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Silicon photonics has over the past decade dramatically expanded in scale and importance and now plays a key role in optical communications for data centers, with many longer-term applications such as LIDAR, optical computing, and biomedical sensing. Monolithically integrated light sources based on III-V alloys grown directly on silicon have for decades been a goal in the field, but this has only recently become a commercially feasible approach after steady reductions in defect densities for III-V-on-Si epitaxy and the introduction of quantum dot (QD)-based active regions. This work focuses on improving the reliability of such InAs QD lasers on silicon by understanding their fundamental degradation mechanisms, particularly by studying the evolution and impacts of dislocations. Indium alloying of AlGaAs is demonstrated to halt most dislocation motion and dramatically slow all remaining dislocations via an alloy hardening effect. This leads to the most significant finding of this work: describing a formation mechanism for misfit dislocations around the active region of QD lasers and devising a solution. The misfit dislocations form, in part, due to dislocation pinning through the active region, so thin indium alloyed layers, termed trapping layers, are inserted to extend the pinning effect and displace the dislocations away from the active layers. This yields notable performance improvements but more importantly enhances the reliability of lasers by up to 100×. These trapping layers are later employed for defect reduction in a heterogeneous integration scheme for templated regrowth. The impacts of misfit and threading dislocations on QD luminescence beyond non-radiative recombination is also explored. The source of lingering gradual degradation in QD lasers is clarified through electroluminescence and TEM imaging of aged and unaged lasers. Degradation is spread uniformly across the laser and is caused by growth of non-visible point defects, some of which coalesce into observable dislocation loops. Trapping layers are also explored in quantum well (QW) lasers on silicon to enhance defect filtering and reliability, but it is expected that untrapped misfit dislocations and remaining threading dislocations will limit reliability of such devices. Finally, suggestions are made for future work to improve QD laser reliability by optimizing trapping layer performance and addressing point-defect-based degradation.

Plasma is the state of matter produced when molecules and atoms are energized to a point where their electrons escape and the constituent material becomes ionized. It is described as the fourth state of matter making up the vast majority of the observable universe, and over the past century has been studied and developed into usable human-scale applications. As a category, plasma exists in a thermal spectrum as ionization and unbound electrons are the defining characteristics. Thus, non-thermal plasmas made up of near room temperature ionized gasses formed through strong alternating electromagnetic fields make up one side of the spectrum and thermal plasmas that have heated materials to the point of ionizing constitute the other. This dissertation focuses on the application of non-thermal plasmas for reactive gas generation and nanomaterial synthesis, in addition to more fundamental studies of how the plasma interacts with solid interfaces or forms nanomaterials. The studies that this work is composed of are broken down into sections, the first of which is fundamental investigations of non-thermal plasma properties, such as in-situ monitoring of plasma-induced surface-heating via Raman-thermometry and investigations into nanomaterial growth mechanics when exposed to discontinuous (pulsing) plasma conditions. The second section puts the silicon nanomaterials produced via plasma to use in quantum dots, where the silicon nanocrystal is combined with non-toxic organic molecules to achieve record setting photon upconversion and investigates the fundamental mechanisms impacting this method of light conversion. Next, plasma-grown and commercial silicon nanomaterials are applied as a next generation lithium-ion battery anode material, where unanswered questions about carbon shell structure and solid electrolyte interphase growth are investigated with novel techniques of material production and analysis. Finally, the reactive gas output of a plasma is put to work as a cheap and efficient method of pathogen decontamination for face-piece-respirators, demonstrating the wide breadth of applications for non-thermal plasmas and the materials it can produce.

A novel strategy was developed to fabricate FeNx-doped carbon quantum dots (Fe-N-CQDs) to detect Cu2+ ions selectively as a fluorescence probe. The Fe-N-CQDs were synthesized by an efficient electrolysis of a carbon cloth electrode, which was coated with monoatomic iron-anchored nitrogen-doped carbon (Fe-N-C). The obtained Fe-N-CQDs emitted blue fluorescence and possessed a quantum yield (QY) of 7.5%. An extremely wide linear relationship between the Cu2+ concentration and the fluorescence intensity was obtained in the range from 100 nM to 1000 nM (R2 = 0.997), and the detection limit was calculated as 59 nM. Moreover, the Fe-N-CQDs demonstrated wide range pH compatibility between 2 and 13 due to the coordination between pyridine nitrogen and Fe3+, which dramatically reduced the affection of the protonation and deprotonation process between H+ and Fe-N-CQDs. It is notable that the Fe-N-CQDs exhibited a rapid response in Cu2+ detection, where stable quenching can be completed in 7 s. The mechanism of excellent selective detection of Cu2+ was revealed by energy level simulation that the LUMO level of Fe-N-CQDs (−4.37 eV) was close to the redox potential of Cu2+, thus facilitating the electron transport from Fe-N-CQDs to Cu2+.

High light-harvesting efficiency and low interfacial charge transfer loss are essential for the fabrication of high-efficiency quantum dot-based solar cells (QDSCs). Increasing the thickness of mesoporous TiO2 films can improve the loading of pre-synthesized QDs on the film and enhance the absorbance of photoanode, but commonly accompanied by the increase in the unfavorable charge recombination due to prolonged electron transmission paths. Herein, we systematically studied the influence of the balance between QD loading and TiO2 film thickness on the performance of QDSCs. It is found that the relative thin photoanode prepared by the cationic surfactant-assisted multiple deposition procedure has achieved a high QD loading which is comparable to that of the thick photoanode commonly used. Under AM 1.5G illumination, Zn–Cu–In–Se and Zn–Cu–In–S based QDSCs with optimized 11.8 μm photoanodes show the PCE of 10.03% and 8.53%, respectively, which are comparable to the corresponding highest PCE of Zn–Cu–In–Se and Zn–Cu–In–S QDSCs (9.74% and 8.75%) with over 25.0 μm photoanodes. Similarly, an impressive PCE of 6.14% was obtained for the CdSe based QDSCs with a 4.1 μm photoanode, which is slightly lower than the best PCE (7.05%) of reference CdSe QDSCs with 18.1 μm photoanode.

A composite system consisting of aminosilicate (APS) functionalized-fullerene quantum dots (C60 QDs) and bismuth vanadate (BiVO4-APS-C60) has been developed via a facile one-step hydrothermal process. The structural analysis by XRD revealed that the integrated QDs have not affected the crystal structure of the host BiVO4, while the XPS studies showed that these QDs have been integrated via the Bi-V-O-Si-C network. The optical studies indicated that both the C60 and APS-C60 QDs have hardly influenced the optical absorption properties of the composite system. On the other hand, the dispersion of aminosilicate functionalized-QDs considerably reduced the aggregation in the layers and yielded a few nanometer thick BiVO4 layers due to their inter-layer occupancy as seen from their high-resolution TEM images. The photoluminescence, photocurrent and electrochemical impedance studies showed that the integration of APS-C60 QDs greatly improved the photoactive properties of the composite by effectively enhancing the charge recombination resistance, charge separation and transfer process between the integrated materials and surroundings. As a result, BiVO4-APS-C60 composites showed the enhanced photocatalytic efficiency towards degradation of ciprofloxacin (CIP) molecules under solar light irradiation as compared to that of bare-BiVO4 and BiVO4-C60.

Nanoparticles has become a major part of scientific interest one of the most recent research and applications are done with TiO2 nanoparticles due to its wide range of application in treatment of water, health sector, energy sector and also for the treatment of environment pollutants such as dyes and also in cosmetics the key features of TiO2 nanoparticles involves high surface area that can be utilized for catalytic reactions low toxicity, chemical and physical stability, cost effectiveness and etc. one of its key feature is that is can also be prepared in a green method by using plant extracts acting as stabilizers. It is found in three phases namely Anatase, Rutile and brookite each with is unique applications according to its properties, the application of TiO2 is mainly based upon the modification of the electron-hole pair recombination and the modification in its wide band gap via using the concept of quantum confinement, the absorption range of pure TiO2 nanoparticles is the ultraviolet region is photo catalytically of very less use, the absorption region of TiO2 be prioritized to visible part of the radiation by means of doping metals, non-metals, and semiconductors with narrow band gap which gives composites of TiO2 this can help in the preparation of photocatalyst for the generation of hydroxyl and superoxide radicals which are strong oxidizing, these radical can also be utilized in the treatment purpose of cancer. TiO2 nanoparticles can be prepared by various methodssuch as hydrothermal, sol–gel etc depending upon their application. Also has various shapes like Quantum dots, nanotubes and etc. Classification can also be done on the basis of their photocatalytic products.

Semiconductor Quantum Dots have unique properties, such as the quantum size effect that provide the breakthrough in optoelectronic devices. The small effective mass of electron and hole open-up an avenue of wide bandgap tunability in InAs Quantum Dots (QDs), making them an attractive material for solar cell application. Therein, 4x4 Luttinger Kohn Hamiltonian method is used to calculate the absorption co-efficient of epitaxially grown InAs QDs. Further, we studied the size-dependent absorption co-efficient and the barrier material model of InAs QDs capping with InP and GaAs. Our theoretical simulation predicts the efficiency of InAs/GaAs and InAs/InP system in the intrinsic layer of p-i-n structure solar cells.

The g-C3N4/BiOI/CdS double Z-scheme heterojunction photocatalyst with I3−/I− redox pairs is prepared using simple calcination, solvothermal, and solution chemical deposition methods. The photocatalyst comprised mesoporous, thin g-C3N4 nanosheets loaded on flower-like microspheres of BiOI with CdS quantum dots. The g-C3N4/BiOI/CdS double Z-scheme heterojunction has abundant active sites and in situ redox I3−/I− mediators and shows quantum size effects, which are all conducive to enhancing the separation of photoinduced charges and increasing the photocatalytic degradation efficiency for bisphenol A, a model pollutant. Specifically, the heterojunction photocatalyst achieves a photocatalytic degradation efficiency for bisphenol A of 98.62% in 120 min and photocatalytic hydrogen production of 863.44 μmol h−1g−1 on exposure to visible light. The excellent visible-light photocatalytic performance is as a result of the Z-scheme heterojunction, which extends absorption to the visible light region, as well as the I3−/I− pairs, which accelerate photoinduced charge carrier transfer and separation, thus dramatically boosting the photocatalytic performance. In addition, the key role of the charge transfer across the indirect Z-scheme heterojunction has been elucidated and the transfer mechanism is confirmed based on the detection of intermediate I3− ions. Thus, this study provides guidelines for the design of indirect Z-scheme heterojunction photocatalysts.

Rapid, sensitive, point-of-care detection of pathogenic bacteria is important for food safety. In this study, we developed a novel quantum dot nanobeads-labelled lateral flow immunoassay strip (QBs-labelled LFIAS) combined with strand displacement loop-mediated isothermal amplification (SD-LAMP) for quantitative Salmonella Typhimurium (ST) detection. Quantum dot nanobeads (QBs) served as fluorescence reporters, providing good detection efficiency. The customizable strand displacement (SD) probe was used in LAMP to improve the specificity of the method and prevent by-product capture. Detection was based on a sandwich immunoassay. A fluorescence strip reader measured the fluorescence intensity (FI) of the test (T) line and control (C) line. The linear detection range of the strip was 102–108 CFU·mL−1. The visual limit of detection was 103 CFU·mL−1, indicating that the system was 10-fold more sensitive than AuNPs-labelled test strips. ST specificity was analyzed in accordance with agarose gel outputs of PCR and SD-LAMP. We detected ST in foods with an acceptable recovery of 85%–110%. The method is rapid, simple, almost equipment-free, and suitable for bacterial detection in foods and for clinical diagnosis.

Gd2O3:Eu3+@ CsPbBr3 QDs mesoporous hollow nanocomposites with good luminescent properties and high stability were built. Among which, the hollow Gd2O3:Eu3+ spheres and CsPbBr3 QDs were prepared by urea homogeneous precipitation and hot-injection method, respectively. Finally, the Gd2O3:Eu3+@ CsPbBr3 QDs shell-core compounds were constructed through mechanical stirring. The structure, morphology, stability and luminescent properties were studied by the comprehensive of Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry/thermogravity (DSC/TG), X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence excitation/photoluminescence (PLE/PL) and life decay tools. Compared to the original CsPbBr3 QDs, Gd2O3:Eu3+@ CsPbBr3 QDs display better photostability, thermal stability and current stability. The resulting Gd2O3:Eu3+@ CsPbBr3 QDs composite exhibit good yellow emission. The Gd2O3:Eu3+@ CsPbBr3 QDs mixed silicone resin was directly coated on the blue LED chip, then the w-LED device with the color coordinate of (0.31, 0.32) was successfully assembled. The Gd2O3:Eu3+@ CsPbBr3 QDs compounds with excellent luminescent properties and stability are expected to be widely used in lighting and display areas.

The wide range of applications and promising possibilities of stacked 2D materials highlight the importance of studying heterostructures. The works presented in this dissertation tell a comprehensive story about the heterostructure composed of graphene and hexagonal boron nitride (hBN). Through the use of established characterization techniques such as transport and scanning tunneling microscopy, we will explore phenomena in the graphene/hBN heterostructure from the bottom up in three vertical stages. Stage 1 is the bottommost part of the heterostructure and deals with the accumulation of charged defects in hBN induced by an exposure to high electric fields. Stage 2 focuses on the graphene/hBN interface and how these layered materials work together to enable the corralling of relativistic charge carriers. Finally, stage 3 probes the exposed surface of a double-layered graphene system which is decoupled from hBN while still benefiting from its structural support. The interplay between these materials yields high quality and atomically resolved tunneling spectroscopy results that suggest the emergence of correlated phenomena in naturally occurring double-layered graphene.

Aqueous phase synthesized ternary I–III–VI2 Quantum dots (QDs) are getting more and more attention in biology researches, for their good biocompatibility and easy-to-adjust fluorescence properties. However, the quantum yield (QY) of these aqueous phase synthesized QDs are often pretty low, which seriously hindered their further applications in this field. In general, the ripening of the QDs helps to enhance their QY, closely related to the ripening temperature. But it is still hard to precisely control the fluorescence performance of the QDs products, due to the difficulties in precise temperature control and cumbersome temperature adjusting operations in batch reactors. Here we proposed an integrated droplet microfluidic chip for the automated and successive AgInS2 QDs synthesis and ripening, with both temperatures controlled independently, precisely but easily. Taking advantage of the space-time transformation of the droplet microfluidic chips, the suitable temperature combination for AgInS2 QDs synthesis and ripening was studied, and the high-performance AgInS2 QDs were obtained. In addition, the reason for the decrease of QY of AgInS2 QDs at higher ripening temperature was also explored.

Nanocomposites of graphene quantum dots (GQDs) modified gadolinium oxide (Gd2O3) particles were successfully synthesized. In addition, the effects of the amount of GQDs and the particle size of Gd2O3 on the properties of nanocomposites were investigated. The structures and properties of nanoparticles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence spectrometry, and magnetic resonance imaging. The results show that the synthesized particles Gd2O3/GQD are spherical with a diameter of approximately 40 nm and have excellent fluorescence and magnetic property, and its relaxation rate (r1 = 25.18 (mmol/L)−1/s) is higher than that of the typical commercial contrast agents Gd-DTPA (r1 = 4.5 (mmol/L)−1/s). The fluorescence property of Gd2O3/GQD is optimized by varying the VGQDs:VGd2O3 ratio, and 1:1 ratio of VGQDs:VGd2O3 results in the best fluorescence property. The large particles of Gd2O3 improve the relaxation property of nanocomposites. Therefore, the nanocomposites Gd2O3/GQD with magnetic and fluorescence characteristics can be used in biological imaging, drug targeting, and in-vivo diagnostic analysis.

N-doped reduced graphene oxide quantum dots (N-rGQDs) have attracted more and more attention in efficient catalytic degradation of aqueous organic pollutants. However, the synthesis of N-rGQDs is generally a complex and high energy required process for the reduction and N-doping steps. In this study, a facile and green fabrication approach of N-rGQDs is established, based on a metal-free Fenton reaction without additional energy-input. The N structures of N-rGQDs play a significant role in the promotion of their catalytic performance. The N-rGQDs with relatively high percentage of aromatic nitrogen (NAr-rGQDs) perform excellent catalytic activities, with which the degradation efficiency of pollutant is enhanced by 25 times. Density functional theory (DFT) calculation also indicates aromatic nitrogen structures with electron-rich sites are prone to transfer electron, presenting a key role in the catalytic reaction. This metal-free Fenton process provides a green and cost-effective strategy for one-step fabrication of N-rGQDs with controllable features and potential environmental catalytic applications.

The strong anisotropic electrical properties of one-dimensional (1D) nanostructure semiconductors, especially the anisotropic carrier transport, have a negative and significant influence on the performance of solar cells if the nanostructures have random orientation. Considering the advantages of nanorod solar cells in carrier transport, we have achieved growth of vertically aligned Sb2Se3 nanorod array with highly (hk1) orientation on CdS substrate, and constructed superstrate nanorod solar cells for the first time. The Sb2Se3 nanorod array solar cells exhibit the more efficient and long-range carrier transport in vertical direction. Furthermore, in order to suppress interface recombination, a CuInSe2 quantum dots (QDs) sensitizer has been applied to fill the volume between the nanorods completely, thus forming an interpenetrating nanocomposite structure. The CuInSe2 QDs can harvest additional light by absorption of visible light and contribute photocurrent. Meantime, the QDs function as a hole transport material and thus reduce the dependence of lateral transport. Consequently, the interpenetrating nanocomposite CuInSe2/Sb2Se3 solar cells display a power conversion efficiency of 7.54% with significant enhancements in the short-circuit current density and open-circuit voltage over pure Sb2Se3 nanorod cells. This is the highest efficiency for superstrate solar cells based on Sb2Se3 nanorod arrays.

Benefiting from their high concentration of in-plane nitrogen element, superior chemical/thermal stability, tunable electronic band structure and environmental friendly feature, graphite-like carbon nitride (g-C3N4) as a new promising metal-free material has drawn numerous attention in photo-/electric-catalysis. Comparing to the regulation of band structure in photocatalysis, the deliberately synthesis of g-C3N4 electrocatalysts is mainly focused on the construction of catalytic sites and the modulation of the charge transfer kinetics. Herein, this work reports a rapid method for synthesizing ultrafine g-C3N4 quantum dots (QDs) via electrochemical exfoliation using Al3+ ions. The uniform g-C3N4 QDs with smaller lateral dimension and thickness are collected due to the higher charge density and stronger electrostatic forces of Al3+ ions in the lattice of host materials as compared to the conventional univalent alkali cations. The as-obtained g-C3N4 QDs exhibit average lateral dimension and thickness of 3.5 nm and 1.0 nm, respectively, as determined by the TEM and AFM measurements. Also, the presence of the rich C/N defects is verified by the UV-vis spectra. Encouragingly, the ultrafine g-C3N4 QDs exhibit superior hydrogen evolution reaction (HER) performance with an ultra-low onset-potential closely approaching to 0 V, and a low overpotential of 208 mV at 10 mA/cm2, as well as a remarkably low Tafel slope (52 mV·dec-1) in acidic electrolyte. Taking the fabrication of the ultrafine g-C3N4 QDs with rich C/N defects as an example, this work provides a simple and feasible way to exfoliate 2D layered materials into low-dimensional nanomaterials towards highly-efficient electrocatalysis, as well as the exploration of their fascinating physic-chemical properties.

Compared with other transition metal Mxene derived quantum dots (MQDS), Ta-based Mxene quantum dots have good functionality, but Ta-based Mxene quantum dots and their applications have not been studied so far. In this paper, we report for the first time the synthesis of high fluorescence quantum yield (QY) N-doped Ta4C3 quantum dots (N-MQDs) using Ta4C3 quantum dots in acid reflux damaged Ta4C3 nanosheets as precursors and ethylenediamine as nitrogen source. The prepared N-MQDs have excellent blue photoluminescence (PL) properties, particle size is only 2.60 nm, QY is up to 23.4%, and good stability. In addition, it has been reported that N-MQDs can be used as fluorescent probe for detection of Fe3+ and remote force sensing analysis In liquid ion sensing, N-MQDS shows a unique selective quenching of Fe3+ with a detection limit as low as 2 μmol/L, and has great potential as a fast and super-sensitive fluorescent probe for the detection of heavy ion. More importantly, in solid mechanics sensing, the introduction of N-MQDs into self-healing hydrogels can be developed into a fluorescent hydrogel that can be used for accurate remote force measurement and applied in the field of mechanical sensing analysis. Therefore, Ta-based N-MQDs show excellent potential in the field of fluorescence sensing, which provides a door for multi-dimensional sensing of new materials in the future.

To alleviate the secondary contamination of our environment when using quantum dots (QDs) to detect the organophosphorothioate pesticides (OPPs), we herein report a strategy to assemble magnetic Fe3O4 nanoparticles and luminescent CdTe quantum dots (QDs) into a composite nanosystem, which possesses both the magnetic property of Fe3O4 nanoparticles and the luminescent character of CdTe QDs, for the detection of chlorpyrifos, one of the typical OPPs. This strategy involves the isolated synthesis of magnetic Fe3O4 nanoparticles with positive charges and luminescent CdTe QDs with negative charges, and their subsequent assembly by electrostatic interaction. The as-prepared Fe3O4-CdTe nanocomposites have a detection limit as low as 10 ppb for chlorpyrifos, and are also selective for the OPPs with a phosphorothioate moiety (P=S bond). In specific, the Fe3O4-CdTe nanocomposites can be conveniently harvested by a normal magnet, and the recycling rate for both Cd and Fe determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES) is higher than 96%, showing great potential in alleviating the Cd pollution on the environment.

Accurate single-cell capture is a crucial step for single cell biological and chemical analysis. Conventional single-cell capturing often confront operational complexity, limited efficiency, cell damage, large scale but low accuracy, incompetence in the acquirement of nano-upgraded single-cell liquid. Flow cytometry has been widely used in large-scale single-cell detection, while precise single-cell isolation relies on both a precision operating platform and a microscope, which is not only extremely inefficient, but also not conducive to couple with modern analytical instruments. Herein, we develop a modular single-cell pipette (mSCP) microfluidic chip with high efficiency and strong applicability for accurate direct capture of single viable cell from cell suspensions into nanoliter droplets (30−1000 nL). The mSCP is used as a sampling platform for the detection of CdTe quantum dots in single cells with electrothermal atomic absorption spectrometry (ETAAS) for the first time. It also ensures precise single-cell sampling and detection by inductively coupled plasma mass spectrometry (ICP-MS).

Semiconductor materials have been used for photocatalytic degradation since they were discovered to be useful for photocatalytic degradation. Many studies have been researched to improve the efficiency of photocatalytic degradation. Among them, the introduction of vacancies to improve the photocatalytic efficiency has been verified to be a more feasible method. In this study, we combined two-dimensional (2D) graphite carbon nitride (g-C3N4) nanosheets with oxygen-containing vacancy zero-dimensional (0D) Bi2WO6 (BWO-OV) quantum dots to prepare 2D-0D g-C3N4/Bi2WO6-OV composite catalyst. The use of Bi2WO6 containing oxygen vacancies enhanced the absorption of light and increased the generation of photogenerated carriers. In addition, the formation of heterojunction and the vacancy structure of Bi2WO6 promote the life of photogenerated carriers and improve the catalytic effect of the catalyst. This structure shows high efficiency in removing low concentration (0.5 ppm) of nitric oxide (NO) at room temperature. The efficiency of the composite catalyst is much higher than g-C3N4 or BWO-OV, and better than the composite g-C3N4/Bi2WO6 without oxygen vacancies. When applied to NO removal, the composite g-C3N4/Bi2WO6-OV-10 showed the best catalytic activity which was up to 61.2%. At the same time, five cycles of experiments show that the material has excellent stability.

Quantum dots-hydrogel composites are promising new materials that have attracted extensive attention due to their incomparable biocompatibility and acceptable biodegradability, leading to enormous potential applications for various fields. This review summarizes the recent advances in quantum dots-hydrogel composites with a focus on synthesis methods, including hydrogel gelation in quantum dots (QDs) solution, embedding prepared QDs into hydrogels after gelation, forming QDs in situ within the preformed gel and cross-linking via QDs to form hydrogels. In particularly, biomedical applications as bioimaging, biosensing and drug delivery are also reviewed, followed by a discussion on the inherent challenges of design optimization, biocompatibility and bimodal applications and the prospect of the future development. These results will guide the development of quantum dots-hydrogel composites and provide critical insights to inspire researchers in future.

Structural colors, derived from existing natural creatures, have aroused widespread attention in the materials regulation for different applications. Here, inspired by the color adjusting mechanism of hummingbird, we present a novel shape-memory structural color hydrogel film by introducing shape memory polymers (SMPs) into synthetic inverse opal scaffold structure. The excellent flexibility as well as the inverse opal structure of the hydrogel films imparts them with stable stretchability and brilliant structural colors. Benefiting from the transient structural anisotropy of copolymers, the hybrid films are possessed with shape-morphing behaviors capability. Based on the shape transformations and color responsiveness performance, we have demonstrated diverse structural color actuators with complex shapes for different tasks. Notably, as the photothermal responsive graphene quantum dots were integrated into the hydrogel, the hybrid films could also be endowed with the feature of light-controlled reversible deformation with synchronous structural color variation. These features demonstrate that the presented shape-memory structural color hydrogel film is valuable for soft robotics with multi-functions of sensing, communication and disguise.

In recent years, the use of quantum dots (QDs) cocatalysts to improve the hydrogen evolution activity from the water splitting of photocatalysts has become a popular research topic. Herein, we successfully prepared a novel 0 dimension/2 dimension (0D/2D) heterojunction nanocomposite (denoted Ag2S quantum dots (QDs)/g-C3N4) with excellent photocatalytic performance by anchoring the Ag2S QDs cocatalyst on the surface of g-C3N4 through a self-assembly strategy. Ag2S QDs with an average particle size of approximately 5.8 nm were uniformly and tightly modified on g-C3N4. The Ag2S QDs/g-C3N4 composite with 0.5 wt% Ag2S QDs loading achieved the highest hydrogen evolution rate of 471.1 μmol·g−1·h−1 with an apparent quantum efficiency (AQE) of 1.48% at 405 nm. Such remarkable hydrogen evolution activity far exceeded that of undoped g-C3N4 and Ag2S nanoparticles (NPs)/g-C3N4. Moreover, it was 2.04 times the activity of Pt/g-C3N4 with Pt as the cocatalyst. The enhanced photocatalytic performance was attributed to the energy band broadening of Ag2S QDs caused by the quantum size effect and the convenient and effective charge transfer between g-C3N4 and Ag2S QDs cocatalysts. The mechanism underlying the enhanced photocatalytic H2 evolution activity was further proposed. This study demonstrates that semiconductor-based quantum dots are strong candidates for excellent cocatalysts in photocatalysis.

The recombination of charge carriers arriving from the random charge movement in semiconductor photocatalysts greatly limits the practical application of solar-driven H2 evolution. The design of photocatalytic systems with spatially oriented charge-transfer is a promising route to achieve high charge-separation efficiency for photocatalysts. Herein, novel sea-urchin-like ReS2 nanosheet/TiO2 nanoparticle heterojunctions (SURTHs) are constructed. The unique sea-urchin-like structure endows the ReS2 cocatalyst with an unusual charge edge-collection effect, which leads to a significant acceleration of charge separation and transfer, as evidenced by the well-designed selective photodeposition of Pt quantum dots in SURTHs. The markedly improved charge transfer capacity contributes to a high photocatalytic H2 evolution rate of 3.71 mmol h−1 g−1 for SURTHs (an apparent quantum efficiency (AQE) of 16.09%), up to 231.9 times by contrast with that of P25 TiO2. This work would provide a new platform for designing the high-efficiency cocatalyst/photocatalyst system with excellent charge transfer capacity. This work was funded by the China Postdoctoral Science Foundation (pre-station, No. 2019TQ0050), Applied Basic Research Program of Sichuan Province (No. 2020YJ0068), the China Postdoctoral Science Foundation (No. 2020M673186), National Natural Science Foundation of China (No. 22002014), the Applied Basic Research Program of Sichuan Province (No. 2020ZYD014). Thanks for the technical help from Sichuan Province Key Laboratory of Display Science and Technology, State Key Laboratory of Electronic Thin Films and Integrated Devices. Dr. Xiao Luo acknowledges financial support from the National Natural Science Foundation of China (No. 21903084) and Applied Basic Research Program of Sichuan Province (No. 2021YJ0408). Dr. Qing Liu acknowledges financial support from the National Natural Science Foundation of China (No. 52002051) and the Fundamental Research Funds for the Central Universities, SCUT (No. ZYGX2020J009).

In the work, CdSxSe1-x/N-GQDs composites were fabricated via a simple one-step hydrothermal process and their tunable composition, structure and photoelectric properties were characterized by various techniques. The photoelectric properties of CdSxSe1-x/N-GQDs could be adjusted by different Se/S ratios and tunable band-gaps. CdSxSe1-x/N-GQDs composites reached the optimal photocurrent response and the lowest interfacial impedance at the Se/S ratio of 0.75:0.25. Mott-Schottky plots and LSV spectra showed that the n-type CdS0.25Se0.75/N-GQDs presented a higher carrier density under light illumination. The excellent properties of the composites could be attributed to the mechanism involved in the excitation and electron-transfer process. On one hand, the band-gap of CdS0.25Se0.75/N-GQDs was narrowed, and more electrons were excited by the lower band-gap energy to promote a superior electron separation and transportation. On the other hand, N-GQDs acted as charge carriers and conductive way providers for electron-transfer instead of electron-hole recombination in the composites.

Stannous chloride and thiourea are used as source materials to prepare SnO2 quantum dots in the aqueous solution by a facile hydrolysis-oxidation process. The quantum dots have an average size of 1.9 nm with good dispersibility as well as long-term stability, and are validated to be an effective photocatalyst for the degradation of organic oil pollutants in contaminated water. The pollutant is removed by the quantum dots exposed to ultraviolet-visible irradiation at room temperature. The optimized condition is concluded to be a solution with quantum dot concentration of 10-3 mol/L and the degradation speed reaches the maximum at the 12 th hour after irradiation. After 48 hours, 91.9 % of octane is removed, concluding a high degradation efficiency. The prepared SnO2 quantum dots are potentially applicable in the remediation of marine environment as they hold the advantages of high efficiency, low cost and being environmental-friendly. The promotion and inhibition mechanisms of the photocatalytic SnO2 QDs at low and high concentrations are discussed.

This work mainly concentrated on the structural and optical properties of TiO2-doped transparent glass-ceramics embedding ZnO quantum dots (QDs). The results show that the concentration of non-bridging oxygen and related defects in the glasses increases and thermal parameters decreases by the introduction of TiO2. The surface defect concentration of ZnO QDs is greatly improved and the size of ZnO QDs is reduced by heat treatment below the Tg and the introduction of TiO2. The green emission of glasses is mainly derived from oxygen vacancy defects and the yellow emission of glass-ceramics primarily originated from oxygen interstitial defects which show a tendency of enhancing first and then reducing with the increase of TiO2 content. Among them, the optimal content for the strongest emission intensity of TiO2-doped glasses and glass-ceramics was determined to be 1.0 mol%, and the relative exceeds 10 times and 5.4 times that of TiO2-free glasses and glass-ceramics, respectively. The average size of ZnO QDs (∼2.1 nm) remarkably close to its exciton Bohr radius is successfully prepared by the optimal heat treatment condition (630 °C/8 h, below the Tg). The results show that these glass-ceramics embedding ZnO QDs are good yellow emission materials and have application prospects in WLEDs.

We demonstrated the sensing properties and adsorption mechanism of NO2 molecules of monolayer graphene and multilayer graphene encapsulated ZnO QDs for NO2 gas adsorption. The gas response value of ZnO-multilayer graphene (ZMLG) QDs was approximately 23 % and 7.2 and 25.5 times higher than that with ZnO-monolayer graphene (ZG) and ZnO QDs, respectively. The surface potential change of ZMLG QDs increased up to 14.25 times compared to ZnO QDs and 6.33 times increased compared to ZG QDs. We proposed an accurate adsorption mechanism for the improvement of the detection behavior that is occured by covering the graphene shells into ZnO QDs by the Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), and SKPM measurement. These results are expected to increase the accuracy of gas sensor characteristic analysis.

All-inorganic perovskite quantum dots have been widely used in solar cells, LED, laser and scintillator in recent years. However, the essence of ion migration in perovskite lattice can cause the ion vacancies exist, which can directly affect the luminescence process. Herein, we focus on the effect of monovalent cation vacancies on the CsPbBr3 lattice, and realize the adjusting lattice structure of the CsPbBr3 QDs to change the luminescence lifetime by controlling the formation of monovalent cation vacancies. The results show that the existence of monovalent cation vacancies can be controlled by controlling dosages of Cs + precursor and can make the CsPbBr3 lattice produce local lattice micro distortion and reduce luminescence lifetime, which is beneficial to realize the rapid and efficient X-ray imaging of scintillating crystals. Experimental result is also verified by density functional theory (DFT).

In this paper, a new method for pesticide detection based on porous silicon microcavities was proposed. First, the aptamer of acetamiprid was fixed in the functionalized porous silicon microcavity. Then, the complementary strand of the aptamer modified with graphene quantum dots was hybridized with the aptamer, and the effective refractive index of the porous silicon microcavity increased. When acetamiprid was added, it bound to the aptamer due to its stronger specificity. The aptamer separated from the complementary strand of the coupled graphene quantum dots and bound to acetamiprid, resulting in a decrease in the effective refractive index, and its central wavelength of reflection spectrum was blue shifted, and the blueshift increased with the increase of acetamiprid concentration. The relationship between the change in central wavelength and the concentration of acetamiprid was analysed, and the detection limit of acetamiprid was 151 nm.

CsPbBr3 quantum dots (CPB QDs) have great potential in photoreduction of CO2 to chemical fuels. However, the low charge transportation efficiency and chemical instability of CPB QDs presents a considerable challenge. Herein, we describe the electrostatic assemblies of negatively charged colloidal two dimensional (2D) Cu-Tetrakis(4-carboxyphenyl) porphyrins (Cu-TCPP) nanosheets and positively CPB QDs to construct the hydride heterojunction. The photogenerated electron migration from CPB QDs to Cu-TCPP nanosheets has been witnessed, providing the supply of long-lived electrons for the reduction of CO2 molecules adsorbed on Cu-TCPP matrix. As a direct result, The CPB@Cu-TCPP-x (x wt% of CPB QDs) photocatalysts exhibit significantly enhanced photocatalytic conversion of CO2, compared to the parent Cu-TCPP nanosheets or single CPB QDs. Especially, when with 20% CPB QDs, the heterostruture system achieves an evolution yield of 287.08 µmol g-1 in 4 h with highly CO selectivity (99%) under visible light irradiation, which is equivalent to a 3.87-fold improvement compared to the pristine CPB QDs. Meanwhile, the CH4 generation rate can be up to 3.25 µmol g-1. This optimized construction of heterostructure could provide a platform to funnel photoinduced electrons to the reaction center, which can both act as a crucial capture and the reaction actives of CO2.

Inhomogeneous Pb/Sn elemental distribution and the resulted phase segregation in mixed Pb-Sn halide perovskites would result in energy disorder (band structure and phase distribution disorder), which greatly limits their photovoltaic performance. Here, PbS quantum dot has been synthesized and demonstrated as seeds for modulation crystallization dynamics of the mixed Pb-Sn inorganic perovskites, allowing an enhanced film quality and significantly suppressing phase segregation. With this additive power conversion efficiency of 8% and 6% is obtained under irradiation of full sunlight in planar and mesoporous structured solar cells in combination with CsPb0.5Sn0.5I2Br inorganic perovskite, respectively. Our finding reveals exploring the actual Pb/Sn atoms location in perovskite structure and its influence on developing efficient and stable low-bandgap perovskite solar cells.

Carbon quantum dots (CQDs) are particularly sought after for their highly tailorable photoelectrochemical and optical properties. Simultaneously, graphitic carbon nitride (g-C3N4) has also gained widespread attention due to its suitable band gap energy as well as excellent chemical and thermal stabilities. Herein, a novel boron-doped CQD (BCQD) hybridized g-C3N4 homojunction (CN) nanocomposite was rationally engineered and fabricated via a facile hydrothermal route. The optimal photocatalyst sample, 1-BCQD/CN (with a 1:3 mass ratio of boron to CQD) accomplished a Rhodamine B (RhB) degradation efficiency of 97.0 % within 4 hours under low-powered LED light irradiation. The kinetic rate constant of 1.39 x 10-2 min-1 achieved by the optimum sample was found to be 3.6- and 2.8-folds higher than that of pristine CN and un-doped CQD/CN, respectively. Furthermore, 1-BCQD/CN demonstrated remarkable stability, where it retained close to 99.0% of its initial photocatalytic efficiency after three consecutive cycles. The marked improvement in photocatalytic performance of 1-BCQD/CN was attributed to several concomitant factors such as enhanced electron migration from CN to BCQD, suppressed electron-hole recombination and significantly higher charge density in facilitating charge migration. Based on the scavenging tests, it was revealed that the photogenerated holes (h+), superoxide anions (∙O2–) and hydroxyl radicals (∙OH) were the primary reactive species responsible for the photodegradation process. Overall, the highly efficient 1-BCQD/CN composite with excellent photocatalytic activity could provide a cost-effective and robust means for addressing the increasing concerns over global environmental pollution.

Deep-ultraviolet (Deep-UV) micro light-emitting diodes (Micro-LEDs) array greatly benefits various future applications. In this letter, we fabricated Deep-UV Micro-LEDs with different geometries from 10×10 µm2 to 200× 200 µm2, and investigated its application on tristimulus quantum dots converted display. As the Micro-LEDs scaling, the smaller-sized devices provided higher brightness under the same injection current density due to the enhanced current spreading uniformity and heat dissipation. For a 10×10 µm2 device, the maximal optical power density was up to 185 W/cm2 at 5 kA/cm2, and the peak external quantum efficiency reached 3.43 % at 30 A/cm2. The device exhibited a minor blue shift phenomenon as the current density increased. Deep-UV Micro-LED stimulated quantum dots display obtained 121% of the Rec. 2020 standard in the CIE 1931 color space. This ultra-wide color gamut indicated it as a competitive candidate for future display technology.

Exploring high-efficiency metal-free electrocatalysts towards N2 reduction reaction (NRR) is of great interest for the development of electrocatalytic N2 fixation technology. Herein, we combined boron nitride quantum dots (BNQDs) and graphitic carbon nitride (C3N4) to design a metal-free BNQDs/C3N4 heterostructure as an effective and durable NRR catalyst. The electronically coupled BNQDs/C3N4 presented an NH3 yield as high as 72.3 μg h−1 mg−1 (-0.3 V) and a Faradaic efficiency of 19.5% (-0.2 V), far superior to isolated BNQDs and C3N4, and outperforming nearly all previously reported metal-free catalysts. Theoretical computations unveiled that the N2 activation could be drastically enhanced at the BNQDs-C3N4 interface where interfacial BNQDs and C3N4 cooperatively adsorb N2 and stabilize *N2H intermediate, leading to the significantly promoted NRR process with an ultra-low overpotential of 0.23 V.

The urgent challenge of semiconductor photocatalysis technology is to prevent the rapid recombination of photogenerated electron-hole pairs on the basis of making full use of solar energy. Fortunately, the co-catalysts usually play a non-negligible role in achieving high photocatalytic performance. Herein, BN quantum dots (BNQDs) and Ag as novel dual co-catalysts are introduced on g-C3N4 (CN) nanosheets that could transfer carriers rapidly in a large area, boosting the photocatalytic performance of CN. Specifically, Ag is a bright choice for improving solar energy utilization and serving as electron sinks, while BNQDs could act as superior photoinduced-hole extractors. The photogenerated electron-hole pairs are finally pulled apart due to the synergistic effect of the dual co-catalysts, stimulating a large number of photogenerated electrons and holes to participate in their respective redox reactions efficiently. In consequence, the CN/Ag/BNQDs(3) ternary composites exhibit stronger oxidizing and reducing properties, which are reflected in the oxidative degradation efficiency of TC (80.54%) and the ability to reduce Cr(Ⅵ) (88.93%) within 60 min were 3.04 and 10.03 times than pure CN. This research paves a path for the design of photocatalysts with high-efficiency carrier separation capabilities, and broadens the way for the application of co-catalysts in the field of photocatalysis.

Nanostructured Bi2Te3 compounds have been synthesized by solvothermal method for thermoelectric applications. XRD results confirmed that synthesized materials have nano-dimension. This will increase phonon scattering. FESEM results revealed that synthesized materials have hexagonal plate like morphology. Manganese doping in nanostructured Bi2Te3 introduce defects and create density of interfaces. This can decrease the lattice thermal conductivity. As a result, Seebeck coefficient will increase due to quantum confinement cause due to nanostructuring. Thus, nanostructuring with doping is an efficient method to improve the ‘figure of merit’ of Bi2Te3 for thermoelectric applications.

Quantum confinement of the charge carriers of graphene is an effective way to engineer its properties. This is commonly realized through physical edges that are associated with the deterioration of mobility and strong suppression of plasmon resonances. Here, we demonstrate a simple, large-area, edge-free nanostructuring technique, based on amplifying random nanoscale structural corrugations to a level where they efficiently confine charge carriers, without inducing significant inter-valley scattering. This soft confinement allows the low-loss lateral ultra-confinement of graphene plasmons, scaling up their resonance frequency from the native terahertz to the commercially relevant visible range. Visible graphene plasmons localized into nanocorrugations mediate much stronger light–matter interactions (Raman enhancement) than previously achieved with graphene, enabling the detection of specific molecules from femtomolar solutions or ambient air. Moreover, nanocorrugated graphene sheets also support propagating visible plasmon modes, as revealed by scanning near-field optical microscopy observation of their interference patterns. A scalable soft nanoengineering technique enables the realization of visible plasmons in corrugated graphene.

Adequate light absorption and high carrier separation/transfer efficiency are central to elevate the development of highly efficient photocatalytic hydrogen evolution. Herein, a unique nano heterostructure is constructed by translocating 0D CdSe@(Zn, Cd)Se@ZnS quantum dots (CSS QDs) into the 3D hollow spherical graphite carbon nitride (SCN). The ultrafast TA spectroscopy and electrochemical measurements were measured to reveal the enhanced surface dependent electron transfer efficiency. Besides, the density functional theory (DFT) calculations further explained the mechanism of electrons transfer between interfaces. As expected, benefiting from the structural advantages of SCN and the channel-driven effectiveness produced by a step-accelerated system which is composed of (Zn, Cd)Se and ZnS double-shell layers of CSS QDs, the optimal hydrogen evolution rate of the prepared material in the photocatalytic hydrogen evolution reaction reached 132.5 μmol h−1, which was 7.6 times higher than that of the pure SCN under visible light irradiation. This work provides a novel avenue into the construction of nano heterostructure for solar hydrogen evolution.

Graphene quantum dots (GQD) have attracted much attention due to their unique properties in biomedical application, such as biosensing, imaging, and drug delivering. However, scale preparing red luminescing GQD is still challenging now. Herein, with the help of electron beam irradiation, a simple, rapid, and efficient up-to-down strategy was developed to synthesize GQD with size of 2.75 nm emitting 610 nm luminescence. GQD were further functionalized with polyethylene glycol (PEG) and exhibited good solubility and biocompatibility. The potential in vivo toxicity of PEGylated GQD could completely be eliminated by the clinic cholesterol-lowering drug simvastatin. PEGylated GQD could selectively accumulate in tumor after intravenous injection as a security, reliable and sensitive tumor fluorescence imaging agent. Therefore, this work presented a new method preparing red luminescing GQD for biomedical application.

Violet phosphorus quantum dots have been produced for the first time, which are effective fluorescent probes to selectively detect Cu2+. The morphology, microstructure and fluorescence properties have been tuned using synthesis parameters.

In the 21st century, revolutions in the renewable energy sector have been accelerating at a rapid pace. It is due to the search for environment-friendly sources of energy and to fit the modus operandi of a sustainable society intended for the well-being of future generations. The solar energy sector is witnessing several attempts to increase the efficacy of solar energy systems. The ongoing research in Quantum Dot Solar Cells (QDSC), Perovskites and Carbon nanotubes leads to the advancement in natural energy. The QDSCs are a fairly interesting concept that aims to increase the efficiencies and costs of the solar cell. In this paper, the construction and working of a Tandem Solar Cell is analysed and the different design parameters are calculated. The cell is a monolithic hybrid integrated structure consisting of a low bandgap Colloidal Quantum Dot (CQD) back cell on top of an Organic Photovoltaic (OPV) cell. The hybrid tandem solar cell is simulated using MATLAB software and the various parameters are calculated using various experimentations. Further, a Levenberg-Marquardt training algorithm is used to train the experimented parameters for hybrid tandem solar cells. The training algorithm has been successfully used to accurately predict values for short circuit current density using three input parameters namely the open-circuit voltage and the thicknesses of the OPV and CQD, respectively. The various experimentation using ANN show that the experimental values are relatively matched with predicted results.

Embedding all-inorganic cesium lead halide CsPbX3 (X=Cl, Br, I) perovskite quantum dots (PQDs) PQDs into glass is one of the most effective strategies to improve their optical, thermal and chemical stabilities. Herein, by using PbO instead of PbBr2 as the lead source, it is effective to lower the melting temperature and reduce the volatilization pollution from lead halide raw materials. Thus, a high-purity CsPbBr3 PQDs embedded glass with 71.5 % PLQY was successfully prepared. The thermal stability, and photo-aging properties were also improved. By simply changing the halogen element, the red and blue CsPbX3 PQDs embedded glasses were successfully prepared. The white LED fabricated by coating obtained green/red CsPbX3 PQDs embedded glass on a blue chip displays high color gamut of 121.9 % NTSC standard and >91.1 % Rec. 2020 standard, which embodies the great potential of PQDs embedded glass in lighting and display fields.