Coating layers of a nanocomposite comprising a nano-cellulose material and nanoparticles

Abstract

The invention provides articles and methods for making such articles including a substrate coated on at least one region thereof with a layer of nanocomposites nano-cellulose materials and nanoparticles.

Claims

1. A multilayer sheet comprising at least one layer of a nanocomposite blend of NCC and a plurality of nanoparticles, wherein said at least one layer of the nanocomposite blend is provided optionally between two layers or sheets of a substrate material, said multilayer sheet suppressing or blocking UV or IR radiation and permeation therethrough of gases selected from O.sub.2, CO.sub.2, CO, N.sub.2, NO.sub.x, SO.sub.x and H.sub.2, and wherein the nanoparticles are selected from the group consisting of ZnO, Al.sub.2O.sub.3, SiO.sub.2, CdSe, TiO.sub.2, doped TiO.sub.2, quantum dots and combinations thereof.

2. The sheet according to claim 1, wherein said at least one layer of a nanocomposite having a thickness of between 5 to 1000 nm, or between 5 and 100 nm, or between 5 and 50 nm, or between 5 and 30 nm, or between 5 and 20 nm, or between 50 to 900 nm, or between 100 to 700 nm, or between 200 to 500 nm.

3. The sheet according to claim 1, further comprising at least one additional layer of at least one nano-cellulose material being free of nanoparticles.

4. The sheet according to claim 1, comprising two or more layers of a nanocomposite, or at least 10 layers, or between 10 and 500 layers, or between 10 and 400 layers, or between 10 and 300 layers, or between 10 and 200 layers, between 10 and 100 layers, or between 100 and 500 layers, or between 100 and 400 layers, or between 100 and 300 layers, or between 100 and 200 layers.

5. The sheet according to claim 1, wherein the nanoparticles are quantum dots (QD).

6. The sheet according to claim 1, wherein the substrate material is selected from the group consisting of paper, paperboard, plastic, metal, and composite materials.

7. The sheet according to claim 1, wherein the substrate materials being selected amongst aliphatic polymers optionally selected from the group consisting of polyhydroxyalkanoates (PHA), polylactic acid (PLA), polybutylene succinate (PBS), polycaprolactone (PCL), polyanhydrides, polyvinyl alcohol, starch and starch derivatives and cellulose esters.

8. The sheet according to claim 1, adapted for use in any one or more of the following: a. the manufacture of containers, medical packs, construction materials, wire-coating materials, agricultural materials, food packaging materials and buffer and insulation materials; b. the construction of plastic greenhouses, plastic tunnels, and other agricultural and horticultural articles; and c. improving growth, appearance, disease resistance and desirability of horticultural growths.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 shows Magellan XHR scanning micrographs which display cross section overview of nanoparticle-free NCC film.

(3) FIG. 2 shows a Magellan XHR Scanning micrograph which displays cross section of hybrid a NCC/NP film according to the invention.

(4) FIG. 3 presents a schematic illustration of an embodiment of the invention involving NCC coating on a pre-treated PE sheet using N.sub.2 plasma jet.

(5) FIGS. 4A-B present hybrid PE/NCC sheets on pre-treated N.sub.2 plasma jet sheet (FIG. 4A) or untreated reference sheet (FIG. 4B).

(6) FIG. 5 shows transmission spectra of NCC films mixed with SiO.sub.2 nanocrystals and with CdTe nanocrystals, compared to a bare NCC film. The film which contained the SiO.sub.2 showed some reduction in the transmission at the UV region, as compared to the film containing the CdTe where the absorption at the UV region was sharp.

(7) FIGS. 6A-B: FIG. 6A: transmission spectra of SiO.sub.2 embedded in NCC films at the range of 400-3500 nm. It is visible from the graph that there is a beginning of absorption at the UV range and a decrease in transmission almost to 20% above 2 m. FIG. 6B: transmission spectra of the SiO.sub.2NCC film between 4-16 m. It can be seen that the transmission decrease below 40% above 4 m and above 6 m the light is blocked.

(8) FIG. 7 presents two transmission spectra of the NCC mixed with CdTe nanocrystals. The time lapse in between the measurements is two months. Since without protection the oxidation process occurs within days, the measurements provide a proof that the NCC sheets are indeed oxide barriers.

DETAILED DESCRIPTION OF EMBODIMENTS

(9) Results:

(10) Preparation of Ordered NCC Films with or without NPs.

(11) NCC solutions with or without nanoparticles (NPs) were dried in an oven at 37 C. The resulting films were analyzed using Magellan XHR scanning microscope. The NCC film displayed formation of highly ordered NCC layers having a thickness in the range of 5-20 nm (FIG. 1).

(12) In addition, the hybrid NCC/NP film demonstrated the same ordered layers formation, but with nanoparticles trapped between the layers (FIG. 2).

(13) Preparation of Hybrid Nanomaterials Made of Polyethylene (PE) and NCC

(14) NCC coating on PE sheets was performed using N.sub.2 plasma jet treatment (50% power, 150 W for 5 min, as depicted in FIG. 3). Subsequently, the NCC was spread over the pre-treated PE sheet to form a thin layer. Finally, the PE/NCC sheet was dried in an oven at 37 C. The resulting hybrid sheet displayed uniform NCC coating on the PE sheet, unlike the untreated PE sample, from which the NCC coating was observed to peel off (FIG. 4).

(15) Preparation of Hybrid NCC/Nanocrystals (NC) Films

(16) NCC films were mixed with different NCs to examine their optical properties. The UV blocking was illustrated with core-CdTe 5 nm crystal (FIG. 5). By mixing the NCs with the NCC, followed by drying, a sharp UV cutoff region was demonstrated. In addition, examining 5 nm crystals of SiO.sub.2 mixed into the NCC films exhibited some absorption at the UV range. At the infrared region above 2 the NCC with the SiO.sub.2 NCs showed absorption more pronounced than the NCC alone. FIG. 5 demonstrate that it is possible to change the spectra using sheets of NCC and NCs. Specific NC semiconductors act as an efficient low pass filters, and SiO.sub.2 NCs showed an effect that resembles glass. It is important to note that using CdTe core, only adsorption effects were observed, and not wavelength conversion. With the use of core-shell nanocrystals wavelength conversion was found more efficient.

(17) Further measurements on the NCC/SiO.sub.2: films at longer wavelengths of the mid-far and long IR regions demonstrated improvement of the optical properties of the films as compared to bare NCC films or Polyethylene (FIG. 6). The transmission results displayed absorption (transmission decrease) that started above 2 (2,000 nm), reaching more that 60% above 4 m. Even more important for the Greenhouse effect is the total blocking of the light above 6 m.

(18) Finally, it is demonstrated that the NCC films act as an oxygen barrier. Two subsequent measurements with a two-month gap between them are shown in FIG. 7. The spectra of the CdTe being sensitive to oxidation, does not change with time. In the case of CdTe oxidation, the spectra should be shifted to the UV region. Without the NCC, changes in the spectra are measured within days. It is thus clear that the NCC films provide good protection against the oxidation process.