WO2012138040A1 - Nanodiamond-polymer nanoparticle composite, and a production method therefor - Google Patents

Abstract

The present invention relates to a composite comprising nanodiamond and polymer nanoparticles, and more specifically relates to a composite comprising nanodiamond and polymer nanoparticles whereby re-agglutination of the nanodiamond particles is suppressed while nanodiamond dispersion is markedly improved.

Description

Nanodiamond-polymer nanoparticle composite and thin film thereof

The present invention relates to a composite comprising polymer nanoparticles and nanodiamonds, and more particularly, to a composite including polymer nanoparticles and nanodiamonds, which remarkably improves nanodiamond dispersion while suppressing reaggregation of nanodiamond particles. It is about.

In general, nanomaterials have been applied in various fields. The nanoparticles are supplied as agglomerated powders due to their high surface free energy, and particle dispersity has become an important issue for producing desired polymer nanocomposites.

Among them, diamond nanoparticles have different forms of carbon materials with specific properties and applications. Explosive Particulate Diamond (DND) has been used in comparison to other carbon nanoparticles such as fullerenes, single-walled, double-walled, and multi-walled carbon nanotubes (SWNT, DWNT, and MWNT) and other carbon nanoparticles such as nanofibers. It was discovered relatively early in the Soviet Union (1960s). DNDs received little or no attention until 1988 when two groundbreaking papers appeared in published journals.

Explosive particulate diamond is 2,4,6-trinitrotoluene (TNT) / 1,3,5- under a gas atmosphere, for example in a closed steel chamber in CO ₂ (dry method) or water (wet method). Trinitrotriazacyclohexane (hexogen) was named after being produced by the explosion method.

The nanodiamond material is an amorphous carbon of 1-4 nm diamond crystalline nucleus generated by inducing high temperature and high pressure atmosphere when explosives such as trinitrotoluene (TNT) and white crystalline insoluble bomb RDX (Research department explosive) explode. It is a carbon material with a unique structure that is surrounded by a small particle diameter, a large specific surface area, and has a unique electrical, chemical, and optical characteristics such as including a large number of hydrophilic functional groups on its surface, and the nanodiamonds have superdispersed diamond (UDD) and Two other common names for ultra-nanocrystalline diamond (UNCD) particulates are known, which are 2-10 nm in size (primary nanoparticles) and 200 m ² / g It is because it has a very large specific surface area of the following.

The nanodiamond material exhibits nontoxicity and biocompatibility. This feature provides DND with additional features for biorelevant applications in view of their rich surface chemistry that can be relatively easily modified. Surface functionalities demonstrated by various spectroscopy techniques are mostly oxygenated moieties such as -CO ₂ H (carboxylic acid), lactones, C = O (keto carbonyl), -COC (ether), and -OH (hydroxyl) to be.

Due to these characteristics, research is being conducted in various application fields, and it is widely used in various fields ranging from advanced industrial materials and household goods. In particular, due to its small size, excellent mechanical strength, and unique surface properties that can control its activity, it is highly applicable to polymer fillers as a reinforcing filler.

As such nanodiamonds have important advantages such as mass production (industrial production capacity in Russia, Ukraine, China and Belarus) and moderate price characteristics, DND has attracted great attention as a material platform for nanotechnology.

The nanodiamond material is generally agglomerated strongly with each other when dried due to the nature of the particles, and thus does not exhibit the original particle size and properties, so that a water-soluble liquid product or powder mixed and dispersed in a ratio of 9: 1 with distilled water using a hydrophilic surface property is obtained. It is supplied. Liquid products can be applied directly to aqueous coating solutions, but most polymer resin coating solutions cannot be applied because they use oily solvents. However, the nanodiamond particles during the nanodiamond powder manufacturing process inevitably hardly agglomerated during the purification and drying process, the unit particles are very small as 4 ~ 10 nm, but the powder nanodiamond particles are each larger than the micron size.

Therefore, in the case of powder, it is impossible to apply afterwards without grinding and dispersing in a solvent compatible with the coating solution and improving the hydrophilic surface.

The first problem to be solved by the present invention is to provide a composite comprising a polymer nanoparticles and nanodiamonds.

The second problem to be solved by the present invention is to provide a method for producing a composite comprising the polymer nanoparticles and nanodiamonds.

A third object of the present invention is to provide a thin film including a composite including the polymer nanoparticles and nanodiamonds.

The present invention provides a nanodiamond-polyvinylpyrrolidone nanoparticle composite formed by dispersing nanodiamond (ND) particles and polyvinylpyrrolidone (PVP) nanoparticles.

In addition, the present invention to solve the second technical problem,

1) preparing polyvinylpyrrolidone aqueous solution by stirring the polyvinylpyrrolidone particles; And

2) It provides a method for producing a composite according to the present invention comprising the step of dispersing the nanodiamond particles in the polyvinylpyrrolidone aqueous solution and ultrasonically.

In another aspect, the present invention provides a thin film comprising a composite prepared according to the manufacturing method in order to solve the third technical problem.

According to the composite including the nanoparticles of the polyvinylpyrrolidone nanoparticles or derivatives thereof, which are the polymer nanoparticles according to the present invention, and the nanodiamond particles, the polymer nanoparticles inhibit reaggregation of the nanodiamond particles and at the same time nanodiamonds. The dispersion of particles can be significantly improved, so that the polymeric nanoparticles are effective and economical additives for the dispersion of nanodiamonds. In addition, the nanoparticles of the polyvinylpyrrolidone nanoparticles or derivatives thereof do not affect particle formation even when the concentration is increased. However, when the polymer nanoparticles and the nanodiamond particles are sonicated, the increase in cycle and ultrasonic time induces aggregates, so the presence of the polymer nanoparticles is an important factor for dispersion. In addition, the high specific surface area of the composites according to the invention has the effect of providing good interaction and, as a result, providing excellent mechanical properties of their thin films.

In addition, the thin film produced according to the method for producing a composite according to the present invention exhibits uniform dispersion, reducing the transmittance of UV irradiation and at the same time maintaining the transparency in the visible region.

1 is a graph showing the curve of the correlation between the stirring time and the size of the polyvinylpyrrolidone nanoparticles. After stirring for a predetermined time or more, it can be seen that the size of the polyvinylpyrrolidone nanoparticles is increased again.

Figure 2 is a graph showing the particle size of ND-PVP-NP (0.5% by weight), the total particle size of the nanodiamond particles is 37.5 mm.

3 is a schematic diagram illustrating the rules of polymer nanoparticles in the dispersion process and the dispersibility of aggregated ND using ultrasonic waves in PVP-NP.

Figure 4 (a) is a graph showing the UV-vis spectra of the thin film containing ND-PVP-NP according to the different content of the nanodiamond, (b) is a graph of the ND-PVP-NP according to the different content of nanodiamond A graph showing the UV spectra.

Figure 5 (a) is a graph showing the correlation between the transmittance of the thin film films in the UV region with different degrees of ND loading, (b) is a graph showing the UV-vis spectra of Comparative Example 2.

6 is a diagram showing the protection rate of UV rays of Comparative Example 2-3 and Example 3-4 at 400 nm.

In the present invention, a nanodiamond-polyvinylpyrrolidone nanoparticle composite prepared by dispersing nanodiamond (ND) particles and nanoparticles of polyvinylpyrrolidone (PVP) or a derivative thereof is prepared to solve the problem of agglomeration of nanodiamonds. Overcome

The nanodiamond-polyvinylpyrrolidone nanoparticle composite according to the present invention is characterized by dispersing nanodiamond (ND) particles and nanoparticles of polyvinylpyrrolidone (PVP) or derivatives thereof.

In general, nanodiamonds have a high atomic ratio of nanodiamonds due to their small particle size, which provides defect positions on grain boundaries than natural single diamond crystals or microcrystalline synthetic diamonds. Thus, some of these functional groups such as carboxyl and the like can be grafted with carbon elements on diamond defect sites. That is, some soft aggregates are generated by van der Waals forces between the diamond particles that appear, while some hard aggregates are bound by chemical bonds such as carbonyl or ether groups. Occurred during storage, and especially hard aggregates are more difficult to disperse them individually.

Autologous clusters or first aggregates also form more weakly bound second aggregates in the range of hundreds of nanometers to hundreds of micrometers. In addition, nanodiamond aggregates have a state of dimensional fission figure. Nanodiamond (ND) powder exhibits the unique properties of diamond on nanoscale and is one of the more widely studied nanomaterials. The excellent hardness and thermal conductivity of the diamond core is combined in the ND powder into a highly accessible surface area covered by surface functionalities that are immediately sewn.

In general, the wide bandgap of diamonds (˜5 eV) allows them to be highly adsorbed by UV light, but transparent in the visible and IR range. Thus, NDs are suitable for a wide range of potential applications involving complexes. As a powder, NDs can be introduced in fibers, coatings, or other forms with their useful properties of hardness.

One major obstacle to the production of diamond composites is their ability to deliver them in the form of particles that are well dispersed in the polymer matrix. Conventional polymer manufacturing techniques, such as casting and extrusion, are poorly dispersed due to the aggregation and reaggregation of NDs in the polymer matrix leading to tradeoffs in properties.

In addition, the addition of several percent or more of ND to the polymeric component can substantially increase cost and weight. Thus, preferably ND can be used in certain applications such as surface coatings.

The diamond particles used in the present invention use two types of representative nanodiamonds. That is, there are nanodiamonds (ND5) having an average diameter of about 5 nm and nanodiamonds (ND60) having finely divided microdiamonds. The surface of these nanodiamonds contains amorphous carbon compounds as residues, surrounded by oxygen or hydrogen compounds, and in many cases forms aggregates.

The polyvinylpyrrolidone polymer used in the present invention is composed of a mixture of polyvinylpyrrolidone or polyvinylpyrrolidone derivative, and the nanoparticles of the polyvinylpyrrolidone derivative are poly (1-vinylpyrrolidone- co-vinylacetate), poly (1-vinylpyrrolidone-co-2-dimethylaminoethylmethacrylate).

However, particular preference is given to using polyvinylpyrrolidone, examples of suitable polyvinylpyrrolidone derivatives include copovidone (eg Kollidon VA 64, manufactured by BASF). It is a 6: 4 copolymer of vinylpyrrolidone and vinyl acetate.

The weight average molecular weight of the polyvinylpyrrolidone is preferably 250 g / mol to 360 kg / mol. Outside of the above range, the chain structure of the polymer material becomes difficult to unwind and it is difficult to form nanoparticles. .

The polyvinylpyrrolidone (povidone, PVP) is a commercially available hydrophilic polymer suitable for use in delayed release solid pharmaceutical formulations. Various kinds of PVP are commercially available. Relatively low molecular weight PVP is usually used as a tablet binder. PVP expands and disintegrates in aqueous media. However, PVP-containing tablets have not been shown to form sticky gel layers, such as, for example, cellulose ethers. According to the in vitro experiments of the present invention, PVP-containing tablets do not exhibit tack even in an aqueous medium. The risk of aggregation in the gastrointestinal tract is low when administering multiple tablets. By using PVPs having different molecular weights, the release kinetics can be varied within a defined range.

The nanodiamond-polyvinylpyrrolidone nanoparticle complexes according to the present invention were generated during an ultrasonic process in the presence of PVP-NP nanoparticles that cause cavitation cracks, and simultaneously coagulated and core aggregated nanodiamond particles. Loose in the weak part of Polymer nanoparticles inserted between loosely agglomerated nanodiamond particles were divided into very small particles, segregated and partially encapsulated on nanodiamonds, between nanodiamond aggregates to disperse them for very small nanodiamond particles. Means insertion of PVP-NP.

The weight ratio of the nanodiamond (ND) particles and the nanoparticles of polyvinylpyrrolidone (PVP) or derivatives thereof used in the present invention is 4:96 ~ 45:55, it is out of the range of the nanodiamond It is not preferable because the content is too small and has a disadvantage in that the UV transmittance is very high when manufacturing a thin film, or it is not preferable because the dispersion may not be performed properly because it is excessive.

The nanodiamond-polyvinylpyrrolidone nanoparticle composite of the present invention may include a conventional additive in a usual amount of use.

In general, nanodiamond powder can hinder the potential application of ND if its aggregates are not broken. There are many methods already used to distribute ND. However, stronger conditions are used, for example, high peripheral speeds and long milling times, and high contents of zirconia are detected.

However, zirconia can be removed by strong acid treatment which can be carefully applied due to the accompanying chemical reaction. It has also been found that high power ultrasound is an efficient technique for breaking adhesion.

Ultrasound alone, on the other hand, was unable to achieve the first particles of NDs, and the presence of beads significantly changed the results.

However, when attempting to replace milling with high power sonication in the presence of zirconia beads, post-ultrasound is not necessary in the process and is labeled as "bead-assisted sonic decay (BASD)". It is a functionalized method for dispersion and is mostly based on chemical grafting of alkyl chains through chemical functionalization, esterification or silylation reactions.

In general, these chemical reactions require entirely hours and their chemical conditions, and the process is complex. In addition, physical techniques are used by mixing suitable dispersants in powder suspensions, which are then separated by application of sonication.

However, suitable dispersants and mechanical techniques of bead-milling should be used to obtain clean colloids of NDs.

Spherical polymeric nanoparticles are of great interest in their application as templates for drug delivery systems, photonic crystal applications and other periodic structures with nanometer ranges for micrometer sizes.

The present invention uses polymer nanoparticles prepared by magnetic stirring to disperse NDs. First, polyvinylpyrrolidone polymer nanoparticles were prepared using a dispersion method, which readily prepared polymer nanoparticles of different sizes of polyvinylpyrrolidone, and mixed them into ND powder using ultrasonic waves.

That is, the composite of nanodiamonds and polyvinylpyrrolidone nanoparticles according to the present invention may have different particle sizes depending on the dispersion of aggregated nanodiamonds using ultrasonic technology.

Method for producing a nanodiamond-polyvinylpyrrolidone nanoparticle composite according to the present invention

1) preparing polyvinylpyrrolidone or a derivative thereof in a solvent and stirring to prepare a solution containing nanoparticles of polyvinylpyrrolidone or a derivative thereof; And

2) characterized in that it comprises the step of dispersing ultrasonically by putting the nanodiamond particles in a solution containing nanoparticles of the polyvinylpyrrolidone or derivatives thereof.

In the present invention, step 1) is performed by dissolving polyvinylpyrrolidone or a derivative thereof in ionized water and mechanically stirring the mixture at 0-35 ° C. for 30 minutes to 24 hours to determine the polyvinylpyrrolidone or derivative thereof. It is not preferable to obtain an aqueous solution of nanoparticles, but less than 30 minutes, since the size of the PVP-nanoparticles may be such that the effect of the present invention can not be achieved, and the size of the smaller particles may increase again after 24 hours. Not desirable

In the present invention, in step 2), the nanodiamond particles are added to a solution containing the nanoparticles of the polyvinylpyrrolidone or a derivative thereof, and the dispersion is performed by ultrasonic waves for 15 minutes to 1 hour.

The weight ratio of the nanodiamonds (ND) particles used in the present invention and the nanoparticles of polyvinylpyrrolidone (PVP) or derivatives thereof is 4:96 to 45:55.

The nanodiamond-polyvinylpyrrolidone nanoparticle composite according to the present invention may be used as a raw material for producing a composite such as glass, plastic, synthetic fiber, ceramic, or the like, or as an additive to toothpaste, shampoo, soap, cosmetics, and the like.

The thin film of the nanodiamond-polyvinylpyrrolidone nanoparticle composite according to the present invention is characterized in that it comprises the nanodiamond-polyvinylpyrrolidone nanoparticle composite.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention should not be construed as being limited to these examples.

Examples and Comparative Examples

<Measurement of Properties>

1. The thickness of the thin film was measured using a surface roughness measuring instrument (Surfcorder ET3000i / 3000F, Kosaka Laboratory Ltd.).

Production Example

First, polyvinylpyrrolidone (PVP) (made by Merck) was prepared by using the method of stirring at room temperature. 5 mg of polyvinylpyrrolidone was added to 1 ml of deionized water and stirred at room temperature for 5 hours to obtain an aqueous polyvinylpyrrolidone nanoparticle solution (PVP-NP).

The dispersion state of the polyvinylpyrrolidone nanoparticles in the aqueous solution was confirmed by microscopic techniques, and the polyvinylpyrrolidone nanoparticles (PVP-NP) were not produced without stirring, so only polyvinylpyrrolidone was present, and 30 minutes When stirred for a while, a very large size dispersion was formed, and the stirring time to increase the nanoparticles reduced the particle size with a very narrow size dispersion.

Referring to FIG. 1, the size of PVP-NP decreased with increasing agitation time to a minimum point, and increased again after a certain time.

Example 1

5 mg of nanodiamond particles (Nanodiamond PL-D-G01, average size: 4 nm) were included in 4 ml of PVP-NP aqueous solution obtained in the above preparation, and the nanodiamonds were dispersed by ultrasonic wave for 20 minutes, followed by 2500 rpm. Centrifugation was performed for 30 minutes at, and the supernatant was slowly poured into distilled water, stirred well, and filtered using a membrane filter. The product was dried in an oven at 80 ° C. for 4 hours to prepare a composite.

Example 2

It was prepared in the same manner as in Example 1 except that 13.3 mg of nanodiamond particles were used.

Example 3

In order to prepare a thin film containing the composite, the thin film containing the composite obtained in Example 1 was prepared by a known method, and then dried.

Example 4

Except for using the composite obtained in Example 2 was prepared in the same manner as in Example 3.

Comparative Example 1

5 mg of nanodiamond particles without PVP-NP were prepared in the same manner as in Example 1 except that 5 ml of water was dispersed in 5 ml of water for 20 minutes, but agglomeration of diamonds occurred.

Comparative Example 2

5 mg of nanodiamond particles were contained in 5 ml of aqueous polyvinylpyrrolidone solution (PVP-NP) prepared without stirring by adding 25 mg of polyvinylpyrrolidone to 5 ml of deionized water for 20 minutes by ultrasound. After the diamond was dispersed, centrifugation was performed and the supernatant was slowly poured into distilled water, stirred well, and filtered using a membrane filter. The product was dried in an oven at 80 ° C. for 4 hours to prepare a composite. Then, a thin film including the composite was prepared in the same manner as in Example 3, and then dried.

Comparative Example 3

2 mg of nanodiamond particles were contained in 4 ml of the PVP-NP aqueous solution obtained in the above preparation, and the nanodiamonds were dispersed by ultrasound for 5 hours, followed by centrifugation, and the supernatant was slowly poured into distilled water and stirred well. It was filtered using a filter. The product was dried in an oven at 80 ° C. for 4 hours to prepare a composite. A thin film including the composite was prepared in the same manner as in Example 3, and then dried.

It can be seen that nanodiamonds were dispersed into very small particles due to the stronger interaction between polyvinylpyrrolidone nanoparticles and nanodiamond particles, and the specific surface area increased the induction of increased contact therebetween. The interaction between nanodiamonds and PVP-NP is more apparent here.

In general, UV-sensitive materials can be effectively protected from UV rays on windows. This is significant because it is the first case using polymer nanoparticles to disperse NDs.

Ultraviolet rays severely damage human and natural and synthetic materials, including wood and plastic paints.

For thin films with different amounts of nanodiamond particles, the use of polymeric nanoparticle methods for the dispersion of nanodiamond particles in the composite was studied.

These thin films are transparent in the visible region and absorbed in the UV region. Thus, it effectively protects against erosion of UV radiation or UV sensitive materials on windows.

In addition, these thin films of ND-PVP-NP provided a scratch-resistant coating depending on the mechanical, thermal, insulator properties and the presence of nanodiamonds that could be used on the surface with UV protection.

UV irradiation from the sun (UVR) was divided into three areas: UVC (270-290 nm), UVB (290-320 nm), and UVA (320-400), UVC emitted from the sun was filtered by ozone under the atmosphere, Therefore, it does not reach the earth's surface.

The following UV irradiation is therefore concerned with human health: UVB (290-320 nm) and UVA (320-400 nm)

The spectroscopy characteristic experiment of Example 3-4 was performed. The thin films of Examples 3-4 had the same thickness of 500 ± 50 nm.

The transmittance of UV irradiation decreased with increasing contents of 20% by weight and 40% by weight of diamond particles of Examples 3-4.

Some absorption in the visible region is due to the presence of sp ² carbon on the surface of the nanodiamonds.

As shown in Figures 4 and 5, Examples 3 and 4 have a low transmittance of UV irradiation, whereas in Comparative Examples 2 and 3 it can be seen that the transmittance of UV irradiation is very high.

Referring to Figure 6 it can be seen that Examples 3 and 4 are very high UV-protection rate of 70-75% compared to Comparative Examples 2 and 3. This shows the relationship between the UV radiation and the transparency of the ND content.

The presence of the polyvinylpyrrolidone particles aids in the dispersibility of the nanodiamond particles, particularly in the high content of nanodiamonds in the polyvinylpyrrolidone-diamond composite according to the present invention, and the diamond in a form that is more uniformly dispersed throughout the thin film. Nanoparticles were delivered and covered the entire area.

The polyvinylpyrrolidone particles used in the composite according to the present invention play a pivotal role in dispersion and reflect within UV absorption as described above.

Therefore, as shown in FIG. 6, Examples 3 and 4 in which nanodiamond particles and polyvinylpyrrolidone particles are well dispersed have UV protection at 400 nm or higher, whereas Comparative Examples 2 and 3 are 50. Very low, below%.

Thus, in the case of Comparative Examples 2 and 3, the diamond was more aggregated and not uniformly dispersed in the thin film, so as shown in Figs. 5 and 6, the transmittance was very high compared to Examples 3 and 4, and the protection of UV rays The rates are very low at 46.5% and 49.5%.

Notably, these thin films have the advantage of being optically transparent in the visible region. The above can have an application potential in many areas, such as glass coatings and protective layers, on UV-sensitive materials.

The approach using polymeric nanoparticles for the dispersion of nanodiamond particles is very easy, effective and economical.

Thus, the thin film according to the present invention can deliver nanodiamond particles in a more dispersed form for their use in other applications by heating to completely remove the polymer to obtain a pure nanodiamond coating, and the chemistry of the polycrystalline diamond film Seeds for vapor deposition (CVD) may be provided.

The method for dispersing nanodiamonds can be extended to many different types of polymers and improve their mechanical properties.

Claims (9)

1. A nanodiamond-polyvinylpyrrolidone nanoparticle composite, comprising: dispersing nanodiamond (ND) particles and nanoparticles of polyvinylpyrrolidone (PVP) or a derivative thereof.
2. The method of claim 1, wherein the polyvinylpyrrolidone derivative is selected from poly (1-vinylpyrrolidone-co-vinylacetate), poly (1-vinylpyrrolidone-co-2-dimethylaminoethyl methacrylate). Nanodiamond-polyvinylpyrrolidone nanoparticle composite, characterized in that it is selected from one or more mixtures selected.
3. According to claim 1, wherein the weight ratio of the nanodiamond (ND) particles and the nanoparticles of polyvinylpyrrolidone (PVP) or derivatives thereof is 4:96 ~ 45:55 nanodiamond-polyvinylpyrroly Don nanoparticle complex.
4. A composite of nanodiamonds and polyvinylpyrrolidone nanoparticles, wherein the nanoparticles of the granulated polyvinylpyrrolidone or a derivative thereof are dispersed and uniformly distributed.
5. 1) preparing polyvinylpyrrolidone or a derivative thereof in a solvent and stirring to prepare a solution containing nanoparticles of polyvinylpyrrolidone or a derivative thereof; And

   2) Method of producing a nanodiamond-polyvinylpyrrolidone nanoparticles composite, comprising the step of dispersing the nanodiamond particles in a solution containing the nanoparticles of the polyvinylpyrrolidone or derivatives thereof by ultrasonic wave .
6. The method of claim 5, further comprising: in the step 1), determining a stirring time for minimizing the size of the nanoparticles of the polyvinylpyrrolidone or derivatives thereof.

   In step 2), the nanodiamond-poly, characterized in that further comprising the step of determining the dispersion time of the ultrasonic wave in which the nanodiamond particles are dispersed as much as possible in the solution containing the nanoparticles of polyvinylpyrrolidone or derivatives thereof Method for producing vinylpyrrolidone nanoparticle composite.
7. The method of claim 5, wherein the step 1) is nanodiamond-polyvinylpyrroly characterized in that the polyvinylpyrrolidone or a derivative thereof is dissolved in water and stirred at 0-35 ° C. for 30 minutes to 24 hours. Method for producing a don nanoparticle composite.
8. The method of claim 5, wherein the step 2) comprises nanodiamond particles in a solution containing nanoparticles of the polyvinylpyrrolidone or derivatives thereof, and dispersing with ultrasonic waves for 15 minutes to 1 hour. Method for preparing diamond-polyvinylpyrrolidone nanoparticle composite.
9. A thin film comprising the nanodiamond-polyvinylpyrrolidone nanoparticle composite according to any one of claims 1 to 4.

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