Дисертації з теми "Quantum Dots - SiOx Matrix"

The connection between light emission and structure of Germanium nanoparticles (3-10 nm) prepared by top-down (etching) and bottom-up (sol-gel and colloidal synthesis) has been investigated using Raman spectroscopy, TEM, x-ray absorption spectroscopy (XAS), x-ray di raction (XRD), and photoluminescence (PL). It was found that TEM, Raman spectroscopy, PL, and XRD techniques all result in di ering values for the nanoparticle size which don't all agree in the limit of experimental error. Several structural models have been proposed and tested by high pressure Raman measurements. It was found that a Raman peak corresponding to diamond-type Ge structure is observed well above the transition pressure of both amorphous ( six GPa) and crystalline ( 11 GPa) Ge. The pressure dependence of the Raman signal peak position was observed to follow an unexpected non-linear shift with a corresponding increase in peak width (FWHM). Possible structural origins of these trends have been investigated by adapting the widely used phonon con nement model to high pressure conditions and comparing experimental data with the model behaviour under assumptions of constant, and size-dependent bulk modulus. Considered collectively with the ambient structural data, the results of the analysis of the high pressure behaviour point to the phenomenon of gradual surface induced amorphisation under pressure in matrix-free Ge nanoparticles. The best structural model to describe this is a core-shell with the small crystalline core and a disordered surface layer. The local structure of samples was investigated using XAS, while opticallydetected XAS, using x-ray excited optical luminescence (XEOL), was used to link structure with optical emission. The emission was found to depend on surface termination; in oxygen terminated nanoparticles the oxide rich regions are responsi- 4 ble for light emission, while in their hydrogen terminated counterparts' pure Ge regions contribute to the luminescence. Furthermore, with the aid of molecular dynamics simulations it was shown that in hydrogen-terminated samples, optical emission is due to a topologically disordered (amorphous) region close to the surface of the nanoparticles. We demonstrated that OD-XAS can potentially provide subnanoparticle resolution due to its sensitivity to the light emitting sites in a sample. We further investigated the microscopic origins of such sensitivity and identi ed possible limitations. This work clearly demonstrates that a combination of methods sensitive to short-range and long-range structure are required for comprehensive characterisation of nanoscale systems.

Materials for the generation and detection of long wavelength IR radiation continue to be of considerable interest for many applications such as night vision, defense and security, rescue, life sciences, industrial processing etc. For this purpose photodetection based on InSb is a well known technology in mid wavelength (3-5 μm) range. One of the ongoing projects in IMAGIC centre has been working on the development of technologies for the next generation long wavelength infrared (LWIR) photodetector focal plane arrays (FPAs) based on a ‘dot to bulk’ concept. A promising potential of this type photodetector exists to extend the detection wavelength to LWIR by using InSb QDs in InAs matrix, which also enable the device to operate at higher temperatures. Although, it is a novel and promising concept but still some challenges like optimization of material quality and device dark current etc are to be addressed. This project work has been focused on the optical and structural characterization of various size InSb QDs embedded in InAs matrix grown on InAs substrate by molecular beam epitaxy (MBE). The InSb QD’s base diameter, height and density have been revealed and evaluated by Atomic force microscopy (AFM) and transmission electron microscopy (TEM). Strong QDs related photoluminescence (PL) signals in IR range have been observed which can be attributed to interband transition between the InSb QDs (holes) and their InAs matrix (electrons). The absorption measurement results show that high absorbance is in the corresponding IR wavelength range which is in agreement with PL measurement results. The experimental results concluded from this work provide valuable information to optimize the InSb QDs materials for designing and fabricating desired LWIR photodetectors with low dark current and high photoresponsivity.

Philosophiae Doctor - PhD
Electroanalytical and optical properties of nanoscale materials are very important for biosensing applications as well as for understanding the unique one-dimensional carrier transport mechanism. One-dimensional semiconductor nanomaterials such as semiconductor quantum dots are extremely attractive for designing high-density protein arrays. Because of their high surfaceto-volume ratio, electro-catalytic activity as well as good biocompatibility and novel electron transport properties make them highly attractive materials for ultra-sensitive detection of biological macromolecules via bio-electronic or bio-optic devices. A genosensor or gene based biosensor is an analytical device that employs immobilized deoxyribonucleic acid (DNA) probes as the recognition element and measures specific binding processes such as the formation of deoxyribonucleic acid-deoxyribonucleic acid (DNA-DNA), deoxyribonucleic acid- ribonucleic acid (DNA-RNA) hybrids, or the interactions between proteins or ligand molecules with DNA at the sensor surface.In this thesis, I present four binary and two ternary-electrochemically and optically modulated selenide and telluride quantum dots, all synthesised at room temperature in aqueous media. Cationic gallium (Ga3+) synthesized in form of hydrated gallium perchlorate salt[Ga(ClO4)3.6H2O] from the reaction of hot perchloric acid and gallium metal was used to tailor the optical and electrochemical properties of the selenide and telluride quantum dots. The synthesized cationic gallium also allowed successful synthesis of novel water soluble and biocompatible capped gallium selenide nanocrystals and gallium telluride quantum dots. Cyclic voltammetric studies inferred that presence of gallium in a ZnSe-3MPA quantum dot lattice improved its conductivity and significantly increased the electron transfer rate in ZnTe-3MPA.Utraviolet-visible (UV-vis) studies showed that incorporation of gallium into a ZnSe-3MPA lattice resulted in a blue shift in the absorption edge of ZnSe-3MPA from 350 nm to 325 nm accompanied by decrease in particle size. An amphiphilic bifunctional molecule, 3-Mercaptopropionic acid (3-MPA) was used as a capping agent for all quantum dots. It was found that 3-MPA fully solubilised the quantum dots, made them stable, biocompatible, non agglomerated and improved their electron transfer kinetics when immobilized on gold electrodes.Retention of the capping agent on the quantum dot surface was confirmed by Fourier transform infrared spectroscopy (FTIR) which gave scissor type bending vibrations of C-H groups in the region 1365 cm-1 to 1475 cm-1, stretching vibrations of C=O at 1640 cm-1, symmetric and asymmetric vibrations of the C-H in the region 2850 cm-1 to 3000 cm-1 as well as stretching vibrations of –O-H group at 3435 cm-1. The particle size and level of non-agglomeration of the quantum dots was studied by high resolution transmission electron microscopy (HRTEM). The optical properties of the quantum dots were studied using UV-vis and fluorescence spectroscopic techniques.Quantum dot/nanocrystal modified gold electrodes were prepared by immersing thoroughly cleaned electrodes in the quantum dot/nanocrystal solution, in dark conditions for specific periods of time. The electrochemical properties of the modified electrodes were characterized by cyclic voltammetry (CV), square wave voltammetry (SWV), electrochemical impedance and spectroscopy (EIS). Six sensing platforms were then prepared using quantum dot/nanocrystal, one of which was used for detection of dopamine while the rest were used for detection of a DNA sequence related to 5-enolpyruvylshikimate-3-phosphate synthase, a common vector gene in glyphosate resistant transgenic plants.The first sensing platform, consisting of ZnSe-3MPA modified gold electrode (Au|ZnSe-3MPA) gave rise to a novel method of detecting dopamine in presence of excess uric acid and ascorbic acid. Using a potential window of 0 to 400 mV, the ZnSe-3MPA masked the potential for oxidation of uric and ascorbic acids, allowing detection of dopamine with a detection limit of 2.43 x 10-10 M (for SWV) and 5.65 x 10-10 M (for steady state amperometry), all in presence of excess uric acid (>6500 higher) and ascorbic acid (>16,000 times higher). The detection limit obtained in this sensor was much lower than the concentration of dopamine in human blood(1.31 x 10-9 M), a property that makes this sensor a potential device for detection of levels of dopamine in human blood.The other sensing platforms were prepared by bioconjugation of amine-terminated 20 base oligonucleotide probe DNA (NH2-5′-CCC ACC GGT CCT TCA TGT TC-3′) onto quantum dot modified electrodes with the aid of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The prepared DNA electrodes were electrostatically hybridized with different sequences which included 5′-GAA CAT GAA GGA CCG GTG GG-3′ (complementary target), 5′-CATAGTTGCAGCTGCCACTG-3′ (non complementary target) and 5′-GATCATGAAGCACCGGAGGG-3′ (3-base mismatched target).The hybridization events were monitored using differential pulse voltammetry (DPV) and SWV by monitoring the guanine oxidation signal or using EIS by monitoring changes in the charge transfer resistance. The quantum dot genosensors were characterized by low detection limits (in the nanomolar range), long linear range (40 - 150 nM) and were able to discriminate among complementary, non-complementary and 3-base mismatched target sequences.

We introduce new oxygen- and moisture-proof polymer matrixes based on polyisobutylene (PIB) and its block copolymer with styrene [poly(styrene-block-isobutylene-blockstyrene), PSt-b-PIB-b-PSt] for the encapsulation of colloidal semiconductor nanocrystals. In order to prepare transparent and processable composites, we developed a special procedure of nanocrystal surface engineering including ligand exchange of parental organic ligands to inorganic species followed by the attachment of specially designed short-chain PIB functionalized with an amino group. The latter provides excellent compatibility of the particles with the polymer matrixes. As colloidal nanocrystals, we chose CdSe nanoplatelets (NPLs) because they possess a large surface and thus are very sensitive to the environment, in particular in terms of their limited photostability. The encapsulation strategy is quite general and can be applied to a wide variety of semiconductor nanocrystals, as demonstrated on the example of PbS quantum dots. All obtained composites exhibited excellent photostability, being tested in a focus of a powerful white-light source, as well as exceptional chemical stability in a strongly acidic media. We compared these properties of the new composites with those of widely used polyacrylate-based materials, demonstrating the superiority of the former. The developed composites are of particular interest for application in optoelectronic devices, such as color-conversion light-emitting diodes, laser diodes, luminescent solar concentrators, etc.

Dans le but de concevoir un dispositif de contrôle du clignotement des nanocristaux, il était nécessaire de créer un composite à l'état solide pouvant s'intégrer dans ce dispositif. Nous avons donc encapsulé des boites quantiques (BQs) à base de cadmium dans une matrice cristalline de pérovskite hybride de bromure de plomb. Ce manuscrit retrace l'ensemble des étapes qui ont été validé pour atteindre la création de ce nouveau composite. Nous avons développé avec succès une synthèse de BQs résistantes à l'encapsulation dans une matrice ionique mais également un échange de ligands inorganiques qui nous a permis d'intégrer de manière efficace les nanocristaux au sein de leur matrice en conservant leurs propriétés de luminescence. Après encapsulation, nous avons pu mettre en avant des preuves montrant une encapsulation efficace et un couplage entre les BQs et la matrice. Ces deux critères sont favorables à l'utilisation de ce composite dans le dispositif de contrôle. Ce dispositif consiste in fine à suivre optiquement la luminescence des BQs et à appliquer un champ électrique pour extraire et évacuer les charges en excès, qui sont à l'origine de l'état non émissif. Le développement de cette partie nous permettra dans le futur d'étudier le phénomène de clignotement mais surtout d'obtenir une source de photons uniques stable et à la demande
To construct a device for controlling the blinking of nanocrystals, it was necessary to create a solid-state active material that can be integrated in such an apparatus. To this end, we have encapsulated cadmium-based quantum dots (QDs) in a crystalline matrix of a hybrid lead-bromide perovskite. This manuscript describes all the steps that have been undertaken to achieve the creation of this new composite. We have developed a synthesis of QDs that are resistant to encapsulation in an ionic matrix by means of an organic-inorganic ligand exchange that allowed us to integrate nanocrystals into the matrix while conserving their luminescence properties. We were thus able to document efficient encapsulation and a coupling between the QDs and the matrix. These two characteristics are favorable for using this composite in a control device which ultimately aims at optically following the luminescence of the BQs and applying an electric field to extract and evacuate the excess charges responsible for the nonemissive state. The successful completion of this step will enable us in the future to study the phenomenon of blinking and, more importantly, to construct a stable on-demand single-photon source

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The scientific advances we have experienced in recent decades have enabled us to produce systems in the mesoscopic scale. These systems have become very useful as research tools in various areas of science. In mesoscopic physics the ondulatory characteristic of electrons is more evident than in classical physics and the electron conduction process is better represented by the wave function that describes it. Examples of application of mesoscopic systems are quantum dots which are open cavities where electrons are limited to flow through. Thus, the objective of this work is to study the effects of decoherence in the transport of electrons in two systems: i) quantum dot with a fictitious guide and ii) quantum dot with stub, where we take into account ondulatory properties of electrons. The formalism that we use is the scattering matrix, which relates the incoming and outgoing amplitudes in the scattering of waves coming in and out of the scattering region. Since the studied systems are chaotic, the scattering matrices can be treated as random. These matrices were generated by computational simulation and then the conductance values were computed. The conductance distribution was obtained by means of probabilistic analysis.
Os avanços científicos que temos experimentado nas últimas décadas proporcionaram a construção de sistemas em escala mesoscópica. Esses sistemas tornaram-se muito úteis como ferramentas de investigação em diversas áreas da ciência. Na física mesoscópica a característica ondulatória dos elétrons é mais evidente do que na física clássica e o processo de condução dos elétrons é melhor representado pela função de onda que os descreve. Exemplos da aplicação de sistemas mesoscópicos são os pontos quânticos que são cavidades abertas por onde os elétrons são limitados a fluirem. Dessa forma, o objetivo deste trabalho é estudar os efeitos da decoerência no transporte de elétrons em dois sistemas: i) ponto quântico com guia fictício e ii) ponto quântico com estube, onde levamos em consideração as propriedades ondulatórias dos elétrons. O formalismo que utilizamos é o da matriz de espalhamento, a qual relaciona as amplitudes das ondas que entram e saem da região de espalhamento. Como os sistemas estudados são caóticos, as matrizes de espalhamento podem ser tratadas como aleatórias. Geramos estas matrizes por meio de simulação computacional e delas extraímos a condutância do sistema. A distribuição da condutância foi obtida por meio de uma análise probabilística.

This thesis is devoted to the optical properties of low-dimensional structures based on such two-dimensional materials as graphene, silicene and phosphorene. We investigate optical properties of a variety of quasi-one dimensional and quasi-zero-dimensional structures, which are promising for future optoelectronics. Primarily we focus on their low-energy optical properties and how these properties are influenced by the structures’ geometry, external fields, intrinsic strain and edge disorder. As a consequence of this endeavor, we find several interesting effects such as correlation between the optical properties of tubes and ribbons whose periodic and ‘hard wall’ boundary conditions are matched and a universal value of matrix element in narrow-gap tubes and ribbons characterizing probability of transitions across the band gap opened up by intrinsic strain originating from the tube’s surface curvature or ribbon’s edge relaxation. The analytical study of the gapped 2D Dirac materials such as silicene and germanene, which have some similarity to the aforementioned quasi-one-dimensional systems in terms of physical description, reveals a valley- and polarization-dependent selection rules. It was also found that absorption coefficient should change in gapped materials with increasing frequency and become a half of its value for gap edge transitions when the spectrum is linear. Our analysis of the electronic properties of flat clusters of silicene and phosphorene relates the emergence and the number of the peculiar edge states localized at zero energy, so-called zero-energy states, which are know to be of topological origin, to the cluster’s structural characteristics such as shape and size. This allows to predict the presence and the number of such states avoiding complicated topological arguments and provides a recipes for design of metallic and dielectric clusters. We show that zero-energy states are optically active and can be efficiently manipulated by external electric field. However, the edge disorder is important to take into account. We present a new fractal-based methodology to study the effects of the edge disorder which can be applied also to modeling of composite materials. These finding should be useful in design of optoelectronic devices such as tunable emitters and detectors in a wide region of electromagnetic spectrum ranging form the mid-infrared and THz to the optical frequencies.

碩士
國立臺北科技大學
光電工程系
106
Inorganic perovskite quantum dots (CsPbX3, X=Cl, Br, I) have the characteristics of narrow FWHM, high quantum yield, and simple synthesis methods, and the emission wavelength can be adjusted from 410 nm to 700 nm. However, the poor stability of CsPbX3 QDs under wet conditions is still considered to be a problem. To overcome this problem, we have incorporated high molecular weight polymers (PMMA) into CsPbBr3 QDs to improve their stability and maintain their excellent optical properties. In this dissertation, the solution of CsPbBr3 perovskite quantum dots was prepared by uniformly mixing Cs2CO3, PbO, TOAB powder, oleic acid, toluene and other solvents, and using a centrifuge and a vacuum pump to prepare high-quality quantum dot powders. Hexane was used as a dispersant for the quantum dot powder to complete the preparation of the quantum dot solution. Finally, a solution with different proportions of quantum dots CsPbBr3 and PMMA was prepared and discussed. In the preparation of thin films, firstly, a thin film with the structure of Glass / QD-CsPbBr3 / PMMA was fabricated in a Glove box using a well-developed quantum dot CsPbBr3 solution by changing the ratio of CsPbBr3:PMMA. Observe the differences in photoluminescence intensity, absorbance, and material properties. For the thin film and material analysis of quantum dot CsPbBr3, the analysis was performed with photoluminescence (PL), transmittance and absorbance (Transmittance/Absorbance), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The properties of optical properties, structures, and morphology were further investigated to investigate the effect of doped PMMA on perovskite CsPbBr3 quantum dots.

碩士
國立交通大學
光電工程研究所
106
Quantum dots are widely employed in many electric devices and photonic devices, such as memory, light emitting diodes, photodetectors and photovoltaic in recent decades. Among many materials, the Si quantum dot (Si QD) thin films are potential candidates due to the abundance, environment friendly and keeping the advantages in another kinds quantum dots. In many researches, the Si QDs often are embedded in silicon based dielectric materials. Although the optical properties have advantages mentioned above in Si QD thin films, the transport of carriers are limited by the high resistivity of dielectric materials. The performances are not as expected. Therefore, zinc oxide (ZnO) is adopted to replace the high resistivity dielectric materials since the wide-bandgap (3.1-3.3eV) property which can not only confine the Si QDs but also enhance the light absorption of short wavelength so that these had great potential to improve efficiency of photovoltaic device. In 2011, we proposed Si QDs embedded in ZnO matrix by utilizing Si/ZnO multilayer thin film structure. However, the occurrence of local film prominences in ZnO thin films is observed, which is due to the increased interior film stress resulting from the phase transformation of a- to nc-Si QDs. In this study, we propose three multilayer structures by co-sputtering to eliminate the local film prominences. In first structure, the SiO2 is co-sputtered with Si to raise the content of oxygen and form the Si rich oxide (SRO) in the multilayers of ZnO and Si alternate deposition. The SiOx would form to be buffer layer to reduce the strain produced by c-Si QDs. In second structure, we used the gradient concentration of Si in ZnO and formed GSZO thin films to disperse the strain produced by c-Si QDs. In the third structure, we used the lowly Si doped ZnO (LSZO) to replace the ZnO due to the better characteristics than ZnO and Si Rich in ZnO (SRZO) to substitute the Si layer because of the result in first part. There were 20 periods alternate deposition by LSZO and HSZO in the multilayer. After annealing the amorphous Si QDs would form. We analyzed the optical and electrical properties in this multilayer and deposited it on the p-type Si substrate to measure the characteristics of photovoltaic device. Finally, we used the forming gas (N2: H2=95:5) annealing to enhance the photonic properties.

In this thesis, the structural, optical and electrical properties of crystalline silicon quantum dots (SiQDs) are examined for application to silicon based tandem cells. The approach has been to concentrate on all silicon devices by taking advantage of quantum confinement in low-dimensional Si. RF magnetron co-sputtering provided the capability of creating superlattice structures in conjunction with high temperature annealing, to form Si nanocrystals in an oxide matrix. Structural techniques, including Fourier transform infrared spectroscopy (FTIR), micro-Raman spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Secondary ion mass spectroscopy (SIM) were employed to gather structural information about the SiQD/SiO2 SLs. The result combine presents that the packing density of Si QDs, correlated to the oxygen content of the silicon rich oxide layer can be control independently. The effect of Si nanocrystallite density on Raman scattering is investigated. The preliminary results present that a decrease in the oxygen content (x) results in an increased sharpness of the Strokes-mode peak of nanocrystalline Si, attributed to an increase in the proportion of crystalline Si because of the increased number of SiQDs. However the influence of the surface region on the crystallite core intensity scattering becomes dominant, when SiQD size diameter is very small (less than 3 nm). The present work shows that a decrease in x-content leading to an increase of the SiQD concentration, initially results in the enhancement of the lateral conductivity in the SiQD superlattice material. In this work, the Al contacting scheme, using a prolonged heat treatment technique at elevated temperature less than the eutectic point of Al and Si (577C) has been successfully applied to making Ohmic contacts on both SiQD SLs in oxide and nitride matrices. Activation energy (Ea) of SiQDs, extracted from a linear Arrhenius plot is investigated in the present work in order to expand the understanding of engineering electrical injection in laterally active paths. It is found that a lower barrier height of dielectric matrix influences to the lateral electron transport of the SiQDs in such dielectric matrix. PL results confirm that the band gap of surface oxidized SiQDs widens due to quantum confinement. The present results reveal that the strong peak (Q-peak) due to quantum confinement is more effective in the emission with increasing SiQD concentration. The surface oxide is believed to play an important role in the reduction of SiQD luminescence due to a trapped exiciton. It is concluded that SiQDs surface oxide accompanied by a SiO2 matrix may not provide a good passivation in very small SiQD size. However the energy band gap and conductivity of the SiQDs are tunablity, in the optimum range of SiQD size and concentration. This observation may be important for future nanoelectronics applications.

碩士
國立中山大學
化學系研究所
96
Abstract Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a powerful tool for the analysis of biomolecules such as peptides and proteins and soft ionization technique using the organic matrix. Because of the high concentration of the organic matrix produces high background signals in the low mass range, nanopatticles have been intensively applied in the surface-assisted Laser desorption/ionization-mass spectrometry (SALDI-MS) to reduce the background interferences in the MALDI.-MS. This thesis includes two projects. The first project applied the copper oxide nanorods, which absorbs 337 nm UV laser energy and has the large area, as the matrix for SALDI-TOF MS to detect four large antibiotics, peptides and proteins. The optimized conditions of the four antibiotic drugs were: 1000 μM of copper oxide nanorods and incubation for 30 minutes to get the best signals. The LODs of the Lasalocid, Monensin, Salinomycin and Narasin are 200 nM, 25 nM, 50 nM and 50 nM, respectively. In addition, in this project, the CuO nanorods also can be mixed with glycerol to enhance the detection sensitivity for peptides and proteins. The second project presents the zinc selenium quantum dots (ZnSe QDs) modified with 3-mercaptopropionic acid (3-MPA) as the matrix and affinity probes in the SALDI-TOF MS. It strengthens the interaction between the gramicidin and zinc selenium quantum dots by electric interaction in the pH 6 phosphate buffer solution according to the pI value of the gramicidin and the pKa of. 3-mercaptopropionic acid. The best sensitivity of the gramicidin can be obtained under the optimized conditions: 50 μM of zinc selenium quantum dots, 30 minutes incubation time and pH 6 of phosphate buffer solution. The LOD of the gramicidin is 0.08 μM. This approach also can be successfully applied in the SALDI-TOF MS to enhance the sensitivity of peptides and proteins.

碩士
中原大學
生物醫學工程研究所
105
Because of eco-friendly issues, quantum dot nano fluorescent probes composed of heavy metal materials encounter challenges. Applications of quantum dots materials also face impact, such as light-emitting diode emitting from quantum dots fluorescence, biomarker, cell tracking, molecule tests. Scientists increasingly emphasize on fluorescent nano probes composed of eco-friendly materials. Fluorescent gold quantum clusters based on gold precursor and fluorescent carbon quantum dots made up of carbon, oxygen, nitrogen have been replacing quantum dots materials with bio hazard. In this study, utilizing different ratios mixture of carbon quantum dots with blue fluorescence and gold quantum clusters with yellow fluorescence, violet light and blue light-emitting diode emits white fluorescence. Moreover, white fluorescent materials is added in polymer solution (PEGDA) containing curing agents (HMPP) and polymer solution is solidified under violet light to form a thin film. Patterned sapphire substrate(PSS) with microstructures is imprinted on fluorescent the thin film to make the thin film have microstructures. Optical waveguide is solved due to thin film’s high refractive index and efficiency of light extract is further enhanced. At last, packing fluorescent polymeric thin films with microstructures into violet light and a blue light-emitting diode forms a white light-emitting diode to apply for illumination and biomedical applications in the future.