Controlled release of hydrogen from composite nanoparticles

Abstract

Multi-functional materials for use in reversible, high-capacity hydrogen separation and/or storage are described. Also described are systems incorporating the materials. The multi-functional materials combine a hydrogen-absorbing material with a high-efficiency and a non-contact energy-absorbing material in a composite nanoparticle. The non-contact energy-absorbing material include magnetic and/or plasmonic materials. The magnetic or plasmonic materials of the composite nanoparticles can provide localized heating to promote release of hydrogen from the hydrogen storage component of the composite nanoparticles.

Claims

1. A multi-functional nanoparticle for hydrogen storage or separation and controlled hydrogen release comprising: a magnetic nanoparticle having a size of from about 1 nanometer to about 500 nanometers; and a nanosized particle having a size of from about 1 nanometer to about 100 nanometers deposited on a surface of the magnetic nanoparticle and in thermal contact with the magnetic nanoparticle, the nanosized particle comprising a reversible metal hydride that forms a first interstitial hydride with a first isotope of hydrogen and that forms a second interstitial hydride with a second isotope of hydrogen, wherein the first isotope of hydrogen is released from the first interstitial hydride at a first release condition and the second isotope of hydrogen is released from the second interstitial hydride at a second, different release condition.

2. The multi-functional nanoparticle of claim 1, wherein the magnetic nanoparticle is in direct contact with the reversible metal hydride of the nanosized particle.

3. The multi-functional nanoparticle of claim 1, wherein the magnetic nanoparticle is in the shape of a sphere, a tube, a ring, or a rod.

4. The multi-functional nanoparticle of claim 1, the magnetic nanoparticle comprising at least one of iron, nickel, gadolinium, and cobalt.

5. The multi-functional nanoparticle of claim 4, the magnetic nanoparticle comprising Fe.sup.2+ and/or Fe.sup.3+.

6. The multi-functional nanoparticle of claim 1, the reversible metal hydride comprising palladium, titanium, zirconium, hafnium, zinc, or vanadium.

7. The multi-functional nanoparticle of claim 1, wherein the reversible metal hydride has a compositional formula of:
A.sub.1-xM.sub.xT.sub.5-y-zB.sub.yC.sub.z, wherein: A=La; M=La, Pr, Nd or Ce; T=Ni; B=Co; C=Mn, Al or Cr; x=0.0 to 1.0; y=0.0 to 2.5; and z=0.0 to 1.0.

8. A system for controlled release of hydrogen from a hydrogen-absorbing material comprising: a bed comprising a plurality of the multi-functional composite nanoparticles of claim 1; and an energy source in non-contact communication with the multi-functional composite nanoparticles, wherein the energy source is configured to emit an alternating magnetic field in the non-contact communication.

9. The system of claim 8, further comprising a hydrogen source upstream of the bed, wherein the hydrogen source is a source of the first isotope of hydrogen and the second isotope of hydrogen.

10. The system of claim 8, further comprising a hydrogen collection or hydrogen combustion facility downstream of the bed.

11. The system of claim 8, wherein the energy source is configured to vary the alternating magnetic field.

12. A multi-functional nanoparticle for hydrogen storage or separation and controlled hydrogen release comprising: a plasmonic nanoparticle having a size of from about 1 nanometer to about 500 nanometers; and a nanosized particle having a size of from about 1 nanometer to about 100 nanometers deposited on a surface of the plasmonic nanoparticle and in thermal contact with the plasmonic nanoparticle, the nanosized particle comprising a reversible metal hydride that forms a first interstitial hydride with a first isotope of hydrogen and that forms a second interstitial hydride with a second isotope of hydrogen, wherein the first isotope of hydrogen is released from the first interstitial hydride at a first release condition and the second isotope of hydrogen is released from the second interstitial hydride at a second, different release condition.

13. The multi-functional nanoparticle of claim 12, wherein the plasmonic nanoparticle is in the shape of a sphere, a tube, a ring, or a rod.

14. The multi-functional nanoparticle of claim 12, the reversible metal hydride comprising palladium, titanium, zirconium, hafnium, zinc, or vanadium.

15. The multi-functional nanoparticle of claim 12, wherein the metal hydride has a compositional formula of:
A.sub.1-xM.sub.xT.sub.5-y-zB.sub.yC.sub.z, wherein: A=La; M=La, Pr, Nd or Ce; T=Ni; B=Co; C=Mn, Al or Cr; x=0.0 to 1.0; y=0.0 to 2.5; and z=0.0 to 1.0.

16. The multi-functional nanoparticle of claim 12, the plasmonic nanoparticle comprising gold, platinum, silver, copper, and/or aluminum.

17. A system for controlled release of hydrogen from a hydrogen-absorbing material comprising: a bed comprising a plurality of the multi-functional composite nanoparticles of claim 12; and an energy source in non-contact communication with the multi-functional composite nanoparticles, wherein the energy source is configured to emit an electromagnetic wave in the non-contact communication.

18. The system of claim 17, further comprising a hydrogen source upstream of the bed, wherein the hydrogen source is a source of the first isotope of hydrogen and the second isotope of hydrogen.

19. The system of claim 17, further comprising a hydrogen collection or hydrogen combustion facility downstream of the bed.

20. The system of claim 17, wherein the energy source is configured to emit an electromagnetic wave in the near infra-red or visible spectrum.

21. The system of claim 20, wherein the energy source is configured to vary the emission of the electromagnetic wave.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) A full and enabling disclosure of the present subject matter, including the best mode thereof to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures in which:

(2) FIG. 1 schematically illustrates a prior art system for storing hydrogen in a solid-state form.

(3) FIG. 2 schematically compares bulk heating to localized thermal heating as is possible by use of disclosed composite nanoparticles.

(4) FIG. 3 illustrates a system during which heat produced by absorption of energy by the magnetic or plasmonic component of a composite nanoparticle can be used to heat a hydrogen absorbing component of the composite nanoparticle and thereby release absorbed hydrogen.

(5) FIG. 4 is a scanning electron microscope (SEM) image of Fe.sub.2O.sub.3 spheres used in formation of composite nanoparticles.

(6) FIG. 5 is an SEM image of Fe.sub.2O.sub.3 tubes used in formation of composite nanoparticles.

(7) FIG. 6 is an SEM image of Fe.sub.2O.sub.3 wires used in formation of composite nanoparticles.

(8) FIG. 7 is an SEM image of Fe.sub.2O.sub.3—Pd composite nanoparticles.

(9) FIG. 8 is an SEM backscattering image of the Fe.sub.2O.sub.3—Pd composite nanoparticles of FIG. 7.

(10) FIG. 9 illustrates an energy dispersive X-ray (EDX) analysis of the Fe.sub.2O.sub.3—Pd composite nanoparticles of FIG. 7.

(11) FIG. 10 presents infrared thermal imaging of Fe.sub.2O.sub.3 nanoparticles prior to, during, and following heating for 20 minutes by an alternating magnetic field.

(12) FIG. 11 illustrates the effect of nanoparticle concentration on magnetic heating characteristic of a suspension of composite nanoparticles.

(13) FIG. 12 illustrates the effect of nanoparticle concentration on the specific power loss of a suspension of composite nanoparticles.

(14) FIG. 13 illustrates the effect of nanoparticle composition on magnetic heating characteristics of a suspension of the nanoparticles.

(15) FIG. 14 illustrates the effect of nanoparticle composition on the specific power loss of a suspension of the nanoparticles.

(16) FIG. 15 illustrates the effect of nanoparticle shape on magnetic heating characteristic of a suspension of the nanoparticles.

(17) FIG. 16 schematically illustrates the hydrogen loading approach for loading hydrogen onto the composite nanoparticles.

(18) FIG. 17 is a photograph shown a capillary loaded with nanoparticles configured for exposure to a magnetic field.

(19) FIG. 18 illustrates the effect of magnetic field strength on hydrogen release characteristics as determined by measurement of hydrogen gas pressure for a capillary loaded with Fe.sub.2O.sub.3—Pd composite nanoparticles.

(20) FIG. 19 illustrates the effect of temperature on pressure of a composite nanoparticle system in the presence of hydrogen as compared to a control nanoparticle system.

(21) FIG. 20 illustrates hydrogen gas desorption by use of magnetic induction heating from Fe.sub.2O.sub.3—Pd composite nanoparticles as compared to control Fe.sub.2O.sub.3 nanoparticles.

(22) FIG. 21 illustrates the variation in hydrogen desorption characteristics from composite nanoparticles for different hydrogen isotopes.

(23) Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.

DETAILED DESCRIPTION

(24) Reference will now be made in detail to various embodiments of the disclosed subject matter, one or more examples of which are set forth below. Each embodiment is provided by way of explanation of the subject matter, not limitation thereof. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made in the present disclosure without departing from the scope or spirit of the subject matter. For instance, features illustrated or described as part of one embodiment, may be used in another embodiment to yield a still further embodiment.

(25) In general, the present disclosure is directed to materials for use in reversible, high-capacity hydrogen separation and/or storage, systems incorporating the materials, and methods for using materials. More specifically, disclosed multi-functional materials combine a hydrogen absorption material with a high-efficiency non-contact energy absorption material in a composite nanoparticle. The composite nanoparticles can be used in fields that can utilize hydrogen separation and/or storage. For instance, disclosed materials can be utilized in non-contact separation of hydrogen from other analytes, as well as in separation of hydrogen isotopes from one another. The materials can find applications in sensing, manipulation and photothermal destruction of analytes, catalytic processes, biological imaging and magnetic manipulation, hyperthermia applications, and as energy storage materials, among others.

(26) During use, energy can be generated and delivered in a non-contact approach to an energy-absorbing component of the composite nanoparticle. This component can then release the absorbed energy in the form of heat, which can increase the temperature of the hydrogen absorbing material and promote the targeted and controlled release of hydrogen gas from the hydrogen absorbing component of the composite nanoparticle. The energy absorbing component can include a magnetic material that can absorb energy when placed in an alternating magnetic field or can include a plasmonic material that can absorb energy when contacted with an electromagnetic wave of a suitable wavelength (e.g., light), or can include a combination of energy-absorbing materials.

(27) Depending upon the particular characteristics of the energy absorbing component of the nanoparticles, the rate and amount of hydrogen released from the composite nanoparticles can be controlled by varying the magnetic field strength, for instance by varying the current in a coil, or by varying the intensity of the electromagnetic wave, for instance by varying the wavelength of the light. In one embodiment, the controlled hydrogen release afforded by the technology can be employed to selectively release hydrogen isotopes. This can provide a viable and simple alternative to existing technology for both hydrogen separation and storage. Disclosed systems can be easy and straightforward to implement and can replace existing systems such as bulky hot/cold nitrogen systems or electric heaters that have been utilized in the past.

(28) Disclosed systems can also be designed with a very small footprint, which can provide a safer method of storing and handling explosive—and in some embodiments, radioactive—hydrogen isotopes. For instance, when considering use in separation of tritium in the nuclear power industry, the development of a small storage and separation bed could lower costs due to physically smaller design requirements and could also enhance safety by minimizing the amount of tritium in the system at any one time.

(29) The hydrogen storage and release systems can also be highly efficient, as the composite materials can promote fast hydrogen kinetics and efficient “on demand” temperature control. Efficiency can also be gained as the energy input to a system can be non-contact, selective, localized, and targeted, which can encourage rapid heating and cooling of the composite materials (for instance about 50° C./sec in some embodiments) while the surrounding area need not be subjected to excessive wasted heat, thereby minimizing temperature of the surroundings.

(30) The composite materials are provided as nanoscale materials. As utilized herein, the term “nanoparticles” is intended to refer to particles for which the largest average cross-sectional dimension of the particle may range from about 1 nanometer to about 1 micrometer, in some embodiments from about 1 nanometer to about 100 nanometers, and in some embodiments, from about 50 nanometers to about 500 nanometers. The shape of the composite particles may also generally vary as desired. For example, in some embodiments, the particles may have the shape of a sphere, plate, rod, disc, bar, tube, irregular shape, etc. In some embodiments, examples of which are discussed further herein, the shape and size of the particle can be utilized to control hydrogen absorption and desorption characteristics.

(31) The nanoscale size of the composite particles can be beneficial, as this can promote fast hydrogen exchange by shortening diffusion distances. Bulk porous materials can exhibit a larger penetration depth of the hydride reaction into the bulk, which increase both the hydrogen absorption and desorption times. In addition, the composite nanoparticles can exhibit higher kinetics of gas uptake and release as compared to bulk porous materials, such as bulk polymicrocrystalline materials.

(32) The composite nanoparticles include a first material that can absorb energy provided in a non-contact fashion and efficiently convert and re-emit at least a portion of that absorbed energy as thermal energy. The non-contact energy absorption and conversion capability of this material allows for heat generation of the system to be highly localized and better controlled as compared to hydrogen storage materials that are conventionally heated in a bulk thermal treatment approach. As schematically illustrated in FIG. 2, conventional heating (left) occurs from the application of thermal energy to the outside of a storage facility or container and bulk transport of the thermal energy toward the center of the contents held in the container, leading to an increase in temperature of the total internal environment and the surroundings. In localized thermal heating as shown in the right panel of FIG. 2, heating can be carried out with each composite nanoparticle acting as is its own source of heat, controlled by the non-contact absorption of energy in a non-thermal form, and as such, the surroundings are minimally heated, as the non-thermal energy source will heat only the particles with limited heating of the surroundings. This leads to a smaller energy footprint for a system, as well as much greater control of the heating.

(33) In one embodiment, the composite nanoparticles can include a magnetic material. In general, any magnetic material capable of absorbing energy in the presence of an alternating magnetic field and re-emitting at least a portion of that energy as heat is encompassed, as demonstrated in FIG. 3. For instance, a magnetic material can include, but is not limited to, rare earth metals such as gadolinium, terbium, dysprosium, holmium, etc.; transition metals such as iron, nickel, cobalt, magnesium, etc.; noble metals such as rhodium, palladium, etc. In one embodiment, the magnetic material can include at least one of iron, nickel, and cobalt. Examples of magnetic materials include those including Fe, Ni, Co, NiCo, FeZn, borides of these materials, ferrites, rare-earth metals, or alloy combinations thereof. The magnetic materials can be present in any suitable form including, without limitation, in the form of oxides, compositions, combinations, solid dispersions, and alloys, such as Gd.sub.5Si.sub.4, Gd.sub.5Si.sub.2.06Ge.sub.1.94, Gd.sub.7Pd.sub.3; MnFeP.sub.0.35As.sub.0.65, and MnAs.

(34) In one particular embodiment, an iron-based magnetic material, including Fe.sup.2+ and/or Fe.sup.3+, can be utilized in a suitable form including, but not limited to, compositions, complex oxides, alloys, solid dispersions and other combinations; for instance with elements of Group IV, including, but not limited to, lead, zirconium, titanium, tin, optionally doped by small amounts of the elements of the III and V groups, such as scandium and niobium.

(35) The composite nanoparticles can include a plasmonic material capable of absorbing energy in the presence of a suitable electromagnetic wave and re-emitting at least a portion of that energy as heat. In one embodiment, the composite nanoparticles can include either a magnetic material or a plasmonic material, but the composite nanoparticles are not limited to this and can optionally include a combination of different types of energy-absorbing materials (e.g., both magnetic and plasmonic), as well as multiple examples one or both types of energy-absorbing materials (e.g., one or more magnetic materials and/or one or more plasmonic materials).

(36) Plasmonic materials generally include at least one of gold, platinum, silver, aluminum, copper, or another noble metal. Plasmonic nanoparticles are capable of coupling with electromagnetic radiation (e.g., in the near infrared (e.g., about 700 nm to about 1 mm) or visible (e.g., about 400 nm to about 700 nm) wavelength) for localized heating. The effect of electromagnetic waves of a suitable wavelength upon the nanoparticles is such that a resonant oscillation of the electrons is activated in the nanoparticles (plasmons), which, due to their small size, then dissipate the energy as heat into the local environment. The plasmonic resonance can be tuned through modification of the size, shape, morphology, plasmonic material, and additional materials of the particles (e.g., a gold or silver coating on a core) to react to specific wavelengths of electromagnetic radiation. For instance, gold and silver nanoparticles will typically have resonance peaks in the visible near-IR spectrum, whereas gold-coated silicon nanoparticles can be tuned to resonate when excited by Near Infra-Red (NIR) radiation.

(37) Nanosized particles coupled to a magnetic and/or plasmonic material can be prepared using any of a variety of known technologies. For example, nanoparticles can be formed by the plasma method in inert medium (for example, under argon) from particles of a larger initial size, for example, 50-100 microns, by templated growth methodologies, by ionic deposition and growth methodologies, by chemical reduction, etc.

(38) In conjunction with the energy absorbing magnetic or plasmonic material, the composite nanoparticles also include a hydrogen-absorbing material that can absorb and release hydrogen according to a thermal control mechanism. In one embodiment, the reversible hydrogen-absorbing material can be one that is capable of forming a metal bond with hydrogen according to an interstitial hydride formation methodology.

(39) In general, the hydrogen-absorbing material can be a crystalline or amorphous material formed of any metal or metal alloy capable of reversibly storing hydrogen within the matrix. By way of example, the reversible hydrogen-absorbing material can include, without limitation, an element chosen from Group IA alkali metals, Group IIA alkali earth metals, Group IIIB lanthanides, or Group IVB transition metals. In one embodiment, the hydrogen-absorbing material can include a transition metal capable of forming a reversible binary metal hydride including, without limitation, palladium, titanium, zirconium, hafnium, zinc, and/or vanadium.

(40) Multi-component metal alloys are also encompassed as reversible hydrogen-absorbing materials and can include, without limitation, combinations of Group IV elements with Group V through Group XI elements (based on the 1990 IUPAC system, in which the columns are assigned the numbers 1 to 18), as well as alloys including combinations of lanthanides (atomic numbers 58 to 71) with Group VII through Group XI elements. For example, the hydrogen-absorbing material can have the structure A.sub.xT.sub.y in which A can be one or more Group IV elements and T can be one or more Group V through Group XI elements. In some embodiments, a Group VI metal can be selected from Mo and W, and a Group VIII metal can be selected from Fe, Co, Ni, Pd, and Pt. In some embodiments, a Group VI metal can be Mo and a Group VIII metal can be selected from Co and Ni.

(41) In another embodiment, the hydrogen-absorbing material can have a compositional formula of
A.sub.1-xM.sub.xT.sub.5-y-zB.sub.yC.sub.z,

(42) wherein: A=is an alloy of rare earth elements, typically including cerium and lanthanum; M=La, Pr, Nd or Ce; T=Ni; B=Co; C=Mn, Al or Cr; x=0.0 to 1.0; y=0.0 to 2.5; and z=0.0 to 1.0.

(43) The hydrogen-absorbing material can be selected to have a desired lattice structure and thermodynamic properties, such as to control the pressure and/or temperature at which it can absorb and desorb hydrogen. These working thermodynamic parameters can be modified and fine-tuned by an appropriate alloying method, and as such, the composition of the composite nanoparticles can be designed for use in a particular process.

(44) The hydrogen-absorbing material and the magnetic or plasmonic materials are combined such that the two are in thermal communication with one another, i.e., thermal energy radiated from the magnetic or plasmonic material can be transferred to the hydrogen-absorbing material leading to a temperature increase, thereby facilitating desorption of stored hydrogen. As such, the materials can be in direct or indirect contact with one another and combined in any morphology or fashion so as to maintain the thermal communication. For instance, in one embodiment, the composite materials can be provided as core/shell composite nanoparticles in which the shell material either partially or completely covers the core material. The particular arrangement of the materials is not critical, as long as each is capable of carrying out the desired function. For instance, the core of a core/shell composite nanoparticle can be formed of either the hydrogen-absorbing material or the magnetic or plasmonic material, as long as each component can carry out the desired function (e.g., hydrogen can reach and be absorbed by the hydrogen-absorbing material).

(45) In one embodiment, the magnetic or plasmonic nanoparticles can be first formed, and the hydrogen-absorbing material can be deposited on all or on a portion of the surface of the nanoparticles; for instance, via a wet chemistry formation process as described further in the examples section below.

(46) The energy absorption and localized heating provided by the magnetic or plasmonic materials can be self-controlled based on characteristics of the particles themselves in addition to modification of aspects of the input energy (magnetic field strength, electromagnetic wavelength, etc.). For instance, the heating characteristics of a magnetic nanoparticle can be controlled according to the Curie temperature of the magnetic material. Non-contact heating of the composite nanoparticles can be controlled by altering the nanoparticle composition, size, shape and/or concentration in the local area. Depending upon the composition and morphology of the particular materials included in the composite nanoparticles, the heating characteristics of the energy-absorbing material may or may not vary with the presence or amount of the hydrogen-absorbing material. For instance, the heating characteristics of a magnetic nanoparticle may be independent of the presence of a metallic domain that functions as the hydrogen-absorbing material.

(47) The tunability of the composite nanoparticles allows selective control of the input energy (the magnetic field strength or the wavelength of electromagnetic radiation) required to cause the nanoparticles to heat the local area. For instance, at least one of the size and shape of the composite nanoparticles, as well as the particulars of the magnetic or plasmonic material incorporated in the composite nanoparticles, may be configured to particular design specification. For instance, when considering nanoparticles that include a plasmonic material, the size, shape, and other characteristics of the nanoparticles can be configured such that the composite nanoparticles exhibit the desired plasmon resonance when exposed to one or more of ultraviolet, visible, and infrared radiation. For example, when considering non-spherical plasmonic nanoparticles, the heating characteristics can vary depending upon the alignment of an axis of the particles with a polarization axis of the incident electromagnetic radiation. As such, the shape and arrangement of the nanoparticles can be controlled so as to utilize this dependence to advantage in system design.

(48) FIG. 3 illustrates one system that contains magnetic-based composite nanoparticles. As shown, when the system is not placed under a magnetic field (as in the left panel), the temperature of the nanoparticles is low and the hydrogen can be stored as an interstitial hydride in the hydrogen-absorbing material of the composite nanoparticles. In the presence of an oscillating magnetic field (right panel), the magnetic nanoparticles can act as a local “hot-spot” to heat up the surrounding environment via hysteresis loss or relaxation mechanisms. This occurs because the magnetic moments of the nanoparticles change direction to line up with the external field, which can cause local heating. This change of direction can take place two different ways: 1) Brownian relaxation, where the nanoparticle physically rotates so the moment lines up with the external field; and 2) Neel relaxation, where the particle is stationary, but the magnetic moment rotates in the fixed lattice. A plasmonic-based system can function in a similar fashion with electromagnetic radiation of a predetermined wavelength utilized as the energy source.

(49) By use of disclosed systems, heat delivered from the magnetic or plasmonic material to the hydrogen-absorbing material can be modulated by suitable selection of characteristics of the alternating electromagnetic or plasmonic field, such as amplitude and frequency of the alternating magnetic field, shape of the magnetization curve, plasmonic field power, etc. Further system control can be obtained through placement of the composite nanoparticles with respect to the non-contact energy source. For instance, the composite nanoparticles can be selectively placed in regions where heat is necessary and energy input can be adjusted to generate the desired amount of heat in a controlled manner.

(50) In one embodiment, the hydrogen-absorbing material can show variation in absorption and/or desorption characteristics with regard to different isotopes of hydrogen. For instance, and as described further in the examples below, a hydrogen absorbing material, such as palladium, can exhibit selectivity of desorption of hydrogen vs. tritium based upon the temperature and/or pressure of the system. As such, by controlling the desorption characteristics of the system, e.g., the pressure and/or temperature of the system, one of the hydrogen isotopes can be selectively desorbed over the other. This can be beneficially utilized to separate the hydrogen isotopes. Likewise, the hydrogen isotopes can show preferential absorption characteristics depending upon a characteristic of the system, e.g., temperature as controlled by field strength, etc. In this embodiment, one isotope can show preferential absorption characteristics, and the isotopes can be separated at this stage of a separation process.

(51) The present disclosure may be better understood with reference to the Examples set forth below.

Example 1

(52) Hybrid Fe.sub.2O.sub.3—Pd nanoparticle conjugates were prepared for magnetically-induced hydrogen release. The Fe.sub.2O.sub.3 provided magnetic functionality, whereas the Pd provided hydrogen absorption. Fe.sub.2O.sub.3 nanoparticles were utilized as purchased. FIG. 4-FIG. 6 illustrate Fe.sub.2O.sub.3 spheres (FIG. 4), tubes (FIG. 5), and wires (FIG. 6) used to form composite nanoparticles.

(53) Pd regions were synthesized on the Fe.sub.2O.sub.3 nanoparticles using a wet chemical approach at ambient conditions. Briefly, 0.125 mmoles Fe.sub.2O.sub.3, 0.08 mmol CTAB, 0.12 mmoles NaPdCl.sub.4 in 20 mL diH.sub.2O was heated to 80° C. before 0.14 mmoles L-ascorbic acid was added and the solution turned black. The solution was heated at 80° C. for 30 minutes before being cooled and magnetically purified three times. The final Fe.sub.2O.sub.3—Pd materials were suspended in water. FIG. 7 is an SEM image of the Fe.sub.2O.sub.3—Pd composite nanoparticles.

(54) Pd was successfully grafted onto Fe.sub.2O.sub.3 spheres, as indicated by SEM backscattering image (FIG. 8) in which darker regions indicate the presence of the Pd, and EDX measurements (FIG. 9).

(55) Table 1, below, provides the quantitative weight percent measurements obtained from the EDX analysis. The K, L, and M symbols refer to the atomic shell that the ejected electrons originated from. This is standard X-ray notation for the atomic principle energy level (K=1, L=2, M=3, etc.).

(56) TABLE-US-00001 TABLE 1 Element Weight % C K 1.59 O K 0.96 Al K 0.18 Fe K 0.60 Cu L 1.53 Pd L 12.86 Au M 0.19 Total 17.93

Example 2

(57) Magnetic and composite magnetic nanoparticles were examined for non-contact absorption of magnetic energy and subsequent release thereof as heat. To that end, suspensions of Fe.sub.2O.sub.3 and Fe.sub.2O.sub.3-metal conjugates were placed in a magnetic field using a 425 kHz water-cooled copper coil, and the temperature increase in the presence of the magnetic field was measured. FIG. 10 shows the evolution of the heat in a vial of Fe.sub.2O.sub.3 nanoparticles using infrared thermal imaging. The images were taken prior to being placed in a magnetic field, and then 1 minute, 10 minutes, and 20 minutes after heating as shown in FIG. 10. The lower image presents a side view of the vial after 20 minutes of heating. As shown, following heating, the hottest (darkest on FIG. 10) point of the vial was in the middle, where most of the nanoparticles had accumulated and it had reached about 63° C.

(58) Effect of variation in nanoparticle concentration on heating rate and ultimate temperature attained, as well as specific power loss of the system, was also examined. Results are shown in FIG. 11 and FIG. 12. As shown, the concentration of the Fe.sub.2O.sub.3 nanoparticles affected the temperature reached by the solution (FIG. 11) but didn't affect the efficiency of heating, as indicated by the calculation of the specific loss power (SLP) (FIG. 12).

(59) The effect of the metal island growth on the magnetic hyperthermia of Fe.sub.2O.sub.3 nanoparticles was also investigated. As shown in FIG. 13, the temperature was not affected by the growth of different metal domains including a Pd metal domain and an Au metal domain. As shown in FIG. 14, the SLP remained unchanged with the growth of the gold domain, but decreased slightly for the Fe.sub.2O.sub.3—Pd sample, indicating a slight loss of heating efficiency. This could be due to loss of Fe.sub.2O.sub.3 (either through sample preparation or NP etching) compared to the Fe.sub.2O.sub.3—Au sample, from the growth of the Pd onto the Fe.sub.2O.sub.3, or from more heat loss compared to the other samples.

(60) The effect of nanoparticle shape on magnetic hyperthermia was also investigated. Results are shown in FIG. 15. The Fe.sub.2O.sub.3 spheres heated up significantly in the magnetic field, whereas the tubes, rings, and wires showed a minimal (2.5° C.) increase in temperature in the magnetic field.

Example 3

(61) Fe.sub.2O.sub.3—Pd composite nanoparticles formed as described above were examined to confirm that absorbed hydrogen could be released in a controlled manner when placed in a magnetic field by simply changing the experimental conditions, e.g. magnetic field strength. For these experiments, Fe.sub.2O.sub.3—Pd composite nanoparticles were loaded into capillary tubes by depositing the nanoparticles on the interior walls of the capillaries as a thin layer. As such, the nanoparticles did not fill the capillary. Each capillary was loaded with approximately 20 mg of the composite nanoparticles having a weight ratio of Pd to Fe of 0.6. The capillary tubes had a length of 20.3 cm and a volume of 0.101 cm.sup.3. Following deposition of the nanoparticles on the interior surface of the capillaries, the nanoparticles were loaded with hydrogen by flowing H.sub.2 gas through the capillaries. In these studies, Fe.sub.2O.sub.3 particles loaded into separate capillaries were used as a control. FIG. 16 schematically illustrates the hydrogen loading approach and an image of Fe.sub.2O.sub.3—Pd and control Fe.sub.2O.sub.3 capillaries. The arrow in FIG. 16 is pointing to the capillaries in which material was deposited.

(62) Following H.sub.2 loading, the capillaries were placed in a coil as described above that exposed them to an alternating magnetic field, as shown in FIG. 17.

(63) The change in pressure in a capillary containing hydrogen (H.sub.2)-loaded Fe.sub.2O.sub.3—Pd composite nanoparticles was measured at various magnetic field strengths as a measure of hydrogen release from the nanoparticles. As shown in FIG. 18, the H.sub.2 release increased (as determined by increasing pressure) with increasing magnetic field strength. The temperature of the capillary was measured using infrared thermal imaging. The inset of FIG. 18 illustrates an infrared thermal image of a capillary during heating held in a coil at 70% power (Current=13.3 A, T=112° C.). These data show that the rate of hydrogen release could be controlled by altering the strength of the magnetic field.

(64) The strength of the magnetic field was calculated using the following equation:
B=μnI

(65) in which B=magnetic field strength μ=permeability (1.26×10.sup.−6 H/m for Cu coil) n=turns/meter (6 turns in 3.4 cm; n=133 turns/m) I=current (Amps)

(66) Table 2, below provides the calculated magnetic field strengths and initial hydrogen release rate at the different power levels examined:

(67) TABLE-US-00002 TABLE 2 Power Current B B Initial rate (%) (A) (Tesla) (Gaussians) (psi/s) 40 2.4 4.02 × 10.sup.−4 4.02 3.20 × 10.sup.−3 50 6.4 1.07 × 10.sup.−3 10.7 1.25 × 10.sup.−2 60 9.9 1.66 × 10.sup.−3 16.6 1.52 × 10.sup.−2 70 13.3 2.23 × 10.sup.−3 2.23 2.01 × 10.sup.−2 80 16.3 2.73 × 10.sup.−3 27.3 3.56 × 10.sup.−2

(68) The effect of temperature on H.sub.2 pressure was measured in the capillaries using a pressure transducer. As shown in FIG. 19, the pressure of the two capillaries (composite and control) decreased when the temperature was decreased using dry ice (T˜−78° C.). The difference in pressure for the Fe.sub.2O.sub.3—Pd nanoparticle-loaded capillary compared to the Fe.sub.2O.sub.3 nanoparticle-loaded capillary is evidence that there is hydrogen absorption by the composite nanoparticles. The capillaries were allowed to reach room temperature, and the final pressure of the Fe.sub.2O.sub.3—Pd nanoparticle-loaded capillary was lower than the Fe.sub.2O.sub.3 control. Repeat measurements show that the absorption and desorption was reversible and consistent.

(69) FIG. 20 shows the hydrogen release of the samples in using an alternating magnetic field as the heat source. The pressure of the Fe.sub.2O.sub.3—Pd composite nanoparticle-loaded capillary increased while the Fe.sub.2O.sub.3 nanoparticle-loaded capillary remained constant, showing that the Fe.sub.2O.sub.3—Pd composite nanoparticles were able to absorb and release hydrogen using an alternating magnetic field.

(70) Hydrogen absorption and release studies were measured using a magnetic-induced hyperthermia setup that was attached to a residual gas analyzer (RGA) to determine the components in the gas. In aqueous studies, steam was produced when the nanoparticles were exposed to an alternating magnetic field, proving that the nanoparticles were heating in response to the magnetic energy. In aqueous studies, the temperature increase was measured using a fiber optic temperature probe.

Example 4

(71) Fe.sub.2O.sub.3—Pd composite nanoparticles formed as described above were examined for differential hydrogen absorption/desorption based upon hydrogen isotope. As shown in FIG. 21, H.sub.2 and D.sub.2 displayed a different plateau pressure and different absorption capacities for the same composite nanoparticles and under the same magnetic field. As such, disclosed materials can be utilized in separation of hydrogen isotopes.

(72) While certain embodiments of the disclosed subject matter have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the subject matter.