WO2017191370A1

WO2017191370A1 - Method for co-depositing detonation nanodiamonds and diamond-like carbon onto a substrate and composite films comprising detonation nanodiamonds and diamond-like carbon

Info

Publication number: WO2017191370A1
Application number: PCT/FI2017/050350
Authority: WO
Inventors: Jarkko ETULA; Ajai IYER; Jari Koskinen
Original assignee: Aalto University Foundation Sr.
Priority date: 2016-05-06
Filing date: 2017-05-05
Publication date: 2017-11-09
Also published as: CN109563612A; KR20190023050A; EP3452630A1

Abstract

The present application provides a method for co-depositing nanodiamonds and diamond-like carbon onto a substrate with physical vapor deposition (PVD) method, the method comprising providing a substrate, providing a source of ionized carbon plasma, providing a source of nanodiamonds, ejecting the nanodiamonds and the ionized carbon plasma towards the substrate to co-deposit the nanodiamonds and diamond-like carbon onto the substrate. The present application also provides a composite film comprising nanodiamonds and diamond-like carbon.

Description

Method for co-depositing detonation nanodiamonds and diamond-like carbon onto a substrate and composite films comprising detonation nanodiamonds and diamond-like carbon Field of the application

The present application relates to methods for co-depositing nanodiamonds and diamond-like carbon onto a substrate with physical vapor deposition (PVD) method. The present application also relates to composite films comprising nanodiamonds and diamond-like carbon obtained with said methods.

Background

Nanodiamonds (NDs) have found wide fields of application due to their versatile properties due to the presence of stable diamond core. However, growth of nanodiamonds on any surface is generally done by chemical vapor deposition (CVD) at high temperatures. In many cases such high temperature processes cannot be performed due to substrate considerations and in cases where the NDs need to be embedded. Thus it is easier to proceed from pre-made NDs which are synthesized by a detonation process. Detonation nanodiamonds (DNDs) have a diamond core surrounded by sp² carbon shell which allows for a variety of applications. It has been shown that incorporation of DNDs in an epoxy matrix can improve the mechanical properties of the epoxy. In a similar fashion incorporation of DNDs in metal matrix can improve the mechanical properties of the metal, specifically the hardness. However making any hard thin film coating with DNDs alone is not possible, without embedding them in a matrix material.

Diamond like Carbon (DLC) is an amorphous carbon coating which is very hard and used as a mechanical coating at an industrial scale, such as tetrahedral amorphous carbon (ta-C). DLC/ta-C films with embedded NDs have been fabricated either by depositing the NDs before DLC/ta-C film growth or by CVD methods at high temperature, where process parameters must be varied to cater to nucleation of NDs and DLC separately. No or very few alternative low temperature methods for diamond/carbon composite materials are available which restrict the application of the films and limits the use of substrate materials. If carbon thin films are functional ized by using nano particles which are relatively weakly bonded to the carbon film surface, this results in possibly unwanted nano particle emission in the course of usage. Certain applications require films with hardness better than ta-C. The only possible solution is growth of diamond films which are primarily expensive and have the problem of special substrate preparation for good adhesion.

Also improper embedding of nano-particles might lead to changes in nanoparticle properties such as optical, electrochemical and magnetic.

Brief description

The present application provides a method for co-depositing nanodiamonds and diamond-like carbon onto a substrate with physical vapor deposition (PVD) method, the method comprising

-providing a substrate,

-providing a source of ionized carbon plasma,

-providing a source of nanodiamonds,

-ejecting the nanodiamonds and the ionized carbon plasma towards the substrate to co-deposit the detonation nanodiamonds and diamond-like carbon onto the substrate.

The present application also provides a composite film comprising nanodiamonds and diamond-like carbon.

Diamond like Carbon (DLC) films provide high hardness and wear protective properties. Detonation Nanodiamonds (DNDs) have high sp³ content, small size (few nanometers) and many other interesting properties. Diverse methods have been used to grow nano and ultra nano crystalline diamond films for various applications. The present disclosure provides a method wherein DLC and DNDs are co-deposited from the same cathode by a physical vapor deposition (PVD) method. Transmission Electron Microscope (TEM) analysis of these films reveal the presence of nanodiamonds embedded in a matrix of amorphous carbon. Raman spectroscopy indicates that the DND-DLC composite film is of similar quality as DLC film of same thickness. Nanoindentation and nanowear tests on DND-DLC composite films show better performance when compared to DLC films of similar thickness. The present disclosure provides embodiments where DND-embedded DLC can be fabricated by a one step process using PVD techniques at room temperature. The process involves co-deposition of DNDs and DLC from the same target or source to form a composite thin film on substrate. By this process it is possible to control the sp³/sp² ratio of the DLC film, the quantity of DNDs in the film and also make multilayers or gradient layers. The multilayer may comprise alternate layers of DLC and DND embedded DLC to get enhanced wear properties at certain depths or for optical applications. The gradient layer may comprise changes in concentration of DNDs as a function of thickness of the layer. In essence, the carbon target or source is loaded with DNDs some of which are ejected in the deposition process. The deposition may be performed by standard PVD methods including, but not limited to, DC Magnetron Sputtering, RF Magnetron Sputtering, Cathodic Arc (DC or pulsed, which may be filtered or un-filtered) and Ion beam assisted deposition. Here the proof of concept of the method of co-depositing DNDs and DLC from the same cathode using a pulsed filtered cathodic vacuum arc process (p-FCVA) at ambient temperature is presented. The ejected DNDs travel in the ionized carbon plasma stream and are not filtered if they are few tens to few hundreds of nanometers in size. On the substrate, the DNDs are embedded in the growing DLC film forming a nano-composite film by a one-step deposition process operating at room temperature. Deposited films were characterized by TEM, SEM, Raman spectroscopy and Nano-indentation.

It was shown in tests that the FCVA process yields the best form of DLC, namely tetrahedral amorphous carbon (ta-C). Tetrahedral amorphous carbon is the hardest DLC coating type, having a hardness value of in the range of about 25-50 Gpa. The present process yields DND-ta-C films. There is no restriction of the substrate in this process from temperature standpoint. The only restriction comes from adhesion of the films to the substrate. Thus substrates may be for example silicon, glass, plastic/polymer foils, metals and oxides (alumina/titania).

These DND-ta-C films have improved hardness and wear properties compared to ta-C films. In addition, tests indicate that DND-ta-C films are very sensitive to bio- molecule detection as well. Additionally, the ND functional ization may be varied to get different sensitivity for different bio-molecules. The thin films obtained with the methods described herein may be applied for example as mechanical coating, electrical applications, optical applications, biomaterials, implants, sensors such as biosensors or biomolecular sensors . Mechanical coating is obtained which is extremely hard, especially harder than ta- C coating. The coating may obviate the need for diamond coatings in some cases. Examples of the coatings include tool and tribological coatings, such as tribologically favourable coatings for gears and shafts. The ND-ta-C coating may be used as mechanical coatings for tool and die coating. The process can be used in existing PVD systems with minimum alteration.

The obtained films are continuous and non-breaking and exhibit good adhesion to substrates. In many cases it was possible to obtain films which are flexible and elastic, for example providing extension of up to 15%.

It was observed that ND-ta-C films are electrochemically active with the benefit of both, molecular selectivity offered by the functionalized NDs and low background current (high dielectric nature) due to ta-C. Electrical applications include for example electrochemical applications, such as thin film sensors. With a suitable functionalization of the nanodiamonds an array based lab on chip may be obtained. The electrochemical behavior was studied.

In addition, NDs have interesting optical properties. Such a thin film of ND-ta-C is photo-active under favourable conditions and may be used in applications in solar cells. There has been a large volume of work done on depositing NDs on and in optical fibers for a variety of applications including waveguide applications, photon sources and optical sensor applications. With the present ND-ta-C coatings, photonic crystal fibers may be coated inside as well as outside with NDs in a much easier method to achieve some of the above mentioned objectives.

Optical applications include waveguides and the like optical and fiber optic applications. It is possible to coat photonic crystal fibers with ND-ta-C film enhancing waveguiding modes, optical wavelength selection, wavelength conversion and other aspects. The ND-ta-C film may itself be used as optical waveguide on chip. Examples include applications for wavelength changes, soliton production, sensing and waveguiding applications. With high enough concentrations of nanodiamonds (in the ND-ta-C film) the film itself may show interesting optical properties and then may be fashioned by lithography to make optical micro-waveguides on chip.

Biomaterial applications include for example biomaterial substrates. Cells difficult to grow on other substrates (such as neurons) may grow favorably on ND-ta-C films.

Sensor applications include for example biosensors and biomolecular sensors. Tests indicate that ND-ta-C films may be used as bio-sensors for detecting target bio-molecules with very low concentration and high accuracy. ND-ta-C films are ideal bio-sensor films with the added advantage of being mechanically rugged and hard. Examples of sensing targets include neural sensing, blood, pharmaceutical drugs, narcotics etc. Benefits for bio-sensors are in using the films as arrays for sensing bio-molecules. The possibility of functionalizing the NDs allows binding of different bio-molecules allowing for an array based lab on chip which could quickly and efficiently detect a variety of bio-molecules.

The possibility of making ND-ta-C coatings at room temperature allows use of almost any substrate (subject to adhesion). Any other traditional processes (Mostly CVD or ALD) able to make diamond/DLC composite run at elevated temperatures, thus reducing the substrates allowed.

The feature of having the NDs embedded in ta-C matrix and control over depth distribution is not possible by traditional processes.

The methods of the embodiments enable manufacturing composite films in industrial scale, which is not possible with many conventional methods. More particularly, films with large volumes, areas and/or surfaces can be manufactured, and the process is scalable.

Brief description of the figures

Figure 1 shows SEM cross-section images of 50 nm thick DND-DLC film: (a) Low magnification image of substrate and film interface; (b) High Magnification image of substrate and film interface. Figure 2 shows TEM analysis of 0.05 wt% DND on TEM grid: (a) HR-TEM image where DNDs are clearly visible; (b) Diffraction pattern with the d-spacing marked. Figure 3 shows TEM analysis of DND-DLC film on TEM grid: (a) HR-TEM image where DNDs embedded in amorphous DLC film are visible (marked by white ellipses); (b) Diffraction pattern from DND-DLC film with the d-spacing marked. Figure 4 shows Raman spectra acquired at 488 nm wavelength: (a) Reference ta-C 50 nm thick; (b) DND-ta-C 50 nm thick.

Figure 5 shows Nano-indentation and nano-wear plots: (a) 12 point nano- indentation for reference ta-C and DND-ta-C calculated with pre and post calibrated area functions; (b) Wear volume ratio for reference ta-C and DND-ta-C as a function of load plotted for 4 scan passes.

Figure 6 shows a diagram of an example of a ND-taC co-deposition method using cathodic arc

Figure 7 shows another point and analysis of the samples disclosed in Figures 2 and 3. Figure 7 (a) and (b) shows TEM analysis of 0.05 wt% DND on TEM grid: (a) HR-TEM image where DNDs are clearly visible; (b) Diffraction pattern with the d-spacing marked; Figure 7 (c) and (d) shows TEM analysis of DND-DLC film on TEM grid: (c) HR-TEM image where DNDs embedded in amorphous DLC film are visible (marked by arrows); (d) Diffraction pattern from DND-DLC film with the d- spacing marked; Figure (e) is data analysis (FFT) performed on selected area of Fig 7 (c) to show cubic diamond; Figure 7 (f) is DND size distribution analysis in the composite film.

Detailed description

Diamond-like carbon (DLC) is a metastable form of amorphous carbon with significant sp³ bonding. DLC is a semiconductor with high mechanical hardness, elastic modulus, chemical inertness, and optical transparency. The features of DLC are explained in detail in J. Robertson, "Diamond like amorphous carbon", Mat. Sci. Eng. R 37, 129 (2002) which is incorporated herein by reference. A low temperature method to deposit ND-ta-C coatings with excellent properties is introduced, enabling hardness, wear resistance, electro chemical sensing applications, and further chemical functionalization of nanodiamonds in the composite film. The coatings provide solutions e.g. for engineering, sensors, bio- sensors and bio-materials.

One embodiment utilizes FCVA which was shown to yield superior quality ta-C. In addition by embedding nanodiamond particles in the graphitic target (cathode of the arc discharge) for FCVA the nanodiamonds are propelled by the plasma and form embedded coating with ta-C. This process is purely room temperature on the macro scale with no requirement of substrate heating or cooling. In addition the nanodiamonds are strongly embedded in the matrix of ta-C while retaining all the desired qualities of nanoparticles. Hence in the course of usage as thin films there is no unwanted nanoparticle emission.

The nanodiamond embedded ta-C layer has higher hardness than ta-C itself possibly due to existence of dense sp³ clusters from the nanodiamonds which promotes sp³ formation. The natural layering of nanodiamond in the course of deposition with higher concentrations of nanodiamonds in the beginning, i.e. closer to substrate, offers the thin film with unique inverse wear rate. The wear rate tends to reduce with increasing wear depth due to presence of more nanodiamonds in the composite as depth increases. It was shown that presence of nanodiamonds reduces friction coefficient especially in the presence of lubricant (even water works). Hence ND-ta-C films have lower frictional coefficient compared to bare ta- C films and as wear increases, thus exposing more nanodiamonds, the frictional coefficient would decrease even more.

The present disclosure provides a method for co-depositing nanodiamonds and diamond-like carbon onto a substrate with physical vapor deposition (PVD) method. Physical vapor deposition methods include a variety of vacuum deposition methods which can be used to produce thin films and coatings. In a PVD process the material goes from a solid phase to a vapor phase and then back to a thin film solid phase. Examples of PVD methods include cathodic arc deposition, electron beam physical vapor deposition, evaporative deposition, pulsed laser deposition, sputter deposition and sublimation sandwich method. Methods using too high energies are not preferred herein for depositing nanodiamonds, such as laser ablation methods or electron beam physical vapor deposition methods, as they may damage or destroy the nanodiamonds. Sputtering method may be used, especially for deposition of diamond-like carbon, such as DC or RF sputtering of a graphite electrode by Ar plasma. In ion beam sputtering a beam of Ar ions can be used to sputter from the graphite target to create carbon flux. A second Ar ion beam can be used to bombard the growing film to densify the film or encourage sp³ bonding. In one embodiment the physical vapor deposition method is DC Magnetron Sputtering method. In one embodiment the physical vapor deposition method is RF Magnetron Sputtering method. In ion beam deposition the DLC film is condensed from a beam containing medium energy, such as about 100 eV, carbon or hydrocarbon ions. It is the impact of these ions on the growing film that includes the sp³ bonding, a physical process. In one embodiment the physical vapor deposition method is ion beam assisted deposition method.

In a cathodic arc method an arc may be initiated in a high vacuum by touching a graphite cathode with a small carbon striker electrode and withdrawing the striker. This produces energetic plasma with a high ion density of up to 10¹³ cm³. The power supply may be a low voltage, high currency supply. The cathode spot is small, approximately 1-10 μιτι, and it carries a very high current density of 10⁶— 10⁸ A cm^"2. The spot is formed by an explosive emission process, which creates particulates as well as the desired plasma. The particulates can be filtered by passing the plasma along a toroidal magnetic filter duct. This is called as filtered cathodic vacuum arc (FCVA). The toroidal currents produce a magnetic field of about 0.1 T along the axis of the filter. The electrons of the plasma spiral around the magnetic field lines and so they follow them along the filter axis. This motion produces an electrostatic field, which causes the positive ions to follow the electrons around the filter. This produces an amipolar transport of the plasma around the filter. The particulates cannot follow the field and they hit the walls and baffles on the walls. Alternatively, in the open filter system, the particulates pass between the coils out of the filter zone into the chamber. The neutrals also hit the walls, so the filter raises the plasma ionization from about 30% to nearly 100% at the filter exit. The plasma beam is condensed onto a substrate to produce the ta- C. At the cathode end, the plasma has a mean ion energy of 10-60 eV, depending on the arc current and it has a Gaussian distribution of ion energies. A DC or RF self-bias voltage applied to the substrate may be used to increase the incident ion energy. The FCVA should be operated at a background pressure of about 10^"8 Torr, but this may rise to 10^"5 when the plasma is running. The advantages of the FCVA are that it produces highly ionized plasma with an energetic species, a fairly narrow ion energy distribution, and high growth rates of 1 nm s^"1 for a low capital cost. It can be used on an industrial scale. Unlike ion beam deposition, the depositing beam in FCVA is a neutral plasma beam so that it can deposit onto insulating substrates.

The arc can run continuously or in a pulsed mode. The pulsed mode occurs by using a capacitor bank to strike the arc, or by laser initiation. The arc current can be passed through the filter coils. The pulsed mode allows better filtering, because the ions tend to be entrained in the plasma beam during the pulse, but fall out of the plasma when the beam stops.

In a preferred embodiment the process is carried out by using a cathodic arc method. In one embodiment the physical vapor deposition method is cathodic arc method and the source of ionized carbon plasma comprises a solid cathode. The solid cathode may be graphite cathode, such as graphite rod or the like.

In one embodiment the cathodic arc method is un-filtered cathodic arc method. In one embodiment the cathodic arc method is filtered cathodic arc method. In one embodiment the cathodic arc method is pulsed cathodic arc method, such as cathodic vacuum arc method.

In general the method comprises

-providing a substrate,

-providing a source of ionized carbon plasma,

-providing a source of nanodiamonds, and

-ejecting the nanodiamonds and the ionized carbon plasma towards the substrate to co-deposit the nanodiamonds and diamond-like carbon onto the substrate. The codeposit formed on the substrate may be called as a film or a coating, which terms may be used interchangeably. If the codeposit is removed from the substrate, it is called as a film.

The substrate may be any suitable substrate onto which the nanodiamonds and the diamond-like-carbon may be co-deposited. The substrate may be selected from silicon, glass, organic polymers, such as plastic, and metals and oxides thereof, such as alumina or titania. The organic polymers may be thermoplastic polymers, such as acrylic polymers, acrylonitrile butadiene styrene (ABS), Nylon, polylactic acid, polybenzimidazole, polycarbonate, polyether sulfone, polyetherether ketone, polyetherimide, polyethylene, polypropylene oxide, polyphenylene sulfide, polypropylene, polystyrene, polyvinyl chloride, or polytetrafluoroethylene (PTFE).

The metals may be any suitable metals or alloys thereof, such as iron, nickel, copper, silver, platinum, gold, aluminium, tin, titanium, and alloys thereof such as steel.

In one embodiment the source of ionized carbon plasma comprises solid carbon, such as a solid carbon electrode. In one embodiment the solid carbon comprises solid graphite. The graphite may be provided as a solid piece, such as a rod, a plate, a cube, and the like. The carbon source should be as pure carbon as possible. Especially the carbon source should not contain boron compounds, nitrogen compounds, fluoride compounds, or (earth) alkaline metals

The nanodiamonds are provided as ready-made or pre-made nanodiamonds. They are not prepared in the present methods. In one embodiment the mean average diameter of the nanodiamonds is in the range of 1-25 nm, such as 3-10 nm.

In one embodiment the nanodiamonds comprise detonation nanodiamonds, or they are detonation nanodiamonds. Detonation nanodiamonds, which are also known as ultradispersed diamonds, are diamonds that originates from a detonation. For example an oxygen-deficient explosive mixture of TNT/RDX may be detonated in a closed chamber, wherein diamond particles with a diameter of approximately 5 nm are formed at the front of the detonation wave in the span of several microseconds. The detonation nanodiamonds may be present as agglomerates of single diamonds. In one embodiment the detonation nanodiamonds are present as agglomerates having mean average diameter in the range of 3-100 nm.

Diamond nanocrystals can also be synthesized from a suspension of graphite in organic liquid at atmospheric pressure and room temperature using ultrasonic cavitation. An alternative synthesis technique is irradiation of graphite by high- energy laser pulses. The structure and particle size of the obtained diamond is rather similar to that obtained in explosion. The nanodiamonds and the carbon, more particularly as ionized carbon plasma, may be provided as different or separate sources or they may be provided as one and same source. More particularly the nanodiamonds and the carbon may be deposited from different or separate sources or they may be deposited from the same source. The carbon from the carbon source, which is the source of ionized carbon plasma, will deposit as the diamond-like carbon onto the substrate.

In one embodiment the nanodiamonds and the diamond-like carbon are provided or deposited from different sources. The ionized carbon plasma may be provided with the cathodic arc method, or it may be provided from a solid carbon to which energy is provided, for example with a sputtering method or with an ion beam assisted method, to obtain an ionized carbon plasma stream. The nanodiamonds are provided from another source, which is generally at a different location than the carbon source. This source may be for example an Ar ion source, such as DC or RF Magnetron, or ultrasonic dispensor and the nanodiamonds may be ejected by the Ar plasma or scattered into the chamber due to the high frequency ultrasonic agitation of nanodiamond powder. In one embodiment the nanodiamonds and the diamond-like carbon are deposited from the same source, such as from the same electrode, such as cathode. In such case the carbon source may contain one or more aperture(s), cavity/cavities, or hole(s), for example cylindrical or hemispherical, for receiving the nanodiamonds. Any suitable geometry of the electrode and/or the apertures may be used. For example a carbon rod, such as a graphite rod, may be provided having such apertures at one end, as shown in Figure 6. The diameter of a carbon rod may be for example in the range of 5-15 mm, such as 5-10 mm. At one end of the rod there may be one or more apertures, such as a plurality of apertures, for example 2-10 apertures, which may have a depth in the range of 0.5-10 mm, such as 3-10 mm, wherein the nanodiamonds may be applied.

In one embodiment the method comprises

-providing a solid graphite cathode comprising one or more aperture(s) for receiving nanodiamonds,

-applying the nanodiamonds to the one or more apertures in the cathode,

-forming an arc with the cathode to provide a source of ionized carbon plasma and to eject the nanodiamonds and the ionized carbon plasma from the cathode to co- deposit the nanodiamonds and diamond-like carbon onto the substrate. In one embodiment the nanodiamonds are provided in a solution. The solution may be an aqueous solution, or it may be a solution of one or more organic solvent(s), such as alcohol, for example methanol, ethanol, propanol, isopropanol and the like, or acetone, or the like. The nanodiamonds form a colloid in any evaporable medium. Preferably the solvent can be evaporated i.e. the solvent is evaporable, for example by using heat.

In one embodiment, when the nanodiamonds are provided in a solution, the method comprises heating the carbon source, such as the cathode, after applying the nanodiamonds. The temperature of the carbon source may be elevated to at least 150°C, such as at least 160°C, at least 170°C, or at least 180°C. However, the temperature should not be over 300°C. Useful temperature ranges therefore include for example 150-300°C, 150-250°C, 180-300°C, and 180-250°C. The elevated temperature may be maintained for example for 1-3 hours, such as for about 2 hours. Such as treatment, for example 2 hours at 180°C, may be enough to evaporate water. Organic solvents may evaporate with a lower temperature and/or in a shorter time. After the evaporation, the nanodiamonds are present as solid form on the cathode. However, in one embodiment the nanodiamonds are applied as solid form on the cathode, i.e. not in a solution. In both cases the nanodiamonds must be present as solid form on the cathode before the deposition process is started.

After the nanodiamonds have been applied to the carbon source, and optionally any solvent is evaporated, the deposition process may begin, i.e. the cathodic arc may be formed. The nanodiamonds are in solid and dry form during the deposition process, i.e. not in a solution or in vapor.

The process described in the embodiments can be carried out at substantially low temperatures, such as at room temperature or ambient temperature. In one embodiment the process is carried out at room temperature. Room temperature may be defined for example including the temperature in the range of 15-30°C, such as in the range of 15-25°C, in the range of 20-22°C, or in the range of 20- 30°C.

One example of the cathodic arc method is illustrated in Figure 6. A cathode is provided for leading nanodiamonds. The cathode is a graphite rod having a diameter of 6.35 mm, and seven holes at the one end of the rod having a diameter of 1 .5 mm and a depth of for example 5 mm or 7 mm. The nanodiamonds are provided as 5.5% (w/w) solution in water. 200 μΙ of the solution is applied to the holes. After the application, the graphite rod is heated with a hot plate to 180°C, and the water is evaporated for 2 hours.

Next the nanodiamond-loaded cathode is applied to an assembly containing metal anode which is insulated from the cathode by ceramic spacers. A high voltage DC source is connected to the anode and the cathode to form an arc. Plasma containing C⁺ ions together with charged and neutral nanodiamonds is formed and ejected from the cathode towards the substrate. A layer of nanodiamonds and diamond-like carbon as tetrahedral amorphous carbon is deposited onto the substrate.

With the methods of the embodiments it is possible to deposit more than one layer of nanodiamonds and diamond-like carbon onto the substrate. The layers may be similar or different. For example it is possible to first deposit a layer having a higher nanodiamond content onto the substrate, and the deposit one or more layer(s) having a lower nanodiamond content onto the existing layer, or vice versa. A gradient may be formed in this way having a gradient of nanodiamond content.

In one embodiment the method comprises co-depositing two or more layers of nanodiamonds and diamond-like carbon onto the substrate.

In one embodiment the method comprises co-depositing a gradient layer of nanodiamonds and diamond-like carbon onto the substrate.

In one embodiment the diamond-like carbon is tetrahedral amorphous carbon (ta- C). Tetrahedral amorphous carbon is a material high in sp³ hybridized bonds. It is very hard, strong and slicky material. It was noticed in the tests that especially the filtered cathodic vacuum arc method yielded high quality ta-C carbon deposit together with the nanodiamonds.

The method described herein may be used for manufacturing versatile products comprising the codeposited film. The codeposited material comprising or consisting of nanodiamonds and diamond-like carbon is a composite material. In general the present disclosure provides a composite film comprising nanodiamonds and diamond-like carbon, which are in practice the only constituents of the composite material. Only minor amounts of other materials, generally as impurities, may be present, such as less than 0.01 % (w/w), for example less than 0.001 %. Preferably the composite material does not contain boron compounds, nitrogen compounds, fluoride compounds, or (earth) alkaline metals. In one embodiment the composite film consists of nanodiamonds and diamond-like carbon. The mean average diameter of the nanodiamonds may be in the range of 1-25 nm, such as 3-15 nm, or 3-10 nm. In one example 90% of the nanodiamonds in the composite film are in this range, such as 95%, or 99%.

In one embodiment the nanodiamonds in the composite film comprise detonation nanodiamonds, or they consist of detonation nanodiamonds. In one embodiment the detonation nanodiamonds in the composite film are present as agglomerates having a mean average diameter in the range of 2-100 nm. In the tests agglomerates having a mean average diameter in the range of 10-15 nm (about 2-3 DND size) were mostly detected (Figure 7(f)). However bigger agglomerates such as having a mean average diameter of about 50 nm or more are also possible. In one embodiment the detonation nanodiamonds in the composite film are present as agglomerates having a mean average diameter in the range of 2- 25 nm, such as 5-20 nm. In one embodiment the diamond-like carbon in the composite film is tetrahedral amorphous carbon (ta-C). The presence of tetrahedral amorphous carbon can be detected from the final product for example by using Raman spectroscopy or X-ray photoelectron spectroscopy (XPS). In one embodiment the mean average thickness of the film is in the range of 10- 1000 nm. The obtained film thickness may be controlled during the deposition process, and a desired thickness may be obtained. This thickness of the film may be controlled by depositing a desired amount of multiple layers onto the substrate. The thickness of the film may be for example in the range of 10-100 nm, 50-500 nm, or 500-1000 nm.

The final application requirement can be affected by thickness. Tribological applications such as coatings on tools for wear protection would require thicker films, such as 500 nm and above. If optical applications are targeted then films may be thinner, such as few tens of nanometers. Depending on what optical property is targeted the thickness has to be controlled very precisely. This is also the case with sensors. The quality of the ta-C is linked to the process parameters. The DND concentration is linked to the loading conditions and how the deposition progresses. In one embodiment the composite film comprises nanodiamonds in the range of 0.01-50% (w/w). In one embodiment the composite film comprises nanodiamonds in the range of 0.01-10% (w/w).

In one embodiment the composite film comprises nanodiamonds in the range of 0.01-0.5% (w/w). Such an amount of nanodiamonds provide smooth coatings which exhibits hardness, low wear, flexibility and extension capability, even elastic properties. This kind of coating may be used for example in tribological coatings for parts or tools involved in high wear conditions. This kind of coatings may be also used for example for Micro Electro Mechanical systems to form flexible or elastic cantilevers and as coatings for components which can undergo cyclic flexture.

In one embodiment the composite film comprises nanodiamonds in the range of 0.5-1 .0% (w/w). Such an amount of nanodiamonds provide a coating which has good mechanical properties but with enhanced or modified optical properties such as refractive index. This kind of coating may be used for example as a thin film with tailorable refractive index for optical applications with additional benefit of mechanical ruggedness. In one embodiment the composite film comprises nanodiamonds in the range of 1-10% (w/w). Such an amount of nanodiamonds provide a coating which has exceptionally modified optical, electrical and chemical properties. This kind of coating may be used for example as thin film bio-molecule sensor with tailorable sensitivity and selectivity for certain bio-molecules. This kind of coating may also be used for example to form optical waveguides on chip allowing for electro-optical operation.

In one embodiment the composite film is deposited or comprises as gradient of the nanodiamonds in the range of 0-10% (w/w) distributed in the thickness of the composite film. Such a nanodiamond distribution provides a coating which has tailorable mechanical properties as a function of film depth. Furthermore the optical, electrical and chemical properties may also be tailored as a function of depth. This kind of coating may be used for example as a tribological coating with inverse wear properties. This kind of coating may be used for example as an optical waveguide for confinement and propagation of solitons. This kind of coating may also be used for example as an electro-optical guide where electrons as well as photons may be guided simultaneously.

One embodiment provides the composite film described herein as a coating on a substrate. As discussed in previous, the substrate may be selected from silicon, glass, organic polymers, such as plastic, metals and oxides thereof, such as aluminum oxide or titanium oxide.

One embodiment provides the composite film obtained with the method described herein. In the final composite film cubic diamond areas can be detected for example by HRTEM, such as is shown in Figure 7 (c) and (e). Raman spectrum may be used to estimate the quality of the matrix material and to indicate the process used.

The composite films may be used as tribological coatings on a surface. Tribology refers to a study of science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear. The tribological interactions of a solid surface's exposed face with interfacing materials and environment may result in loss of material from the surface. By using the coatings described herein it is possible to reduce the wear and friction of materials, such as metal objects. The materials and objects may be for example engine parts, gear or transmission parts, or any other parts or surfaces thereof, which interact with other parts or surfaces in relative motion. One embodiment provides a metal object, such as a gear or shaft, coated with the composite film.

One embodiment provides a solar cell comprising the composite film. The solar cell may be used in a method for obtaining power from the solar cell, the method comprising exposing the solar cell to light, and obtaining or recovering the electrical power formed in the solar cell.

One embodiment provides a waveguide comprising the composite film, such as an optical waveguide. An optical waveguide is a physical structure that guides electromagnetic waves in the optical spectrum. Examples of optical waveguides include optical fibers and rectangular waveguides. An optical fiber may be a circular cross-section dielectric waveguide comprising dielectric material surrounded by another dielectric material with a lower refractive index. Optical fibers may be made from silica glass, however other glass materials are used for certain applications and plastic optical fiber can be used for short-distance applications.

The optical waveguide may be applied for methods for optical detection of analyte. In one example the composite film is as a coating on an optical fiber and the analyte is detected by plasmonic coupling which would shift the frequency/wavelength of light incident into the fiber.

One embodiment provides a plasmonic sensor comprising the composite film, and a method for detecting an analyte with the plasmonic sensor. Basically if very thin metal films (such as 10-40 nm) are provided and light is incident, then some of the EM radiation couples through the film as an evanescent wave. This technique is used in FTIR where there is prism with metal coating. This is also possible with a metal nano-particle which allow plasmonic coupling. The effect of plasmonic coupling arises from the availability of free electrons which is related to the refractive index and the dielectric nature of the material (Drude's model). This plasmonic coupling may occur with nanomaterials with different electronic distribution (metal nanoparticles or conductive sp² bonded carbon nanoparticles) or nanoparticles with different refractive index (sp³ core in DNDs). When a coating with sufficient number of nanoparticles which are plasmonically active is provided, then when light is passed through they form the evanescent wave very close to the coating which interacts with the analyte. The interaction changes the light (removes some wavelengths or shifts them) and the analyte can be detected from the magnitude and type of change.

One embodiment provides a biomaterial substrate, such as a cell culture support, comprising the composite film.

One embodiment provides an electrochemical device, such as a thin film sensor, comprising the composite film.

The composite films may be used in sensors, such as biosensors or biomolecular sensors, containing a component capable of recognizing an analyte of interest. One embodiment provides a sensor comprising the composite film and an analyte- recognizing component coupled to the composite film. The analyte-recognizing component may be any component, such as an organic, an inorganic or a biological component, compound or molecule, which is capable of recognizing the analyte of interest, preferably capable of specifically recognizing the analyte of interest. The recognizing may be binding to the analyte or other interaction. In the sensor the composite film may be on a substrate such as glass or thermoplastic polymer, for example in a form of a strip or a plate.

According to one definition the biosensor contains a biological component, which is capable of recognizing a specific substrate, and a biomolecular sensor is capable of recognizing a biomolecule, by using biological or non-biological means. Such biosensors or biomolecular sensors may be utilized for example in biotechnology, agriculture, food technology and biomedicine. The sensor may be applied as in-line, on-line, at-line or off-line sensor, for example in analysis of a solution, such as a cultivation broth, dairy product, fermentation solution or the like. The sensor may be used in in vivo or in vitro systems. In vitro measurement takes place in a test tube, a culture dish, a microtiter plate or elsewhere outside a living organism. An in vivo biosensor or biomolecular sensor may be an implantable device that is adapted to operate inside the body.

One embodiment provides a biosensor comprising the composite film and a biological component coupled to the composite film, preferably on a substrate such as glass or thermoplastic polymer, for example a strip or a plate. A biosensor is an analytical device or means which combines a biological component with a physiochemical detector, and which is used for detection of an analyte. The biosensor contains a sensitive biological element, which may be called as biological component or bioreceptor, for example biologically derived material of biomimetic component, which interacts with the analyte of interest. The biological element may be for example a biomolecule from an organism or a receptor modeled after a biological system to interact with the analyte of interest. The interaction may be for example binding or recognition. The interaction changes the properties of the biosensor, which change is detected, for example as a change in electrical current or potential from the biosensor, i.e. a signal is formed.

One embodiment provides a biomolecule sensor comprising the composite film and a biomolecule-recognizing component coupled to the composite film, preferably on a substrate such as glass or thermoplastic polymer, for example a strip or a plate. The component capable of recognizing the biomolecule may be biological or non-biological. A transducer or a detector element transforms the signal resulting from the interaction of the analyte with the component capable of recognizing the analyte, such as with the biological element, into another signal that can be measured and quantified. A sensor, such as biosensor or a biomolecule sensor, is or may be coupled with a corresponding signal processor and electronics, which transduce the detected signal(s) into a readable form. The presence of the analyte may be detected qualitatively or quantitatively.

If electrical potential is detected, the biosensor or biomolecular sensor may be called as a potentiometric biosensor or biomolecular sensor. In a potentiometric sensor the signal is produced by electrochemical and physical changes in the conducting polymer layer due to changes occurring at the surface of the sensor. Such changes can be attributed to ionic strength, pH, hydration and redox reactions, the latter due to the enzyme label turning over a substrate. In an amperometric biosensor or biomolecular sensor the analyte which comes in contact with biological material induces a redox reaction. This results in movement of electrons which is picked up by the transducer and can be detected. One example of an amperometric technique is voltammetry, wherein information about an analyte is obtained by varying a potential and then measuring the resulting current.

In one embodiment the biological component is selected from enzymes, antibodies, nucleic acids, proteins, lipids, tissue, microorganisms, cells, organelles, and cell receptors. The biological component may interact with the analyte of interest with several ways, such as by antibody/antigen interaction, by artificial binding protein, by enzymatic interaction, by affinity binding receptor, or by nucleic acid interaction, such as by nucleic acid-protein interaction. A product of an enzymatic reaction may be detected. When the binding of the sensing element and the analyte is the detected event, the sensor is an affinity sensor. When the interaction between the biological element and the analyte is accompanied or followed by a chemical change in which the concentration of one of the substrates or products is measured the sensor is a metabolism sensor. When the signal is produced after binding the analyte without chemically changing it but by converting an auxiliary substrate, the sensor is a catalytic sensor.

The analyte-recognizing component may be attached to the composite film, more particularly immobilized to the surface of the composite film, for example absorbed or linked, such as by a chemical linkage. The attachment may be by functionalization of the surface, or by three dimensional lattices to chemically or physically entrap the compound, for example by using hydrogel. The surface of the composite film may be functionalized by controlling or modifying the surface termination (H-, O- or NH₂-terminated diamond), to enable covalent grafting of the analyte-recognizing component.

The analyte may be for example a biological component or biomolecule, or another compound or component, such as organic or inorganic molecule. Examples of analytes include pharmaceutical compounds, drugs, steroids, toxins, allergens, disease markers, vitamins, hormones, metabolites, proteins, lipids, carbohydrates, such as glucose, cholesterol, bacteria, viruses, antibodies, DNA, pesticides and the like. The analyte may be detected from a sample, which may be a biological fluid, or any other suitable sample. One embodiment provides a method for detecting the presence of an analyte from a sample, the method comprising

-providing the sensor, wherein the analyte-recognizing component is capable of interacting with the analyte,

-contacting the sensor with the sample,

-detecting electrical current and/or potential from the sensor, wherein the detection of the electrical current and/or potential indicates the presence of the analyte in the sample.

One embodiment provides a method for detecting the presence of an analyte from a sample, the method comprising

-providing the biosensor, wherein the biological component is capable of interacting with the analyte,

-contacting the biosensor with the sample,

-detecting electrical current and/or potential from the biosensor, wherein the detection of the electrical current and/or potential indicates the presence of the analyte in the sample.

The presence of the analyte may refer to qualitative detection, i.e. whether the sample does or does not contain the analyte. The presence of the analyte may also refer to quantitative detection, i.e. the amount of the analyte in the sample may be determined, for example wherein the level or the electrical current and/or potential obtained from the measurement is proportional to the quantity of the analyte in the sample. In such case in the method the detection of the level of the electrical current and/or potential indicates the quantity or level of the analyte in the sample

Examples

Experimental

The deposition system consists of a vacuum chamber which can be evacuated by a mechanical roughing pump and a high vacuum pulp (a cryo pump) to pressures lower than 2e-7 Torr. The p-FCVA system uses 6.35 mm rods of target material and has a pulse forming network and HV supply with max capability of 1 kV. The arc is triggerless and was struck with a frequency of 1 Hz by use of a self designed Labview based software controlling Nl hardware. Without going into details of cathodic arcs when the arc is struck some of the material at the tip of the cathode is ionized and converts into plasma which moves away from the cathode towards the substrate. This property was utilized to co-deposit detonation nanodiamonds (DNDs) and DLC from the same cathode by putting DNDs on the carbon cathode.

5.5 wt% DNDs with average single digit size of 5 nm in stable water suspension (Andante) were acquired from Carbodeon Ltd. Graphite rods with diameter of 6.35 mm and purity of 99.995% were acquired from Graphitestore. Several different methods of putting DNDs on the carbon cathode were tested before the final geometry was selected. The final geometry consists of 7 holes (1 in the center and 6 outside) each with a diameter of 1 .5 mm with a depth of around 5 mm. 100 μΙ of DND solution was drop cast into the holes and then the graphite rod was dried on a hot plate at 200°C for 120 mins. After the elapsed time of 120 mins the graphite rod was removed from hot plate and allowed to cool and the charging procedure was repeated once more. Intrinsic silicon (100) cut into 3 cm x 2 cm were used as substrates. The substrates were ultrasonically cleaned in HPLC grade acetone and blow dried by N₂ gas. For TEM analysis salt crystals (Tedpella) were used as substrates. The salt crystals were cleaved into 1 cm x 1 cm pieces and brush cleaned by HPLC grade acetone to get rid of debris. Once film was deposited onto the salt crystals they were put film side up in a shallow bath of Dl water till the film delaminates. The film was fished out onto M75 copper only TEM grids (Agar) and used for analysis. For comparative TEM analysis base DND solution was diluted to 0.05 wt% and drop cast onto 400 mesh copper grids with carbon film (Agar). Film thicknesses of 50 nm (500 pulses) was deposited for DLC and DND-DLC for comparative analysis. The substrate was placed 1 10 mm away from plasma filter coil at floating potential and room temperature. Substrate was rotated at 20 rpm to ensure uniform film thickness over the whole area. Deposition rate was checked for both DLC and DND-DLC composite film by depositing multiple samples with known number of pulses on a masked Si substrate at 1 10 mm distance and checking the film thickness by contact profilometer (Dektak 6M). Deposition rate was found to be around 0.1 nm/pulse for both DLC and DND-DLC composite film at 1 10mm substrate to filter coil distance.

TEM analysis was performed by Tecnai F-20 (FEI) TEM operating at 200 kV. SEM analysis of the samples was performed by Hitachi S-4700 SEM. Raman spectroscopy was performed by Horiba LabramHR confocal system with 100x objective (Olympus) and spot size of 1 μιτι and aperture size of 1000 μιτι to maximize the signal from DNDs. Ar laser wavelength 488 nm was used with power of 10 mW on the sample.

Nano wear and Nano indentation tests were performed using TI-900 (Hysitron Inc) system using a Berkowitz tip (nominal diameter 200 nm). For both DND-DLC and reference DLC films, to reduce contribution of the silicon substrate the nano- indentation testing was performed in two stages. In the first stage 10 point indentation was performed to estimate the optimal depth from load-displacement curves. In the second stage, a new area was selected and 12 points were indented in a displacement controlled manner set for the optimal depth as found from previous stage. Wear tests were performed at 4 points with loads of 50 μΝ to 200 μΝ and increments of 50 μΝ. Each wear point scan area was 1 umX1 um and tests were performed with 2 scan passes and 4 scan passes to compare the wear with increase in scan pass. Post wear images were acquired by using small force of 1 .5 μΝ and image area was 3 m x 3 μιτι. The wear images were analysed by Gwyddion and average crater depth and average crater area was calculated for each load. Wear volume ratio was calculated as the ratio of crater wear volume to the maximum possible wear volume (film thickness x 1 μιτι²).

Results

Cross section SEM imaging of DND-DLC, shown in Figure 1 indicates the film thickness to be around 55 nm ± 3 nm which compares well with expected film thickness of 50 nm. The HR-TEM and diffraction patterns from the original DND solution drop cast onto TEM grid are shown in Figure 2. The d-spacing from diffraction data of original DND (Figure 2 (b)) matches with values in literature for cubic diamond. HR-TEM images show the DNDs embedded in a matrix of amorphous DLC (Figure 3(a)). The diffraction patterns (Figure 3(b)) correspond to diamond crystal structure and d-spacing calculated from patterns matches well with literature. Another analysis was made with more clear results as shown in Figures 7 (a)-(d). Raman spectra was acquired and fitted by two peaks for D and G regions of amorphous carbon as per literature. I(D)/I(G) ratios calculated for 50 nm thick films from 3 random points each and averaged show no substantial difference in l(D)/l(G) ratios of the DLC and DND-DLC films. However the DND peaks (expected around 1325-1332 /cm) are not visible in Raman, most probably due to low concentration of DNDs in the DLC matrix. Representative plots with D and G peak fittings are shown in Figure 4.

Nanoindentation data was acquired by process as explained in experimental section. The data acquired was analysed by Hysitron Inc software using Oliver- Pharr method. The tip area function was calibrated before and after the indentation and wear tests. Figure 5(a) shows the plot of 12 point hardness for both reference DLC and DND-DLC for both area functions. For both samples the average value of hardness was calculated by averaging the 12 points and further averaged for area function. The average hardness for reference DLC film is around 30 GPa, which matches literature while for the DND-DLC the average hardness is around 35 GPa. The wear volume ratio plots are shown in Fig-5 (b). The red line separates 2 pass plot from 4 pass plot. It can be observed from the wear volume ratio plot (Figure 5(b)) that the wear ratio of reference DLC increases sharply as the load and number of passes increase. Comparatively the DND-DLC wear volume ratio has only a modest increase over the whole range of loads and passes. The nanoindentation data indicates that the DND-DLC is harder than reference DLC and also wears less.

Claims

1 . A method for co-depositing nanodiamonds and diamond-like carbon onto a substrate with physical vapor deposition (PVD) method, the method comprising

-providing a substrate,

-providing a source of ionized carbon plasma,

-providing a source of nanodiamonds,

-ejecting the nanodiamonds and the ionized carbon plasma towards the substrate to co-deposit the nanodiamonds and diamond-like carbon onto the substrate.

2. The method of claim 1 , wherein the source of ionized carbon plasma comprises solid carbon.

3. The method of claim 2, wherein the solid carbon comprises solid graphite.

4. The method of any of the preceding claims, wherein the mean average diameter of the nanodiamonds is in the range of 1-25 nm, such as 3-10 nm.

5. The method of any of the preceding claims, wherein the nanodiamonds comprise detonation nanodiamonds.

6. The method of claim 5, wherein the detonation nanodiamonds are present as agglomerates having mean average diameter in the range of 3-100 nm.

7. The method of any of the claims 1-6, wherein the physical vapor deposition method is DC Magnetron Sputtering method.

8. The method of any of the claims 1-6, wherein the physical vapor deposition method is RF Magnetron Sputtering method.

9. The method of any of the claims 1-6, wherein the physical vapor deposition method is Ion beam assisted deposition method.

10. The method of any of the claims 1-6, wherein the physical vapor deposition method is cathodic arc method and the source of ionized carbon plasma comprises a solid cathode.

1 1 . The method of claim 10, wherein the cathodic arc method is un- filtered cathodic arc method.

12. The method of claim 10, wherein the cathodic arc method is filtered cathodic arc method.

13. The method of claim 1 1 or 12, wherein the cathodic arc method is pulsed cathodic arc method, such as cathodic vacuum arc method.

14. The method of any of the preceding claims, wherein the nanodiamonds and the diamond-like carbon are deposited from different sources.

15. The method of any of the claims 1-13, wherein the nanodiamonds and the diamond-like carbon are deposited from the same source, such as from the same electrode, such as from a cathode.

16. The method of claim 15, comprising

-providing a solid graphite cathode comprising one or more apertures for receiving nanodiamonds,

-applying the nanodiamonds to the one or more apertures in the cathode,

-forming an arc with the cathode to provide a source of ionized carbon plasma and to eject the nanodiamonds and the ionized carbon plasma from the cathode to co- deposit the nanodiamonds and diamond-like carbon onto the substrate.

17. The method of claim 16, comprising providing nanodiamonds in a solution.

18. The method of claim 17, comprising heating the cathode after applying the nanodiamonds.

19. The method of any of the claims 10-18, wherein the nanodiamonds are present as solid form on the cathode.

20. The method of any of the preceding claims, wherein the process is carried out at room temperature, such as at a temperature in the range of 20- 30°C.

21 . The method of any of the preceding claims, comprising co-depositing two or more layers of nanodiamonds and diamond-like carbon onto the substrate.

22. The method of any of the claims 1-20, comprising co-depositing a gradient layer of nanodiamonds and diamond-like carbon onto the substrate.

23. The method of any of the preceding claims, wherein the diamond-like carbon is tetrahedral amorphous carbon (ta-C).

24. The method of any of the preceding claims, wherein the substrate is selected from silicon, glass, organic polymers, such as plastic, metals and oxides thereof, such as alumina or titania.

25. A composite film comprising nanodiamonds and diamond-like carbon.

26. The composite film of claim 25, wherein the mean average diameter of a nanodiamond is in the range of 1 -25 nm, such as 3-10 nm.

27. The composite film of claim 25 or 26, wherein the nanodiamonds comprise detonation nanodiamonds.

28. The composite film of claim 27, wherein the detonation nanodiamonds are present as agglomerates having mean average diameter in the range of 3-100 nm.

29. The composite film of any of the claims 25-28, wherein the diamondlike carbon is tetrahedral amorphous carbon (ta-C).

30. The composite film of any of the claims 25-29, wherein the mean average thickness of the film is in the range of 10-1000 nm.

31 . The composite film of any of the claims 25-30, comprising nanodiamonds in the range of 0.01-50% (w/w).

32. The composite film of claim 31 , comprising nanodiamonds in the range of 0.01-0.5% (w/w).

33. The composite film of claim 31 , comprising nanodiamonds in the range of 0.5-1 .0% (w/w).

34. The composite film of claim 31 , comprising nanodiamonds in the range of 1 .0-10% (w/w).

35. The composite film of any of the claims 25-30, comprising a gradient of the nanodiamonds in the range of 0-10% distributed in the thickness of the composite film.

36. The composite film of any of the claims 25-35 as a coating on a substrate.

37. The composite film of claim 36, wherein the substrate is selected from silicon, glass, organic polymers, such as plastic, metals and oxides thereof, such as aluminum oxide or titanium oxide.

38. The composite film of any of the claims 25-37 obtained with the method of any of the claims 1-24.

39. A metal object, such as a gear or shaft, coated with the composite film of any of the claims 25-38.

40. An electrochemical device, such as a thin film sensor, comprising the composite film of any of the claims 25-38.

41 . A waveguide comprising the composite film of any of the claims 25-

38.

42. A biomaterial substrate, such as a cell culture support, comprising the composite film of any of the claims 25-38.

43. A sensor comprising the composite film of any of the claims 25-38 and an analyte-recognizing component coupled to the composite film.

44. The sensor of claim 43, wherein the analyte-recognizing component is a biological component selected from enzymes, antibodies, nucleic acids, proteins, lipids, tissue, microorganisms, cells, organelles, and cell receptors.

45. A biomolecule sensor comprising the composite film of any of the claims 25-38 and a biomolecule-recognizing component coupled to the composite film.

46. A solar cell comprising the composite film of any of the claims 25-38.

47. A method for detecting the presence of an analyte from a sample, the method comprising

-providing the sensor of claim 43 or 44, wherein the analyte-recognizing component is capable of interacting with the analyte,

-contacting the sensor with the sample,