.

9. The method according to claim 1, wherein the fibrous layer is calcined under conditions that result in a crystalline substantially inorganic solid.

10. A photocatalytic method, comprising: providing nanofibers calcined from small molecule titanium oxide sol-gel precursors to form a crystalline material comprising titanium dioxide; photoexciting the nanofibers to form electron-hole pairs; forming free radicals from surface adsorbed molecules from both the conduction band and the valence band of the photoexcited nanofibers.

11. The method according to claim 10, wherein the nanofibers have a relative ratio of rutile to anatase of at least 3:97.

12. The method according to claim 10, wherein the free radicals comprise hydroxyl radicals and superoxide radicals, wherein the free radicals are formed in a solution containing an organic compound, to thereby degrade the organic compound.

13. The method according to claim 12, wherein the organic compound is provided in an aqueous effluent stream.

14. The method according to claim 10, wherein the nanofibers further comprise at least one of a catalytic metal, graphene, a metal-organic framework (MOF), a Poly(3,4-ethylenedioxythiophene) (PEDOT) surface film, and a dopant in the titanium oxide which induces semiconductivity.

15. The method according to claim 10, wherein the nanofibers fibers further comprise a dye which interacts with light to transfer an electron into a conduction band in the titanium dioxide.

16. The method according to claim 10, wherein the nanofibers further comprise a dye which interacts with light to at least one of: facilitate production of a hole in a valence band electron in the titanium dioxide. facilitate elevation of an electron to a conduction band in the titanium dioxide.

17. The method according to claim 10, wherein: the nanofibers comprise a rutile phase and an anatase phase; the rutile phase is adapted to absorb photons, form hydroxyl radicals and hydrogen anions from surface absorbed hydroxyl, and to transfer electrons to an anatase phase; and a the anatase phase is adapted to absorb photons, form superoxide radicals from surface absorbed oxygen, and receive electrons from the rutile phase.

18. A method of forming a photocatalyst, comprising: providing photocatalytic titanium oxide fibers formed by calcining an electrospum polymeric suspension of a titanium oxide sol-gel precursor, wherein the photocatalytic titanium oxide fibers comprise a distinct crystaline rutile phase and a distinct crystalline anatase phase, the rutile phase being adapted to absorb photons, form hydroxyl radicals and hydrogen anions from surface absorbed hydroxyl, and to transfer electrons to an anatase phase, and the anatase phase is adapted to absorb photons, form superoxide radicals from surface absorbed oxygen, and receive electrons from the rutile phase; moistening the photocatalytic titanium oxide fibers; irradiating the moistended photocatalytic titanium oxide fibers with UV or visible radiation; and degrading an organic compound with the irradiated, moistended photocatalytic titanium oxide fibers.

19. The method according to claim 18, wherein the photocatalytic titanium oxide fibers have a ratio of rutile to anatase of at least 3:97

20. The method according to claim 18, wherein the photocatalytic titanium oxide fibers further comprise at least one of a catalytic metal, graphene, a metal-organic framework (MOF), a Poly(3,4-ethylenedioxythiophene) (PEDOT) surface film, a dopant in the titanium oxide which induces semiconductivity, and a dye which interacts with light to at least one of: (i) elevate an electron into a conduction band in the photocatalytic titanium oxide fibers; and (ii) produce a hole in a valence band electron in the photocatalytic titanium oxide fibers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0102] These and other features and advantages of the present invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

[0103] FIG. 1 shows a schematic figure showing three typical processes of fabricating TiO.sub.2 nanofibers including sol-gel method, electrospinning technique and calcination treatment.

[0104] FIG. 2 shows scanning Electron Microscopy images of (a) pre-calcined polymer nanofibers; post-calcined TiO.sub.2 nanofibers at (b) 285 C., (c) 320 C., (d) 360 C., (e) 400 C., (f) 600 C. for 4 hours under ambient atmosphere.

[0105] FIG. 3 shows X-ray diffraction patterns of post-calcined TiO.sub.2 nanofibers after 285 C., 320 C., 360 C., 400 C. & 600 C. calcinations for 4 hours under ambient atmosphere, where the A and R in the figure denote the anatase and rutile phases of TiO.sub.2, respectively.

[0106] FIG. 4 shows PAP concentration changes based on liquid UV-Vis spectroscopy on aliquots picked up at T=60, 30, 0, 10, 20, 30, 45, 60 using TiO.sub.2 nanofibers with different rutile fractions.

[0107] FIG. 5 shows first 30-min initial rate constants for photodegradations under UV irradiation using post-calcined TiO.sub.2 nanofibers after 285 C., 320 C., 360 C., 400 C., 600 C. calcination for 4 hours under ambient atmosphere.

[0108] FIG. 6 shows specific surface area measurement of five TiO.sub.2 nanofibers with different rutile fraction using Brunauer-Emmett-Teller (BET) method plotted with their initial rate constants during the degradation process as a function of calcination temperature.

[0109] FIG. 7 shows a proposed schematic representation of possible electron-hole separation pathway mechanism for anatase and rutile mixed-phase TiO2 nanofibers during the photocatalysis process of PAP.

[0110] FIG. 8 shows a schematic image of the photodegradation process on the surface of TiO.sub.2.

[0111] FIGS. 9A, 9B and 9C show an EDS spectrum of 5 wt % PtTiO.sub.2, showing elemental composition and distribution; a TEM image of TiO.sub.2 nanofiber surface decorated with 4 nm Pt nanoparticles, and an SEM image of TiO.sub.2 nanofibers showing the presence of numerous pores on the titania surface.

[0112] FIG. 10 shows a phenazopyridine structure and UV-Vis absorption spectrum showing the progress of phenazopyridine photodegradation with reaction time.

[0113] FIG. 11 shows Rhodamine B structure and UV-Vis absorption spectrum showing the progress of Rhodamine B. photodegradation with reaction time.

[0114] FIG. 12 shows a schematic representation of the electrospinning process.

[0115] FIG. 13 shows an X-ray diffraction profile of TiO.sub.2 nanofibers under different temperature calcination for 4 hrs in air.

[0116] FIG. 14 shows PMMA/TIP polymer fibers with different diameters under calcination at 359 C. for 4 hrs in air.

[0117] FIG. 15 shows a scanning electron microscopy image of calcined TiO.sub.2 nanofibers with diameters of 192.410.42 nm.

[0118] FIG. 16 shows a UV-Vis spectra of PAP solution at T=60, 0, 75, 120, 180 minutes.

[0119] FIG. 17 shows nuclear magnetic resonance of photocatalysis of 100 M solution of DMMP with P25 nanoparticles in a quartz vial.

[0120] FIG. 18 shows nuclear magnetic resonance of photocatalysis of 100 M solution of DMMP with anatase TiO.sub.2 nanofibers in a quartz vial.

[0121] FIG. 19 shows the relationship between time and Rh.B concentration percentage.

[0122] FIGS. 20A, 20B and 20C show, an SEM image of N3-dye sensitized TiO.sub.2 nanofibers (FIG. 20A); a TEM image of N3-dye sensitized TiO.sub.2 nanofibers (FIG. 20B); and EDX mapping image of N3-dye sensitized TiO.sub.2 nanofibers with purple spots of Ru.sup.2+ (FIG. 20C).

[0123] FIG. 21 shows UV-Vis spectra of PAP solution at T=45, 30, 15, 0, 15, 30, 45 and 60 minutes.

[0124] FIG. 22 shows scanning electron microscopy image of platinum nanoparticles supported on electrospun TiO.sub.2 nanofibers.

[0125] FIG. 23 shows Anatase TiO.sub.2 nanofibers, diameter 30050 nm.

[0126] FIG. 24 shows .sup.13C NMR-Photocatalysis of 2CEES in a nucleophilic solvent with anatase TiO.sub.2 nanofibers.

[0127] FIG. 25 shows .sup.13C NMR-Photocatalysis of 2CEES in an acetone/water solution with anatase TiO.sub.2 nanofibers.

[0128] FIG. 26 shows photocatalysis of 2CEES in the presence of anatase TiO.sub.2 nanofibers without solvent and irradiation in a quartz vial.

[0129] FIG. 27 shows photocatalysis of 2CEES in the presence of anatase TiO.sub.2 nanofibers without solvent and with irradiation in a quartz vial.

[0130] FIG. 28 shows photocatalysis of 2CEES in the presence of water saturated anatase TiO2 nanofibers without solvent and irradiation in a quartz vial.

[0131] FIG. 29 shows photocatalysis of 2CEES in the presence of water saturated anatase TiO2 nanofibers without solvent and irradiation in a quartz vial.

[0132] FIG. 30 shows .sup.13C NMR-Photocatalysis of 2CEES with water saturated TiO.sub.2 nanofibers over 24 hours of UV Irradiation.

[0133] FIG. 31 shows .sup.13C NMR-Photocatalysis of 2CEES with water saturated silica gel over 24 hours of UV Irradiation.

[0134] FIG. 32 shows UV-Vis of photocatalysis product after 24 hours of UV irradiation with silica gel.

[0135] FIG. 33 shows .sup.13C NMR-Hydrolysis study of Dimethylmethyl phosphonate over 72 hours.

[0136] FIG. 34 shows .sup.13C NMR-Photocatalysis of DMMP with standard Degussa P25 nanoparticles in DI water over 8 hours of UV irradiation.

[0137] FIG. 35 shows .sup.31P NMR-Photocatalysis of DMMP with anatase TiO.sub.2 nanofibers in water over 4 hours of UV irradiation.

[0138] FIG. 36 shows photocatalysis of 100 M solution dimethyl methylphosphonate with anatase TiO.sub.2 nanofibers in a 100 mL quartz beaker over 2 hours of UV irradiation.

[0139] FIG. 37 shows photocatalysis of 100 M solution dimethyl methylphosphonate with anatase TiO.sub.2 nanofibers in a 16 mL quartz vial over 2 hours of UV irradiation.

[0140] FIG. 38 shows TEM imaging of Pt nanoparticles supported on the surface of anatase TiO.sub.2 nanofibers.

[0141] FIG. 39 shows .sup.31P NMR of Photocatalysis with 100 M solution of dimethyl methylphosphonate and Pt nanoparticles supported on anatase TiO.sub.2 nanofibers for 4 hours of UV irradiation.

[0142] FIG. 40 shows SEM (above) and TEM (bottom) images of 2 varying diameters of anatase TiO.sub.2 nanofibers ranging from 200 to 300 nm in diameter.

[0143] FIG. 41A shows the molecular formula of N3.

[0144] FIGS. 41B and 41C show UV-VIS spectra of N3 solution and UV-VIS of photodegradation of Phenazopyridine (PAP) using N3-sensitized TiO.sub.2 nanofiber (from left to right), respectively.

[0145] FIG. 41D shows a Relative wide band gap of TiO.sub.2, which limits its application as photocatalyst using under visible light; N3-dye can absorb visible light and get excited to generate free electrons and transfer to TiO.sub.2, which enlarge the application of TiO.sub.2-based photocatalyst.

[0146] FIG. 42 shows photocatalysis of 100 M solution of dimethyl methylphosphonate with Degussa P25 TiO.sub.2 nanoparticles over 4 hours of UV irradiation.

[0147] FIG. 43 shows photocatalysis of 100 M solution of dimethyl methylphosphonate with anatase TiO.sub.2 nanofibers over 2 hours of UV irradiation.

[0148] FIG. 44 shows Raman spectra of anatase TiO.sub.2 nanofibers before and after photocatalysis with DMMP.

[0149] FIG. 45 shows an SEM image of blended PMMA/PMMA:TIP polymer fibers.

[0150] FIG. 46 shows EDX (mapping) polymer blended nanofibers where blue represents titanium distributed in the matrix.

[0151] FIG. 47 shows EDX (mapping) polymer blended nanofibers where green represents oxygen distributed in the matrix.

[0152] FIG. 48 shows EDX (mapping) polymer blended nanofibers where red represents the carbon distributed in the matrix.

[0153] FIG. 49 shows .sup.31P NMR of the photodegradation of 100 M DMMP with TiO.sub.2 nanofibers.

[0154] FIGS. 50A and 50B show that the degradation process is a first-order reaction; Anatase/RGO has a higher initial rate constant (k=0.0384 min.sup.1) than pure anatase nanoparticles (k=0.0301 min.sup.1) during the first 30 mins degradation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0155] Certain exemplary embodiments of the present invention will now be described in greater detail with reference to the accompanying drawings.

[0156] TiO.sub.2 nanofibers were prepared with different rutile fractions ranging from 3 wt % to 97 wt % by adjusting their calcination temperature.

[0157] These materials were applied to the photocatalytic degradation of a model pharmaceutical agent, phenazopyridine [2,6-diamino-3-(phenylazo)pyridine hydrochloride, (PAP)], which is used commercially as an analgesic for urinary tract infections [37,38]. Physical characterization combined with determination of initial degradation rate constants provided insight to the mechanism and optimization of these new materials for decontaminating toxic pharmaceutical agents in water.

##STR00001##

Example 1

[0158] Polymethylmethacrylate (PMMA) (M.sub.w 960,000), titanium isopropoxide (TTIP), N,N-dimethylformamide (DMF), chloroform and phenazopyridine hydrochloride (PAP) (M.sub.w 249.70) were all acquired from Sigma Aldrich and used as received.

[0159] 1 2 mL of PAP solution with concentration of 144 M was prepared using DI water as solvent. The solution was transferred into a 16 mL cylindrical quartz container and placed in a fume hood with the lights off. After blanking the UV-Vis Spectrophotometer with DI water in a small quartz cell, an initial reading (marked as T=60) was taken by diluting 0.5 mL of the PAP solution with 2.0 mL of DI water. Next, 12.0 mg of the catalyst TiO.sub.2 nanofibers were added into the 12 mL PAP solution with constant stirring. After 30 and 60 minutes stirring, a 1.0 mL aliquot of the sample was taken and centrifuged for two minutes, which are recoded as sample T=30 and T=0. Once the sample of T=0 was taken, a UV lamp was turned on at a fixed distance of 9 cm from the center of the quartz cell and 1.0 mL aliquot of the sample was took every 10 minutes and centrifuged for two minutes. Once the centrifuging was complete, 0.5 mL of the upper solution from th

[0160] e mixture was taken off from the top of the sample and diluted with 2 mL of DI water. The diluted sample was run through the UV-Vis Spectrophotometer and an absorbance spectrum was obtained at T=10, 20, 30, 45, 60.

[0161] The electrospun pre-calcined polymer fibers were fabricated using a high voltage Spellman SL 30 generator, where a high electrical potential was applied across the syringe needle attached to a copper wire and the collector screen. The photodegradation experiments were performed using an Oriel 66001 UV lamp with Oriel 68805 40-200 Watt universal Arc lamp power supply, which covered all the UV ranges. The distance between the center of the solution container and the UV lamp was controlled at 9 cm. UV-Visible analysis of the aliquots was performed on an 8452A Hewlett Packard Diode Array spectrophotometer instrument with wavelength from 190 nm to 820 nm to characterize the absorption spectra of the aliquots to determine the phenazopyridine concentration changes and also to identify the degradation products. Sample analyses were performed in distilled water unless otherwise noted. The morphological and structural characteristics of the pre-calcined polymer and after-calcined TiO.sub.2 nanofibers were measured by field emission scanning electron microscopy (FESEM, Supra 55 VP from Zeiss equipped with an EDAX energy dispersive X-ray spectroscopy detector), and X-ray diffraction (XRD, PANalytical's X'Pert PRO Materials Research Diffractometer with Cu K radiation (=1.5418 )) respectively. Specific surface area of the samples was measured by Brunauer-Emmett-Teller (BET) method using a surface analyzer.

[0162] TiO.sub.2 nanofibers were prepared by a typical sol-gel synthesis followed by electrospinning technique and calcination treatment shown in the schematic FIG. 1. A polymeric sol-gel was generated by stirring and hydrolysis of TTIP using 1:2 mass ratio of PMMA:TTIP, where 320 mg of PMMA was dissolved in 2 mL chloroform followed by drop wise addition of 640 mg of TTIP with continuous stirring. 2 mL DMF was then added to increase the dielectric constant of the composite solution required for the electrospinning. The high voltage would pull the precursor sol-gel from the syringe onto the conductive collector forming polymer nanofibers. The resulting polymer fibers were left overnight to allow for complete hydrolysis of TTIP to TiO.sub.2 followed by heat calcination for transformation from amorphous phase to crystal phases. By adjusting the calcination temperatures from 285 C. to 600 C., TiO.sub.2 nanofibers with different composition fractions of anatase phase and rutile phase can be fabricated under ambient atmosphere for 4 hours.

[0163] FIG. 2 presents six SEM images of pre-calcined polymer fibers and the post-calcined TiO.sub.2 fibers followed by calcination after 285 C., 320 C., 360 C., 400 C. and 600 C. for 4 hours under ambient atmosphere. As shown, TiO.sub.2 nanofibers after calcination at 285 C., 320 C., 360 C. and 400 C. all had folded surface morphology. And their average diameters didn't change much compared with the pre-calcined polymer fibers shown in table 1. When the temperature increased to 600 C., the morphology of the fibers was obviously different and the diameter shrank a lot. It also showed much smoother surface with a larger grain size from the surface observation.

TABLE-US-00001 TABLE 1 Samples prepared under different temperature calcination showing different diameters, rutile fractions and grain sizes. Anatase Rutile Sample Calcination Rutile Phase Phase in SEM temperature Diameter Fraction Grain Grain Size image ( C.) (nm) (%) Size (nm) (nm) A N/A 761.6 40.3 N/A N/A N/A B 285 666.0 43.8 8 16.77 33.68 C 320 720.5 40.3 16 11.18 15.55 D 360 676.5 60.0 38 13.41 22.45 E 400 685.3 42.4 67 16.77 25.26 F 600 441.2 41.4 97 50.25 33.68

[0164] The XRD patterns of post-calcined TiO.sub.2 nanofibers at 285 C., 320 C., 360 C., 400 C. and 600 C. with 4 hours holding times under ambient atmosphere are shown in FIG. 3. The A and R in the figure denoted the anatase and rutile phases, respectively. Well defined diffraction peaks for the post-calcined TiO.sub.2 nanofibers suggested the presence of both anatase and rutile phases. For anatase phase, the major peaks were obtained at 2 theta values of 25.5, 37.9, 48.2, 53.8, and 55.0 representing the Miller indices of (101), (004), (200), (105), and (211) planes, while for rutile peaks were observed at 27.6, 36.1, 41.2, and 54.3, which correspond to the Miller indices of (110), (101), (111), and (211) planes. It was clearly seen that with increasing calcination temperature, the intensities ratio between the rutile phase and the anatase phase increased simultaneously. The weight fraction of anatase-to-rutile transformation in the post-calcined TiO.sub.2 nanofibers can be calculated from the equation W.sub.R=1/[1+0.8(I.sub.A/I.sub.R)] [19,26,27], where I.sub.A is the X-ray integrated intensities of the (101) reflection of anatase around 25.5 and I.sub.R is that of the (110) reflection of rutile around 27.6. The fraction of rutile phase in TiO.sub.2 nanofibers was found to increase with increasing calcination temperature from 8% to 97% shown in table 1. Almost pure rutile nanofibers can be prepared around 600 C. calcination for 4 hours under ambient atmosphere.

[0165] According to Scherrer Equation based on XRD pattern in FIG. 3, the grain sizes of anatase and rutile phase can be calculated and are listed in Table 1. When calcination temperature increased, the size of anatase and rutile grains increased as well as the rutile fractions. It suggested that the transformation from anatase to rutile phase and the grains growth happened at the same time.

[0166] In order to study the influence of rutile fraction in TiO.sub.2 nanofiber on the photodegradation activities, six degradation experiments with and without using nanofibers with different rutile fractions were performed under the same condition. 144 M of PAP solution was used as the initial pollutant for photodegradation. Based on the UV-Vis absorbance peak changes at 428 nm, the PAP concentration changes both in the dark and under UV irradiation were plotted as a function of time shown in FIG. 4. Pure PAP solution without any catalysts was very stable regardless of whether it is maintained in the dark or subjected to UV irradiation. As the weight fraction of rutile phase increased from 8% to 38%, the photodegradation activity of the TiO.sub.2 nanofibers improved. However, further increase of the rutile fraction led to a slower degradation activity. All PAP solution could be completely degraded in 45 minutes by using the TiO.sub.2 nanofibers with 38 wt % of rutile.

[0167] FIG. 5 shows first 30-min initial rate constants for photodegradations under UV irradiation using post-calcined TiO.sub.2 nanofibers after 285 C., 320 C., 360 C., 400 C., 600 C. calcination for 4 hours under ambient atmosphere.

[0168] Based on FIG. 4, the data were best fit under pseudo-first-order reaction. The rate constant and the kinetic equation can be expressed as C=C.sub.0e.sup.kt, where t is the reaction time; k is the rate constant; C.sub.0 and C are the PAP initial concentration and concentration at reaction time of t, respectively. The initial rate constant k during the first 30-min degradation period using five TiO.sub.2 nanofibers with different rutile fractions were calculated and plotted with the rutile fractions together as a function of calcination temperature shown in FIG. 5. It was clear that the initial rate constant of TiO.sub.2 nanofibers strongly depends on the rutile fraction in the nanofibers, which could be tuned through the calcination temperature. The optimal initial rate constant was 0.044 min.sup.1 using TiO.sub.2 nanofibers with 38 wt % of rutile after calcination at 360 C. for 4 hours under ambient atmosphere.

[0169] FIG. 6 shows specific surface area measurement of five TiO.sub.2 nanofibers with different rutile fraction using Brunauer-Emmett-Teller (BET) method plotted with their initial rate constants during the degradation process as a function of calcination temperature.

[0170] TiO.sub.2 nanofibers with 38 wt % of rutile phase exhibited the best initial rate constant during the PAP degradation process. Specific surface area of the five TiO.sub.2 nanofibers was measured by Brunauer-Emmett-Teller (BET) method. The result showed us that, as the rutile fraction increased, the surface area of the TiO.sub.2 nanofibers decreased, which suggested that the TiO.sub.2 nanofibers with higher fraction of rutile phase had a lower surface area. If other factors are not considered, higher surface area would leave more active sites for H.sub.2O and O.sub.2 adsorbed on the surface for the generation of more active radicals to get a better degradation initial rate constant. TiO.sub.2 nanofibers with higher surface area have a better initial rate constant. FIG. 6 shows that the TiO.sub.2 nanofibers with 38 wt % of rutile and surface area of 22 m.sup.2/g had the best initial rate constant of 0.044 min.sup.1 rather than 8 wt % rutile nanofibers with higher surface area of 108 m.sup.2/g got the best initial rate constant. Therefore, it appears that surface area is not the only factor determining the photoactivity efficiency.

[0171] FIG. 7 shows a proposed schematic representation of possible electron-hole separation pathway mechanism for anatase and rutile mixed-phase TiO.sub.2 nanofibers during the photocatalysis process of PAP.

[0172] Rutile fraction difference is believed to be another factor leading to the different initial rate constants. During the calcination process, amorphous phase TiO.sub.2 was firstly going to transfer to anatase phase at a relative lower temperature. As the calcination kept going, small anatase crystal would like to grow to a bigger one. The photocatalytic activity principle of anatase and rutile mix-phase TiO.sub.2 nanofibers is hypothesized as shown in FIG. 7. Recently a new understanding of the band alignment between rutile and anatase showed that the electron affinity of anatase was higher than rutile and the conduction electrons would flow from rutile to anatase [39], which helped to explain the electron-hole separation during the photodegradation process of PAP. As shown in FIG. 7, between anatase and rutile phases, the photoexcited electrons would migrate from conduction band of rutile to conduction band of anatase. Meanwhile, the electrons in the valence band of rutile also tended to migrate into valence band of anatase. This electron transfer process could also be regarded as the holes transportation from anatase to rutile. This whole process made the excited electron-hole pairs exist separately in the conduction band of anatase and valence band of rutile. This would effectively increase the charge separation, decrease the electron-hole pair recombination and consequently improve the photocatalytic efficiency of the post-calcined TiO.sub.2 nanofibers. The electrons and holes were going to separately react with surface adsorbed H.sub.2O and O.sub.2 to generate active hydroxyl radicals and superoxide radical anions. These oxidizing radicals would consequently react with PAP and decompose it into some other smaller molecules. During this process, oxygen-hydrogen bond in H.sub.2O was going to break and electrons would migrate into valence band of rutile to replenish the excited missing electrons making the nanofibers reusable.

[0173] As the calcination temperature increased, more rutile phase showed up in the post-calcined TiO.sub.2 nanofibers. This change made the surface area of post-calcined TiO.sub.2 nanofibers decrease. Theoretically, the initial rate constant would decrease as a result of decreased specific surface area. However, more rutile phase in the post-calcined TiO.sub.2 nanofibers would help to improve the electron-hole pair separation to increase the initial rate constant. These two factors competed with each other making the 38 wt % of rutile fraction TiO.sub.2 nanofibers have the best initial rate constant.

[0174] TiO.sub.2 nanofibers with different rutile fractions ranging from 3 wt % to 97 wt % were successfully synthesized by sol-gel method followed by electrospinning and calcination at different temperatures under ambient atmosphere. As the calcination temperature increased, the rutile fraction in TiO.sub.2 nanofibers increased as well, however the surface area showed an opposite trend. The photocatalytic activity showed that post-calcined TiO.sub.2 nanofiber calcined at 360 C. containing 38 wt % of rutile got the highest initial rate constant and the fastest degradation efficiency. 144 M PAP could be completely removed in 45 mins The existence of an optimum rutile fraction in TiO.sub.2 nanofiber can be explained by the competition between less surface area decreasing the generation of radicals and appropriate amount of rutile phase leading to more efficient electron-hole separation and more generation of radicals. 38 wt % rutile TiO.sub.2 nanofibers provided a new type of material for the future application in the pharmaceutical waste treatment and other environmental remediation.

Example 2

[0175] Nanotechnology can provide new approaches to the real time decontamination of liquids and solid surfaces. For example, photocatalytic and self-cleaning ability on the hydrophilic surface of TiO.sub.2 have found multiple uses in health, environmental and military applications. Specifically, TiO.sub.2-based electrospun fibers have great potential for use in chemical and biological decomposition [44], protective/self-cleaning clothing [40,45], self-cleaning glass [46], and self-cleaning membranes. [47] The basic principle of photocatalytic activity is the use of incident light to excite an electron from the valence band (leaving behind a hole) to the conduction band of a semiconductor. These photoinduced charge carriers then proceed to form reactive radicals, hydroxyl radicals (A) and super oxide radicals (D+) that attack adsorbed chemicals on the surface of the material, as shown in FIG. 8, which shows a schematic image of the photodegradation process on the surface of TiO.sub.2. Previous research on titania modified textiles has concentrated on increasing the number of hydroxyl and carboxyl radicals on the surface of the fiber. [48-49].

[0176] Major setbacks in this area of research are the low surface-volume ratios, limiting adsorption capability and photocatalytic activity, and the use of UV light for photo-excitation, which prevents the use of low intensity of typical indoor working conditions. Our objective is to use the electrospinning technique to fabricate TiO.sub.2 fibers with large surface area for heterogeneous catalysis. [50,51]

[0177] FIGS. 9A-9C shows FIG. 9A: EDS spectrum of 5 wt % PtTiO.sub.2, showing elemental composition and distribution. FIG. 9B: TEM image of TiO.sub.2 nanofiber surface decorated with 4 nm Pt nanoparticles. FIG. 9C: SEM image of TiO.sub.2 nanofibers showing the presence of numerous pores on the titania surface.

[0178] FIG. 10 shows a UV-Vis absorption spectrum showing the progress of phenazopyridine photodegradation with reaction time.

[0179] In addition to metal nanoparticles supported on TiO.sub.2 nanoparticles, high surface area graphene nanoparticles may be incorporated into the TiO.sub.2 anatase crystallites for increased absorption and diffusion of reactants within the TiO.sub.2 surface. Graphene's increased electron conductivity is expected to modify TiO.sub.2's electronic, crystal and surface structures to allow the application of low intensity room lighting for the decontamination of organic pollutants. Preliminary studies have shown successful degradation of phenazopyridine, a pharmaceutical drug, using low intensity room lighting.

[0180] FIG. 11 shows Rhodamine B Structure, and UV-Vis absorption spectrum showing the progress of Rhodamine B. photodegradation with reaction time. Further investigation into the varying forms of carbon such as amorphous carbon can potentially be said to have an improvement on decontamination of organic pollutants. The presence of amorphous carbon in and throughout the surface of titania will not only increase the surface area but expand the pore size allowing for functionalization. Initial studies have shown promising initial rates of degradation of Rhodamine B. in ultra-violet irradiation. Using the polyol synthesis to deposit noble metals [51] on the surface of TiO.sub.2-AC (Amorphous Carbon) metals such as platinum can be used as an anchor for metal organic frameworks for degradation. If successful, the technology and materials developed in this work have the potential to be utilized in environmental decontamination from chemical and biological contaminants, tissue engineering, drug delivery and clothing/textile self-cleaning applications.

[0181] Huge amounts of environmental toxins, such as toxic industrial chemicals (TICs), toxic organic dyes, bio-pharmaceuticals, and chemical warfare agents (CWAs), bio-accumulate causing chronic and aesthetic pollution to the surrounding environments and human beings. Systems must therefore be put in place for treatment methods that ensure complete degradation (with no secondary pollution) before being released into the environment. Compared with other photocatalytic materials, one-dimensional metal oxide nanofibrous materials have attracted considerable attention due to their high specific surface area, ease of fabrication and functionalization, and versatility in controlling the fiber diameter and morphology. Electrospun nanofibers from stable polymers are ideal candidates for catalytic supports as they can provide a large surface area and a high porosity for catalytic applications. In order to develop novel self-cleaning surfaces and substrates for photodegradation of environmental toxins, some fundamental studies have been investigated on the electrospinning technique, calcination temperature influence on TiO.sub.2 phase changes and phase transformation rates of pre-calcined polymer fibers with different diameters. We have prepared a variety of electrospun nanofibrous materials such as, anatase TiO.sub.2, rutile TiO.sub.2, reduced graphene oxide TiO.sub.2, BaTiO.sub.3, platinum nanoparticles supported on anatase TiO.sub.2, ZnO, photoactive dye supported anatase TiO.sub.2. These fibers have been characterized by X-Ray diffraction, Scanning Electron Microscopy, Transmittance Electron Microscopy, Raman Microscopy and Energy-Dispersive X-Ray Spectroscopy. Also, electrospun TiO.sub.2 nanofibers show excellent UV degradation results on Rhodamine B (Rh.B.), phenazopyridine (PAP) and dimethyl methylphosphonate (DMMP). The photocatalytic activity of pure TiO.sub.2 fibers is limited by fast electron-hole pairs' recombination and a relative high energy band gap. Some multifunctional TiO.sub.2 fibers have been also fabricated to solve these problems. These novel multifunctional materials offer excellent mobility of charge carriers for faster degradation and the possibility to exploit catalytic processes in decontamination.

[0182] For synthesis procedure, sol-gel method is used to get the pre-electrospinning solution. A 1:2 weight ratio of polymethylmethacrylate (PMMA): titanium isopropoxide (TIP) was prepared by completely dissolving PMMA in chloroform followed by drop wise addition of TIP with continuous stirring of the reaction mixture for complete dissolution. Small amount of dimethylformamide (DMF) was added to increase the dielectric constant of the composite solution and hence enable the electrospinning process at a high voltage. The hydrophobic nature of both PMMA and TIP enabled the formation of a homogeneous solution of the polymer blend. Electrospinning is a non-mechanical, electrostatic process that produces fibers in the nanometer to micrometer range using electrically driven jets of polymer solution. 15-40 kV was applied across the syringe needle and the collector screen where the PMMA/TIP solution was spun into composite nanofibers and deposited as a randomly oriented non-woven mat on the collector screen. These polymer fibers were left overnight to undergo hydrolysis reactions, followed by thermal treatment in order to favor structural stability via sintering, densification, grain growth and phase transformation.

Example 3

[0183] FIG. 12 shows a schematic representation of the electrospinning process Calcination temperature influence on TiO.sub.2 phase changes. Based on the calcination temperatures, TiO.sub.2 nanofibers show different phase combination, pure anatase, pure rutile or their mixture. The X-ray diffraction (XRD) in FIG. 13 clearly shows that pure anatase phase of TiO.sub.2 shows up at relative lower temperature and it begins to transfer to rutile phase as the temperature increases. The ratios of anatase phase and rutile phase under different temperature are shown in table 1.

TABLE-US-00002 TABLE 2 Polymer nanofibers with different diameters prepared under different electrospinning parameters Distance PMMA/TIP PMMA between Tip Polymer Diameter PMMA:TTIP Molecular to Collector Voltage Fiber (nm) (mg) Weight (cm) (kV) Humidity A 638.4 26.3 320:640 996,000 18 25 43% B 761.6 40.3 320:640 996,000 11 25 85% C 972.8 134.8 320:640 996,000 11 25 43%

[0184] PMMA/TIP polymer fibers with different diameters can be fabricated by altering the parameters used in sol-gel preparation and electrospinning process as shown below in Table 2. As shown in Table 2, humidity is and tip distance both influence fiber diameter.

[0185] FIG. 13 shows X-ray diffraction profile of TiO.sub.2 nanofibers under different temperature calcination for 4 hrs in air.

[0186] As shown in FIG. 14, under the same calcination condition polymer fibers with larger diameters have a faster anatase to rutile transformation rates and larger grain sizes.

TABLE-US-00003 TABLE 3 Calcination temperature vs. anatase/Rutile phase fraction Calcination Temperature Anatase Phase Rutile Phase ( C.) Fraction (%) Fraction (%) 325 100 0 400 85 15 465 74 26 580 61 39 600 0 100

[0187] Table 3 shows the phase fraction of anatase and rutile in TiO.sub.2 nanofibers under different temperature calcination.

[0188] FIG. 14 shows PMMA/TIP polymer fibers with different diameters under calcination at 359 C. for 4 hrs in air Photodegradation of PAP using electrospun TiO.sub.2 nanofibers under UV light. TiO.sub.2 nanofibers with diameter of 192.410.42 nm were fabricated and utilized as the photocatalyst in degradation of PAP solution, as shown in the scanning electron microscopy image in FIG. 15. Firstly, stir PAP solution with catalyst in the dark for 60 mins to ensure adsorption/desorption equilibrium, extract 0.5 ml upper solution and dilute in 3 ml DI water to run UV-Vis analysis (T=60, 0). Then turn on UV lamp, continue stirring the solution and pick up mixture solution, centrifuge, extract upper solution and dilute after 75 mins, 120 mins and 180 mins irradiations. FIG. 16 shows a UV-Vis spectra of PAP solution at T=60, 0, 75, 120, 180 minutes. Photodegradation of DMMP using electrospun TiO.sub.2 nanofibers under UV light. From UV-Vis spectra in FIG. 16, it can be concluded that the concentration of PAP solution start to decrease after turning on the light. After 120 mins irradiation, almost all the PAP are degraded. At T=180 mins, new product peak is generated.

[0189] FIG. 17 shows nuclear magnetic resonance of photocatalysis of 100 M solution of DMMP with P25 nanoparticles in a quartz vial. FIG. 18 shows nuclear magnetic resonance of photocatalysis of 100 M solution of DMMP with anatase TiO.sub.2 nanofibers in a quartz vial. The multifunctional TiO.sub.2 fibers-TiO.sub.2/Reduced Graphene Oxide (RGO) Nanofibers result in photodegradation of Rh.B under visible light. As shown below in FIGS. 17 and 18, the degradation of DMMP using TiO.sub.2 nanofibers is much faster than using P25 nanoparticles that the DMMP peak disappears in 2 hrs using TiO.sub.2 nanofibers while it took 4 hrs using P25 nanoparticles.

[0190] FIG. 19 shows that TiO.sub.2/RGO nanofibers have a faster degradation rate than any other catalyst for photodegradation of Rh.B. under visible light. The best mass ratio between TiO.sub.2 and RGO is still under study.

[0191] FIG. 20 shows, Left to right: SEM image of N3-dye sensitized TiO.sub.2 nanofibers; TEM image of N3-dye sensitized TiO.sub.2 nanofibers; EDX mapping image of N3-dye sensitized TiO.sub.2 nanofibers with purple spots of Ru.sup.2+. As seen in SEM image in FIG. 20, N3 dyes are attached on the surface of TiO.sub.2 nanofibers. After soaking TiO.sub.2 and N3 dye together in NaOH solution, the N3 dye was able to bond to the TiO.sub.2 nanofibers. N3-sensitized TiO.sub.2 nanofibers were confirmed by using SEM, TEM and EDX mapping techniques.

[0192] FIG. 21 shows UV-Vis spectra of PAP solution at T=45, 30, 15, 0, 15, 30, 45 and 60 Novel multifunctional TiO.sub.2 fibersplatinum nanoparticles supported on electrospun TiO.sub.2 nanofibers. In FIG. 21, it shows that there is no PAP solution UV-Vis absorbance change when stirring in dark. After turning on the lamp, PAP absorbance peak starts to decrease, which shows the degradation process happens. FIG. 22 shows a scanning electron microscopy image of platinum nanoparticles supported on electrospun TiO.sub.2 nanofibers. Platinum nanoparticles supported on electrospun TiO.sub.2 nanofibers have faster electron-hole pairs separation and an improved degradation efficiency as compared to electrospun TiO.sub.2 nanofibers.

TABLE-US-00004 TABLE 6 Potential Target Pollutants. Simulated Toxic Industrial Chemical Warfare Chemicals (TICS) Abbreviation Agents (SCWAs) Abbreviation Ammonia NH.sub.3 2-Chloro ethyl CEES ethyl sulfide Arsine AsH.sub.3 Dimethyl DMMP methylphosphonate Boron trifluoride BF.sub.3 Dimethyl DMCP chlorophosphate Carbon disulfide CS.sub.2 Diisopropyl DIFP fluorophosphates Formaldehyde CH.sub.2O O,O-Dimethyl Methyl O-(4-nitrophenyl) Paraoxon phosphate Hydrogen cyanide HCN Hydrogen sulfide H.sub.2S Phosgene COCl.sub.2 Sulfur dioxide SO.sub.2 Carbon monoxide CO Methyl bromide CH.sub.3Br Nitrogen dioxide NO.sub.2 Phosphine PH.sub.3 Cyanogen chloride ClCN

[0193] The following types of agents may be degraded by the catalytic fiber:

[0194] Toxic organic dyes: Rhodamine B, Methyl Yellow, Methyl Red, etc.

[0195] Bio-pharmaceuticals: Phenazopyridine, etc.

[0196] Chemical warfare agents (CWAs): O-Pinacolyl methyl phosphonofluoridate (GD), (RS)-Propan-2-yl methylphosphonofluoridate (GB), (RS)-Ethyl N,N-Dimethylphosphoramidocyanidate (GA), Ethyl ({2-[bis(propan-2-yl)amino]ethyl}sulfanyl)(methyl)phosphinate (VX), bis(2-chloroethyl) sulfide (HD), 2-Chloroethyl Ethyl Sulfide, etc.

[0197] The photocatalytic fibers may be used for the following purposes:

[0198] Nanofibrous membranes for water purification treatment. Functionalized nanofibrous membranes can be used for remediation of wastewaters under visible light atmosphere

[0199] Air or gas filtration used in gas mask. Air filtration is conventionally performed by fibrous filters primarily due to their high collection efficiency also durability. The very high surface area facilitates adsorption and degradation of contaminants from air.

[0200] Protective clothing for chemical warfare agents. Chemical warfare agents in the battlefields are usually in the form of aerosol or vapors. Hence, protective systems such as clothing and face masks are highly needed to safeguard the people from an eventual chemical or biological hazard. Metal oxide nanofibrous mats can be applied into suitable protective clothing which is adaptability with the physiological conditions of the human body acting as a barrier against toxic and unwanted materials, such as aerosol particles, harmful vapors, and liquids.

[0201] One important discovery was found that for pre-calcined polymer fibers with different diameters, different rutile fractional crystal phase titanium fibers can be fabricated after the same calcination condition treatment and results in modification of the photocatalytic activity.

[0202] Over the past few years, it has been demonstrated that the electrospun titania nanofibers provide a faster photodegradation rates of Rhodamine B (Rh.B.), phenanzopyridine (PAP) and dimethyl methylphosphonate (DMMP) compared to conventional TiO.sub.2 nanoparticles. Besides that, many strategies have been also developed to fabricate several multifunctional nanofibrous materials to enhance their photocatalytic performance, among which photoactive dye supported anatase TiO.sub.2 and reduced graphene oxide TiO.sub.2 shows an excellent performance of degradation of Rh.B. and PAP under visible irradiation. These novel multifunctional materials offer excellent mobility of charge carriers for faster degradation and the possibility to exploit catalytic processes in real time decontamination.

[0203] Poly(3,4-ethylenedioxythiophene) or PEDOT is a conducting polymer based on 3,4-ethylenedioxythiophene (EDOT) monomer. It is transparent, and generally has high stability, a moderate band gap and low redox potential. PEDOT can be electrogenerated directly on a conductive support (Pt, Au, glassy carbon, indium tin oxide, . . . ) in organic solvents or in aqueous solution. In one study [Zhang, Xinyu; MacDiarmid, Alan G.; Manohar, Sanjeev K. (2005). Chemical synthesis of PEDOT nanofibers. Chemical Communications (42): 5328-30. doi:10.1039/b511290g. PMID 16244744] PEDOT nanofibers are produced from vanadium pentoxide nanofibers by a nanofiber seeding method. In this procedure EDOT is dissolved in an aqueous solution of camphorsulfonic acid (CSA) and a vanadium pentoxide nanofiber sol-gel and radical cationic polymerization is initiated by addition of ammonium persulfate. The resulting polymer precipitates from solution and has a general composition (PEDOT)(CSA)0.11-(HSO4)0.12(Cl)0.11(H2O)0.19. Washing with dilute hydrochloric acid removes the vanadium compound. The presence of the vanadium pentoxide seeds are believed to make the difference between the formation of PEDOT nanofibers (100 to 180 nanometer diameter and one to several micrometres long) and the formation of a more conventional granular morphology.

TABLE-US-00005 TABLE 7 Initial Metal Phase Composition Oxide (Rutile Fraction with the Materials balance of Anatase) Materials Compositions TiO.sub.2 8% TiO.sub.2-MOF Nanofibers Nanofibers ZnO 16% TiO.sub.2-PEDOT Nanofibers Nanofibers 38% TiO.sub.2N.sub.3 dye Nanofibers 67% TiO.sub.2-Reduced Graphene Oxide Nanofibers 97% TiO.sub.2Pt Nanofibers TiO.sub.2Pd Nanofibers

Example 4

[0204] The protection of the warfighter against chemical warfare agents (CWAs) and other biological and environmental toxins is essential on the modern battlefield. Nanotechnology can provide novel systems for rapid decontamination and protection through a self-cleaning mechanism.

[0205] Electromagnetic radiation in the form of visible light, ultra-violet light, or even sunlight can be used to achieve enhanced photodegradation of CWAs that are both rapid and inexpensive compared to the current decomposition techniques that are costly and time consuming. This technology takes advantage of advances in the fabrication of nanofibers activated by visible irradiation for targeted decontamination of CWAstechnology which can be used for the improvement of gas masks, for integration with conventional textiles for self-decontaminating garments, and for spray treatments of combat vehicles.

[0206] The protection of the warfighter against chemical warfare agents (CWAs) and other biological and environmental toxins is essential on the modern battlefield. Nanotechnology can provide novel systems for rapid decontamination and protection through a self-cleaning mechanism. Electromagnetic radiation in the form of visible light, ultra-violet light, or even sunlight can be used to achieve enhanced photodegradation of CWAs that are both rapid and inexpensive compared to the current decomposition techniques that are costly and time consuming. This technology takes advantage of nanofibers activated by visible irradiation for targeted decontamination of CWAs, technology which can be used for the improvement of gas masks, for integration with conventional textiles for self-decontaminating garments, and for spray treatments of combat vehicles.

[0207] The production of electrospun titania nanofibers provides an increase in surface area that elicits faster decomposition compared to conventional TiO.sub.2 nanoparticles. Self-assembled Metal Organic Frameworks (MOFs) may be combined with doped catalysts onto the titania, such as platinum, and used to further increase the rate of degradation. Introduction of noble metals to semiconductors permits creation of a rapid exchange of electrons to the electrolyte, improving the electronic properties of the catalyst. In addition, new tubular structures will be explored. A related but alternate approach is the production of structures such as zirconia and zinc oxide as approaches to increase the overall efficiency of decontamination.

[0208] TiO.sub.2 nanofibers represent an alternative approach to conventional composites for use in photocatalytic degradation. The one dimensional morphology of TiO.sub.2 is desired compared to spherical TiO.sub.2 nanoparticles; owing to excellent mobility of charge carriers, high surface area, the existence of pores enhancing the accessibility of electrodes to the hole transporting materials and hence enhanced charge collection and transport.

[0209] The nanofibrous materials were synthesized via a polyol synthesis, where platinum nanoparticles were deposited on TiO.sub.2 nanofibers, or with carbonaceous or graphitic materials. These were confirmed by EDX analysis, See FIG. 9A. The purpose of the modified catalyst was to affect the band gap energy of the TiO.sub.2, a lower energy would result in visible light exciting an electron from the conduction band to the valence band rather than ultraviolet irradiation.

[0210] Preliminary photocatalysis and degradation using the new materials was achieved utilizing in aqueous and non-aqueous solutions. Due to the toxicity and availability of chemical warfare agents, chemical analogs were used as an alternative. One common simulated chemical warfare agent (SCWA) of interest, 2-Chloroethyl ethyl sulfide, an analog for mustard gas, undergoes a hydrolysis mechanism in the presence of water. Therefore, it became difficult to determine if the degradation was occurring due to the radicals present in solution from the catalyst or the hydrolysis from the water, see FIGS. 24-27.

[0211] Photocatalysis experiments were modified to accommodate the necessary UV irradiation by performing the experiments in a quartz reaction vial. In previous experiments glass vials were being used as a reaction vessel however, for TiO.sub.2 to be a catalyst in photodegradation, electron-hole pairs must be formed. Without the energy of UV irradiation this becomes nearly impossible and therefore, no degradation will occur.

[0212] Dimethyl methyl phosphonate, a simulated chemical warfare agent for Sarin is being studied as a toxic pollutant. Preliminary studies showed DMMP was not susceptible to hydrolysis and therefore would be a better candidate for photocatalysis studies with TiO.sub.2 nanofibers. Results of the photocatalysis of DMMP with TiO.sub.2 nanofibers showed degradation of the pollutant in a one hour time span where TiO.sub.2 nanoparticles resulted in a 4 hour degradation time span, FIGS. 45 and 49. This also proved that nanofibers were better than nanoparticles and that surface to volume ratio plays a larger role in the photocatalytic degradation process than the surface area of nanoparticles.

[0213] All photocatalysts use incident irradiation in the UV or visible region of the spectrum to excite an electron from the valence band (leaving behind a hole) to the conduction band of a semiconductor. These photoinduced charge carriers then proceed to form reactive radicals, hydroxyl radicals (A) and super oxide radicals (D+) that attack adsorbed chemicals on the surface of the material, FIG. 8.

[0214] The electro spinning procedure may employ a sol gel solution in a 1:2 ratio of polymer to inorganic precursor, polymethylmethacrylate to titanium isopropoxide. A high voltage (25 kV/cm) is applied to the sol gel polymer solution. The sol gel is pulled through a metal needle as an electrified jet which collected on the counter electrode. The solvent evaporates as the fiber mat is deposited. Upon hydrolysis of the fiber mat will undergo a calcination process under thermally controlled atmospheric conditions producing the desired crystal structure of TiO.sub.2. At 400 centigrade for 4 hours anatase TiO.sub.2 nanofibers were produced, as shown in FIG. 23, which shows Anatase TiO.sub.2 nanofibers, diameter 30050 nm.

[0215] Due to the toxicity and availability of chemical warfare agents, chemical analogs will be used as an alternative. One common simulated chemical warfare agent (SCWA) of interest, 2-Chloroethyl ethyl sulfide, an analog for mustard gas, undergoes a hydrolysis mechanism in the presence of water. Preliminary studies have led to degradation experiments utilizing the fabricated catalyst in aqueous and non-aqueous solutions. .sup.13C NMR was used to examine the results of the degradation.

[0216] FIG. 24 shows .sup.13C NMR-Photocatalysis of 2CEES in a nucleophilic solvent with anatase TiO.sub.2 nanofibers. In the presence of catalyst and a non-nucleophilic solvent such as acetone the 4 characteristic peaks of 2-CEES were unaffected by the catalyst and UV irradiation. Resulting data was conducive with our knowledge and hypothesis that water will play a role in the degradation mechanism. Upon completion of degradation studies of varying non-nucleophilic solvents the experiments led to a 50:50 solution of water and acetone. 2-CEES may have some interaction with the water in the form of hydrolysis as well as the TiO.sub.2 acting as a catalyst for further degradation.

[0217] FIG. 25 shows .sup.13C NMR-Photocatalysis of 2CEES in an acetone/water solution with anatase TiO.sub.2 nanofibers. After standard experiments were done catalyst was added to the solution and the experiment was repeated. Minimal changes to degradation were seen in the presence of anatase TiO.sub.2 nanofibers. The presence of absorbed water is detrimental for the efficient use of TiO.sub.2 nanofibers as a catalyst.

[0218] After studying 2-Chloroethethyl sulfide in a variety or nucleophilic and non-nucleophilic solvents the experimental procedure was altered to a solvent-less system, where extractions in acetonitrile-d3 were done for .sup.13C NMR analysis. Below are the results pertaining to a degradation of 2-Chloroethyl ethyl sulfide with anatase TiO.sub.2 nanofibers.

[0219] FIGS. 26 and 27 show results for photocatalysis of 2CEES with anatase TiO.sub.2 nanofibers, without solvent, in a quartz vial. No change was seen over a twenty four hour period. The reaction mechanism of TiO.sub.2 was analyzed and showed that without the presence of absorbed water and oxygen, degradation would not occur. After the separation of electron-hole the absorbed water and oxygen will react the negative electron and positive hole creating superoxide and hydroxyl radicals. It is the presence of these radicals that initiate the degradation process. It is understood that 2-Chloroethyl ethyl sulfide hydrolyzes readily in water therefore it was necessary to be able to differentiate between the hydrolysis of 2-Chloroethyl ethyl sulfide and photodegradation. This led to an experiment where the TiO.sub.2 nanofibers were soaked in deionized water for 1 hour and excess water was removed prior to the addition of 2-Chloroethyl ethyl sulfide.

[0220] FIGS. 28 and 29 show photocatalysis of 2CEES in the presence of water saturated anatase TiO.sub.2 nanofibers without solvent, without and with UV irradiation in a quartz vial. After twenty four hours of UV irradiation, the 2-CEES completely degrades into its hydrolysis products where the sample being kept in the dark has no change over the same twenty four hour period.

[0221] FIGS. 30 and 31 show .sup.13C NMR-Photocatalysis of 2CEES with water saturated TiO.sub.2 nanofibers and silica gel over 24 hours of UV Irradiation. The resulting peaks after 24 hours of UV irradiation are consistent with peaks of 2CEES hydrolysis making it uncertain if TiO.sub.2 is playing a role in the hydrolysis process. Therefore, a control experiment was performed where silica gel replaced the TiO.sub.2 in the photocatalysis and the experiment was repeated.

[0222] It was surprising to see a change in 2-Chloroethyl ethyl sulfide while in the presence of silica gel. After 24 hours not only was there a change in the .sup.13C NMR but also a visible change in color, from clear to pale yellow. UV-Vis spectroscopy was performed on the final product. The sample was sealed and frozen for GC-MS analysis at a later date. Silica gel was also sent to ECBC for breakthrough testing.

[0223] FIG. 32 shows a UV-Vis analysis of photocatalysis product after 24 hours of UV irradiation with silica gel.

[0224] A 1 M solution was prepared of dimethyl methyl phosphonate in water. An aliquot was analyzed after hours 1, 4, 8, 24 and 72. The .sup.13C NMR showed no change after a 72 hour time period.

[0225] FIG. 33. shows a .sup.13C NMR-Hydrolysis study of Dimethylmethyl phosphonate over 72 hours. A control experiment was performed using standard Degussa P25 nanoparticles after 72 hours of UV irradiation yielded no change in the presence of anatase TiO.sub.2 nanofibers. Experimental conditions remained the same as previous trials the only changing variable was the shape of the catalyst. Concentration of solution remained constant at 1 M. After an 8 hour period of UV irradiation there was no change. One possible reason for no change is due to saturating the catalyst, leaving a large amount of excess pollutant in the solution; therefore, when aliquot samples were removed for analysis the excess DMMP was masking any degradation that could have been present in solution.

[0226] FIG. 34 shows .sup.13C NMR-Photocatalysis of DMMP with standard Degussa P25 nanoparticles in DI water over 8 hours of UV irradiation. The experiment was repeated at a lower concentration of 100 M, the rest of the experimental conditions remained the same except for UV irradiation ended after 4 hours.

[0227] FIG. 35 shows .sup.31P NMR-Photocatalysis of DMMP with anatase TiO.sub.2 nanofibers in water over 4 hours of UV irradiation. Results yielded a decrease in intensity over a 4 hour times period of UV irradiation.

[0228] Nanofibrous materials including metal supported nanoparticles on the surface of TiO.sub.2 nanofibers can be provided, by including the metal supported nanoparticles in the polyol mixture for electrospinning. SEM/EDX mapping can be used to characterize the final product. FIG. 22 shows SEM/EDX mapping of Pt nanoparticles (purple) supported on the surface of anatase TiO.sub.2 nanofibers.

[0229] FIGS. 36 and 37 show photocatalysis of 100 M solution dimethyl methylphosphonate with anatase TiO.sub.2 nanofibers in a 100 mL quartz beaker and a 16 ml quartz vial over 2 hours of UV irradiation. FIGS. 36 and 37 show that, after 2 hours of UV irradiation, a reaction vessel with a smaller volume showed a decrease in the signature phosphorus peak. The incident beam of UV irradiation was able to interact with the majority of the sample in the smaller beaker. This allowed for the generation of radicals to increase and react with the pollutant of interest.

[0230] Experiments comparing TiO.sub.2 nanofibers to nanoparticles as well as Pt nanoparticle doped TiO.sub.2 nanofibers were conducted. Pt nanoparticles displaced on the surface of TiO.sub.2 should allow for better separation of the electron hole pair under UV and visible irradiation without fear of recombination. Therefore, Pt nanoparticles were dispersed on anatase TiO.sub.2 nanofibers via the polyol synthesis:

##STR00002##

Polyol Synthesis of Pt Nanoparticles

[0231] These nanofibers were characterized and confirmed using SEM/EDX(mapping) and TEM as seen in FIGS. 9A and 22. FIG. 38 shows TEM imaging of Pt nanoparticles supported on the surface of anatase TiO.sub.2 nanofibers.

[0232] The PtTiO.sub.2 catalyst was then introduced to a 100 M solution of dimethyl methylphosphonate and underwent 4 hours of UV irradiation as seen in FIG. 39. The .sup.31P NMR was inconclusive; at 4 hours the signature peak for DMMP seemed to increase in intensity than decrease.

[0233] Diameter dependent photocatalysis experiments were also studied. It is hypothesized that the size of the grains that make up the nanofibers plays an important role in photodegradation. Therefore, anatase TiO.sub.2 nanofibers were electrospun with 2 different diameter sizes as seen in FIG. 40, which shows SEM (above) & TEM (bottom) images of 2 varying diameters of anatase TiO.sub.2 nanofibers ranging from 200 to 300 nm in diameter. These nanofibers were then introduced to a solution of Rhodamine B. in which UV-Vis spectroscopy was used to analyze the photodegradation process. According to Beer's Law, absorbance can be correlated to concentration of Rh.B.

[0234] The UV-VIS spectra correlated to the photodegradation of Phenazopyridine (PAP) in FIG. 41A shows the molecular formula of N3. FIGS. 41B and 41C show a UV-VIS spectrogram of N3 solution and UV-VIS of photodegradation of Phenazopyridine (PAP) using N3-sensitized TiO.sub.2 nanofiber (from left to right), respectively, showing almost no change when stirred in dark (T=45 to T=0). Upon UV irradiation the spectra changed near the wavelength of 428 nm which was confirmed to be pure PAP absorption peak. This means N3-dye sensitized TiO.sub.2 has the potential to be used as photocatalyst for degradation. FIG. 41D shows that the relative wide band gap of TiO.sub.2 limits its application as photocatalyst using under visible light illumination, but that various dyes have narrower band gaps.

[0235] After determining the importance of the inner filter effect with the quartz vial and quartz beaker using anatase TiO.sub.2 nanofibers, nanofibers and nanoparticles were compared. Degussa P25 nanoparticles were used, which are a standard TiO.sub.2 nanoparticle frequently used in literature for photocatalysis experiments. The same experimental conditions were used for each photocatalysis experiment and the results were compared. This can be seen in FIGS. 42 and 43. FIG. 42 shows photocatalysis of 100 M solution of dimethyl methylphosphonate with Degussa P25 TiO.sub.2 nanoparticles over 4 hours of UV irradiation. FIG. 43 shows photocatalysis of 100 M solution of dimethyl methylphosphonate with anatase TiO.sub.2 nanofibers over 2 hours of UV irradiation. After 2 hours of UV irradiation the signature peak for DMMP became undetectable using anatase TiO.sub.2 nanofibers where the Degussa P25 nanoparticles require 4 hours of UV irradiation before the signature peak for DMMP became undetectable. These results were confirmed by repetition of the experiment several more times.

[0236] The question arose of where the phosphorus was going after the results of the previous experiments were acquired. The phosphorus peak in the NMR was only decreasing in intensity and not shifting or reappearing anywhere else in the spectra. It was then hypothesized that the phosphorus was binding to the TiO.sub.2 catalyst and remaining bonded. This was attempted to be confirmed by Raman spectroscopy trying to find a TiP stretch of anatase TiO.sub.2 nanofibers before and after photocatalysis with DMMP, as shown in FIG. 44. The Raman spectra showed a possible (but unconfirmed) indicator for a PH or PH.sub.2 stretch.

Example 5

[0237] Polymethylmethacrylate (PMMA) fibers and PMMA/Titanium isopropoxide (TIP) fibers were created through an Electrospinning Procedure performed at 25 kV. The copper wire electrodes were separated by a distance of approximately 4 cm: Solution 1: 640 mg PMMA, 8 mL DMF, 1.32 mL TIP; and Solution 2: 640 mg PMMA, 8 mL DMF (no metal).

[0238] Two sol-gel solutions were synthesized. 640 mg PMMA was dissolved in 8 mL DMF for both solutions. However, in only one of the solutions was 1.32 mL Titanium isopropoxide added. Both solutions were added to glass pipettes and sequentially placed on a continuous copper wire which is connected to a high voltage supply source. The solutions were subjected to 25 kV, and once enough charge accumulated the polymer solution was drawn from the pipette to an aluminum foil collector. A dual jet setup for electrospinning polymer fiber blends was employed. FIG. 45 shows an SEM image of blended PMMA/PMMA:TIP polymer fibers. The two large fibers in the center of the image seem to have different surface morphologies and therefore, EDX/mapping was preformed to determine the elemental makeup of these fibers and to confirm distribution of titanium. This can be seen in FIGS. 46, 47 and 48. FIG. 46 shows EDX(mapping) polymer blended nanofibers where blue represents titanium distributed in the matrix. The blue represents the titanium present in the sample. We can tell there is slight Ti density dispersion. However, the density difference is not so significant. It is possible that the fibers might be wet during the spinning and they mix with each other slightly. Therefore, we cannot distinguish the fibers easily. The slight different Ti density dispersion also, might be a hint of our purpose to make a mesh of two types of fibers. FIG. 47 shows EDX(mapping) polymer blended nanofibers where green represents oxygen distributed in the matrix. FIG. 48. EDX(mapping) polymer blended nanofibers where red represents the carbon distributed in the matrix. The SEM images reveal titania dispersion throughout the fibers, making it difficult to discern those fibers with and without the titanium isopropoxide precursor.

[0239] Recently, attempts have been made to replicate the photocatalytic degradation of DMMP with TiO.sub.2 nanofibers and compare that to the literature standard of Degussa P25 nanoparticles. An experiment was unsuccessful in showing the signature DMMP .sup.31P NMR disappear in only 1 hour, as shown in FIG. 49, which shows .sup.31P NMR of the photodegradation of 100 M DMMP with TiO.sub.2 nanofibers. However, the P25 nanoparticles showed data consistent with previous results. This implies that the nanofibers were the source of variation in results.

[0240] FIGS. 50A and 50B shows that the photocatalytic degradation process is a first-order reaction, and that Anatase/RGO has a higher initial rate constant (k=0.0384 min.sub.1) than pure anatase nanoparticles (k=0.0301 min.sup.1) during the first 30 mins degradation.