A serial of Ge quantum dot samples were grown by ion beam sputtering on Si(100) substrate at different temperature. The surface morphology and structure were studied with AFM and Raman spectra，Our results indicated that with temperature increasing，the density of quantum dots increased(At temperature of 750 ℃，the density of the quantum dots was up to 1.85×1010 cm-2)，the distribution of the quantum dots became more ordered，and the crystallinity became better. But the alloying processing was enhanced at the same time.

Abstract: CdTe/PEDOT-PSS microspheres are fabricated by in-situ seed polymerization. The morphology, structure, optical absorption and emission properties are characterized by using SEM FT-IR, XPS, Uv-vis and fluorescent spectra. The results suggest that the CdTe/ PEDOT-PSS hybrids synthesized by seed polymerization exhibit uniform microsphere structure. The absorption spectrum for hybrids is the sum of the spectra of two components, and the peak at 550nm in emission spectrum is a result of charge transfer, which indicates the potential application of the microspheres optoelectronic and photovoltaic devices.

Abstract: In this paper, we present a new procedure for the rapid synthesis of luminescent CdTe/CdSe core-shell quantum dots (QDs) in water phase by microwave irradiation method. The influences of microwave irradiation and a series of experimental variables, including heating temperature, molar ratios and concentration of precursors on the synthesis of QDs were investigated systematically. The results of high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) showed that the as-prepared nanocrystals had high crystallinity. In comparison with the plain CdTe QDs, both the photoluminescence quantum yield (PLQY) and photostability against UV irradiation of the CdTe/CdSe core-shell QDs have been greatly improved.

Ag colloids solution was synthesized by reduction of AgNO3 from sodium citrate. Monodisperse Ag nanoparticles films were self-assembled by electrostatic deposition technique. We investigated the optical properties of Ag nanoparticles. The size of Ag nanoparticles and its surface plasmon resonance absorption properties were controlled by changing the concentration of the reactants and the following annealing temperature. Ag nanoparticles mediated emission of CdSe quantum dots (QDs) was also studied. By coupled Ag nanoparticles film to CdSe QDs, a significant enhancement in photoluminescence (PL) intensity of CdSe QDs was observed, which was due to the enhancement effect of surface plasmon resonance from metal nanoparticles.

Abstract: Nanocrystalline TiO2 solution was prepared by hydro-thermal treatment at 230℃ with Titanium(Ⅳ) isopropoxide (C12H28O4Ti) as precursor solution. Anatase TiO2 nanocrystalline films with hierarchical structure were prepared on FTO glass substrates by electrohydrodynamic (EHD) technique and sintered at 450℃. CdS quantum dot sensitized nanocrystalline TiO2 heterostructure films were deposited by chemical bath method using the Cd(NO3)2 solution and Na2S solution as the reactants. The crystal structure, morphology and optical property of the film were investigated. The results indicate that nanocrystalline TiO2 films stack with the submicron spherical clusters, submicron and nanometer channels with wide dimension formed among the clusters which can facilitate the solution facilitation and ions adsorption. Nanocrystalline TiO2 heterostructure Films exist with CdS quantum dots with the range of 3-5nm. UV–vis absorbance spectra verified the blue shift of heterostructure Films due to the quantum confinement effects of quantum dots

Recently, the newly environmental friendly I-III-VI semiconductor quantum dots (QDs) AgInS2 has received significant progress by virtue of its excellent properties of quantum dots and the advantage of low-toxic. Therefore, it is expected to replace Cd-based quantum dots in various applications. Focus on the advances at home and abroad, the status and the existing problems of AgInS2 quantum dots are summerized and discussed. Furthermore, the prospects of the related research are presented.

GSH-stabilized high-luminescent CdTe quantum dots (QDs) were prepared using Na2TeO3 as the Te source by microwave irradiation in aqueous phase has been presented in this paper. The emission peak of CdTe QDs ranges from 515nm to 630nm and the high quantum yield reaches as high as 95%. The obtained CdTe QDs were characterized by X-ray diffraction pattern (XRD), high resolution transmission electron microscopy (HRTEM), UV-vis absorption and photoluminescence (PL) spectra. The two-photon absorption property of GSH-CdTe QDs was investigated using the two-photon excitation fluorescence measurement. In addition, human lung carcinoma cells (A549) were labeled using red-emitting GSH-CdTe QDs as a fluorescence probe by two-photon fluorescence imaging technique.

In this paper, ZnxCd1-xSe quantum dots with tunable photoluminescence emission, uniform particle size and good crystallinity were synthesized by hydrothermal method, in which N-acetyl-L-crysteine was used as a stabilizer. UV-vis absorption spectroscopy (UV-vis), photoluminescence (PL) spectroscopy, X-ray diffraction (XRD) spectroscopy, and high-resolution transmission electron microscopy were used to characterize their structures and properties. The effects of Cd2+/Zn2+ ratio, pH of the precursor solution, hydrothermal temperature and time on the photoluminescence properties of ZnxCd1-xSe quantum dots were significantly investigated in the present work. The results showed that the content of heavy metals in the quantum dots could be increased, which contribute to improving biocompatibility of the quantum dots. At the same time, the obtaining quantum dots possessed high photoluminescence yield (up to 35%) and narrow fluorescence full-width (FWHM<50nm). Therefore, the ZnxCd1-xSe quantum dots would be a promising fluorescent probe for biological and biomedical imaging.

Abstract Si/Si1-xNx multilayers were grown by alternating deposition of Si layer and Si1-xNx layer using magnetron sputtering and reactive magnetron sputtering under different N2 flows, and the post-deposition annealing of Si/Si1-xNx multilayers was performed. Transmission electron microscopy (TEM) was used to characterize the microstructure of multilayers. The cross-sectional TEM revealed that the formation of Si3N4 nanocrystallines for 2.5sccm N2 flows and Si nanocrystallines were embedded in Si layers and Si1-xNx layers of multilayers deposited under 5.0sccm N2 flows and in Si layers of multilayers deposited at 7.5sccm N2 flows.

A series of self-assembled Ge quantum dots (QDs) were grown on Si substrate by ion beam sputtering deposition technology. The effects of current density on the size and shape distribution of Ge/Si dots were studied. The measurement of atomic force microscope (AFM) showed that the dot density enhanced with current density increased. Meanwhile, the dome dots were transformed to transitional domes with the dot size decreased. The uniformity of size distribution became better at the current density of 0.86 mA?cm-2 compared with the standard deviation of dot diameter. The current density was proportional to the deposition rate of Ge, and it determined the ability to form nucleus from the encounter of ad-atom and other atoms.

Carbon quantum dots (CDs) are widely used in various fields due to their unique physical or chemical properties. Compared with traditional semiconductor quantum dots, the biggest advantages of CDs are low cytotoxicity, high biocompatibility, and at the same time being environmentally friendly. Obtaining carbon dots that meet the application conditions by selecting a specific synthesis or modification method is an urgent need for researchers. This paper reviews various top-down and bottom-up synthesis methods of CDs and describes their various properties after synthesis, in which the top-down method is biased towards producing a larger amount of Cdots, but the size and Cdots form is difficult to control. The bottom-up method can better control the size and shape of carbon dots, but the process is more complicated and time-consuming. The research progress of surface modification of CDs, including surface passivation and surface functionalization, was further discussed. Moreover, the characteristics of Cdots prepared by different synthesis methods or modification methods are quite different, extending their applications in various aspects, including cell imaging, fluorescence sensing, drug delivery, photocatalysis, ion detection, etc. Finally, we summarize and analyze the aspects of carbon dots that can be further explored, in order to provide references for more in-depth research and wider application of carbon dots.

Chiral carbon quantum dots have a wide application prospect in sensors, catalysis and biomedicine due to their excellent properties. They not only have chiral properties, but also inherit the excellent properties of carbon quantum dots including optical activity, photoluminescence, low toxicity and good biocompatibility. In this paper, it is summarized on the development process, the synthesis methods, and application research of chiral carbon quantum dots. And the prospect of the chiral carbon quantum dots are also prospected. It will provide reference for the related application research of chiral carbon dots in the future.

Mercaptosuccinic acid (MSA) -capped CdTe quantum dots (QDs) were prepared in an aqueous medium with CdCl2 and TeO2 as raw materials, and NaBH4 as reductant. The influence of refluxing time and tellurium to cadmium molar ratio on the luminescent properties of the obtained CdTe QDs were investigated, and the obtained QDs were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy and fluorescent spectroscopy, respectively. The results showed that the CdTe QDs were of zinc-blended crystal structure in a sphere-like shape. The absorption and fluorescence spectra of QDs shifted to longer wavelengths with the increasing of refluxing time. The CdTe QDs with the emission color ranging from green to red could be prepared at pH= 10.5, n (Cd ):n (Te ):n (MSA) = 1:0.05:1.4 within 5 h., the maximum quantum yield was 70.3 %.

The efficiency of the quantum dot sensitized solar cell have broken through 5% up to now. But there is a big distance between the efficiency of quantum dot sensitized solar cell with that of the dye sensitized solar cell which is 12%. Five points which are charge recombation, light harvesting, structure of photoanode, electrolyte and counter electrode were put forward as the reason for the low efficiency of the quantum dot sensitized solar cell. Meanwhile the solution to them by researchers in the field of quantum dot sensitized solar cell was also introduced.

Graphene-metal selenium quantum dots (QDs) composites have been prepared by ?-? stacking of pyridine-capped metal selenium QDs and chemically converted graphene (CCG) in aqueous solution. The aromatic structures of pyridine capped on metal selenium QDs introduce a ?-? stacking interaction between CCG and QDs, and extend the conjugated structure of CCG. The structural details and formation mechanism of the resultant graphene-metal selenium QDs composites are characterized by X-ray diffraction, UV-vis absorption, transmission electron microscope and Raman scattering studies. The CCG-metal selenium composites disperse stably in aqueous solution, allows them to be potentially used in biological tissues and further application. The cyclic voltammetry experimental result shows that the electrochemical performances of CCG-ZnSe are greatly improved than that of pure CCG, ZnSe powder.

Ternary CuInS quantum dots were synthesized by decomposition of precursor, and the effect of synthesis parameter on the morphology and optical properties of CuInS nanocrystals was investigated. It is found that the particle size and optical property of CuInS crystals could be affected by reaction time and temperature. With increasing reaction time, the CuInS nanocrystals grow larger, accompanied with appearance of rodlike crystals and red shift of the peak of the fluorescent emission spectra. With increasing reaction temperature, the nucleation rate and the growing rate of nanocrystals increase as well as the particle size, also the shape of nanocrystals can vary from single sphere to mixing of sphere and rod, and red shift of emission peak will happen as well. Analysis of X-ray photoelectron spectrometer shows that as-synthesized particles are nanocrystals. This work would build foundation for further manufacture of non-toxic quantum dots light-emitting devices (QLEDs).

Semiconductor nanocrystals have quantum size effect and unique optical properties, which can be widely used in optoelectronic devices, biomarkers, solar cells, photocatalysis and so on. Therefore, semiconductor nanocrystals have become a research hotspot of more and more researchers. However, among many application limitations, high-performance QDs materials (II-VI or IV-VI) usually contain highly toxic elements such as Cd or Pb. Large amount of preparation and use of such materials will not only do great harm to human body, but also cause environmental and ecological problems. So the design and development of QDs materials with low toxicity is one of the research frontiers at present. By controlling the reaction conditions, surface coating and doping, researchers can control the properties of InP materials, letting it be better used in various fields.

In this paper, due to the unique optical properties, water-soluble CdSe/CdS/ZnS multilayer core shell QDs/DADA with stable fluorescence property were synthesized based on ligand-exchange method between quantum dots and 1,12-Dodecanediamine(DADA), then were dissolved in aqueous solution of different pH values. The testing results showed that QDs/DADA solution has photoresponse to the pH value, which fluorescence intensities increased and subsequently decreased gradually with the enhangcement of pH values.

Abstract: A series of Ge quantum dot samples at different C-induced layer temperature are grown on n-Si(100) substrates by ion beam sputtering. Their morphology and structure are characterizated by using AFM and Raman spectra. Our results show that when the growth temperature of C layer increases from 600℃ to 700℃, the density of the quantum dots decreases to a minimum and the crystalline becomes worse;the Si composition increases in quantum dots at the same time. When the growth temperature of C layer increases from 700℃ to 800℃, the density of the quantum dots increases to a maximum and the crystalline turns to better; while the composition of Si in Ge quantum dots reduces.

Graphene quantum dots (GQDs) are considered to be one of the most promising nanomaterials in environmental chemistry, device application and biomedical fields because of the spectral tunable range of their photoluminescence and their stabilities. The investigation of photoluminescence mechanism, the design of fluorescence spectrum and the further development of controllable synthesis methods especially large-scale preparation remains to be challenging in the application of GQDs. In this paper, the GQDs preparation methods including Top-down method, Bottom-up method and surface modification are briefly introduced. The photoluminescence properties and characteristics of GQDs and other quantum dot materials were compared. The influence of quantum confinement effect and edge or surface states on the photoluminescence properties of GQDs is reviewed.

In recent years, due to the rapid development of economy, a large number of pollutants have been produced, causing extremely serious harm to the environment. Among them, waste water has affected human life and health through various channels, but has not been effectively solved. Carbon quantum dots (CQDs), as a new type of nanocarbon materials with unique fluorescence properties, have the characteristics of low cost and environmental friendliness, among which the low toxicity and fluorescence characteristics can be used in the field of wastewater treatment. Therefore, this paper first introduces the common preparation methods of carbon quantum dots, and summarizes their advantages and disadvantages. Secondly, the latest application of carbon quantum dots as a catalyst for the degradation of various pollutants in wastewater, the preparation of composite film for the adsorption of heavy metals and organic dyes in wastewater, and as a sensor for the monitoring of toxic ions in wastewater are introduced. Finally, the shortcomings of carbon quantum dots in wastewater treatment are summarized, and the opportunities and challenges that carbon quantum dots will face in the future are proposed.

Abstract: A novel technology was developed for the synthsis of thioglycolic acid(TGA)-capped CdTe quantum dots(QDs) while sodium tellurite was used as the tellurium source. The influence of the concentration of Cd2+ and Cd2+-TGA precursor holding time in room temperature on the photoluminescence(PL) and fluorescence quantum yield(QY) were systematically investigated. The obtained QDs were characterized by X-ray powder diffraction(XRD) and transmission electron microcopy(TEM). The results show that the CdTe QDs are of zinc-blended crystal structure in a sphere-like shape. The CdTe QDs with maximum quantum yiele of 48.4% with the condition of the Cd2+-TGA precursors were static for 50min in room temperature before backflow and the concentration of Cd2+ was 0.00067mol/L.

Multi-period vertically stacked InGaAs quantum dots were grown by molecular beam epitaxy in Stranski-Krastanov mode with interruption of source, the multilayered 2D-arrays In0.43Ga0.57As/GaAs(001) dots-in-a-well were obtained with tunable dimension and density. The epitaxy structure of sample is composed of 500nm GaAs buffer layer, multi-period stacked InGaAs quantum dots and 60 monolayer GaAs. The growth process was monitored real time with reflection high energy electron diffraction, the surface morphology of sample was scanned with scanning tunneling microscope after anneal.

Quantum dots (QDs) are semiconductor nanocrystals with a size of 1-10 nm, which have special optical, electrical, and magnetic properties. They have great prospects in the fields of quantitative analysis, biomedicine, and solar cells. Among them, copper indium sulfide (CuInS₂) ternary QDs which has stable fluorescence properties, is considered to be an ideal green non-toxic environmentally friendly fluorescent nanomaterial because it does not contain toxic heavy metal elements such as cadmium or lead. This article introduces the research progress of CuInS₂ ternary QDs in detail. Starting from the basic properties, its optical properties are expounded. The different synthesis methods of CuInS₂ ternary QDs in organic and aqueous phases, and how to enhance its water solubility and biocompatibility by surface modification of functional molecules for meeting the requirements of biomedical applications are introduced. At the same time, the research progress of CuInS₂ ternary QDs in the quantitative detection of biomolecules, in vitro cell imaging and in vivo bioimaging is summarized, and the problems to be solved in the development of this kind of materials are prospected.

CdSe,CdSe/ZnS and Eu doped QDs were synthesized in LSS system. The QDs were characterized by TEM, XRD , PL and EDX. The TEM results show that the QDs have uniform size and morphology . And the results of XRD show CdSe/ZnS QDs belong to hexagonal crystal system . The PL of the samples prove that the CdSe QDs coated with suitable thickness ZnS have a remarkable rise in Luminous efficiency and the FWHM(the full width half maximum) . And we analyzed this results. The CdSe QDs doped with Eu have a new emission peak.in red area, while the CdSe(Eu)/ZnS QDs do not. We also clarified the causes of this phenomenon .

Photocatalytic technology is an effective way to solve the two major problems of environmental problems and energy crisis. The development of efficient photocatalysts has become a research hotspot in this field. As new type of carbon nanomaterial, Carbon quantum dots (CQDs) have garnered much attention in the field of photocatalysis because of their unique up-conversion luminescence and excellent photogenerated electron transfer properties. In this paper, the mechanism of photocatalytic degradation of pollutants and the properties of carbon quantum dots was introduced, the research progress of photocatalytic degradation of organic pollutants in water by carbon quantum dots was reviewed with emphasis, followed by an outlook on their future and potential development.

With the aging of population and increasing in life expectancy, the incidence/mortality rate of cancer in our country has ranked first in the world. Although many therapy strategies have been proposed, such as photothermal therapy, immunotherapy, etc., chemotherapy is still the first choice for cancer treatment. However, severe side effects greatly limit the efficacy of chemotherapy. To solve this problem, people use nanocarriers to deliver chemotherapeutic drugs. Among all kinds of nanocarriers, non-heavy metal quantum dots (NHM-QDs) have attracted much attention in biomedicine field due to their special physical and chemical properties, such as easily-modified surface structures, high surface area and low toxicity. Here, we present a review of current development in non-heavy metal quantum dots, especially their applications for drug delivery, including carbon quantum dots (CQDs), graphene quantum dots (GQDs), black phosphorus quantum dots (BPQDs), ZnO quantum dots (ZnO QDs). We also discuss the challenges and prospects of NHM-QDs based materials in drug delivery field.

Abstract: Double-layers Ge/Si quantum dot samples were grown on Si(100) substrate by ion beam sputtering system. The influence of buried strain on the growth of islands on the upper layer was studied by varying the thickness of Si spacer-layer and Ge deposition. When the thickness of spacer-layer is thin, the results show that a reduction of wetting-layer thickness of islands on the upper layer. In addition, with increasing the thickness of Ge deposition, the growth of islands on the second layer is modulated. Increasing the thickness of spacer-layer, the growth of islands on the second layer follows the buried dots. The change of growth mode is explained by the non-uniform strain field induced by the buried islands and passing through the spacer-layer.

Carbon quantum dots (CQDs) and their surface amine modification were prepared in a autoclave, and TiO2 was produced in the hydrothermal conditions, then CQDs was incorporated intoTiO2.Fluorescence intensity of amino-functional CQDs was higher than original CQDs, while the fluorescence of composite catalysts was quenched under the same conditions, and absorption capacity was strengthened in visible solar wavelength range. Photocatalytic property of single CQDs and TiO2 were both weak, composite catalysts can accelerate the degradation of methylene blue (MB). Ammonia-capped CQDs and TiO2 composite catalyst can degrade MB completely in 15 minutes , and ethylenediamine-capped CQDs and TiO2 composite catalyst only need 10 minutes. This showed that the availability of visible light increased.

GSH-stabilized high-luminescent Zn1-xCdxTe quantum dots (QDs) were prepared by microwave irradiation method in aqueous phase presented. The obtained ternary QDs were characterized by X-ray diffraction pattern (XRD), high resolution transmission electron microscopy (HRTEM), UV-vis absorption and photoluminescence (PL) spectra. The effects of reaction time, Cd2+/Zn2+ feed ratio, reaction temperature, pH of the precursor solution on the PL properties of ternary QDs were investigated in the present work. The MTT assay method was used to evaluate the cytotoxicity of GSH-Zn1-xCdxTe ternary QDs. Furthermore, the obtained ternary QDs were conjugated with β-actin antibody as fluorescence probes for cellular labeling.

Using 3-Mercaptopropionic acid(MPA) as surface coated agent,Mn2+-doped water- soluble quantum dots of ZnS were synthesized by co-precipitation method.The effects of Mn2+ dopant and doping amount on microstructure, morphology and photoluminescence properties of the As-products were researched by X-ray diffraction, transmission electron microscopy, UV-visible absorption spectrometer,and fluorescence spectrophotometer.The results show that the products were irregular spherical cubic zinc blender ZnS with sizes around 9.7nm. Photoluminescence spectra analysis show that Mn2+-doped ZnS quantum dots appeared two emission peaks located at 587nm and 637nm which indicated ZnS surface emitting and Mn2+: 4T1-?6A1 level characteristic luminescence respectively.The synthesis mechanism of Mn2+-doped ZnS quantum dots was studied by infrared spectroscopy.

A set of hydrodynamic cavitation reactor is designed according to the principle of hydrodynamic cavitation. Carbon quantum dots (CQDs) are prepared with glucose and alanine as raw material assisted hydrodynamic cavitation in this paper. It is charactered by Fourier transform infrared spectroscopy , X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy, high resolution transmission electron microscopy，fluorescence spectrophotometer and UV - visible spectrophotometry photometer. Experimental results show that CQDs were successfully synthesized with batch production assisted hydrodynamic cavitation device. CQDs were of small particle size, good dispersion, uniform particle ,good water solubility， multiple exciting wavelength and high fluorescence intensity, were rich in nitrogen doping and functional groups in the surface .the initial method with adjusted reaction vessel laid a foundation to be applied in small batch laboratory，especially in industrialized batch production

In this paper, graphene quantum dots were synthesized by hydrothermal method, and the synthesized ones were also characterized. Prepared process was in details as following six steps: (1) preparing graphene oxide by employing the improved Hummers method; (2)reducing graphene oxide by sodium borohydride and sodiumcitrate; (3)preoxidizing grapheme with sulfuric and nitricacid;(4) expanding treatment;(5) treating the above product by hydrothermal method;(6) dialyzing the solution for seven days to obtain the graphene quantum dots. Ultraviolet spectrum, fluorescence spectral, as well as the electrochemical and electroluminescent analysis was employed to character the final product. The result showed that the synthesized graphene quantum dots had good ultraviolet and fluorescence response signals and stability of the cheniluminescence.

ZnO quantum dots with different Eu-doped concentrations (0, 0.05, 0.10 and 0.15 mol/L) were prepared based on hydrothermal and spin-coating methods. Photoanode films were prepared on the basis of Eu-doped ZnO quantum dots, and quantum dot sensitized solar cells were prepared as photoanodes. The effects of Eu-doped concentration on the morphology, crystal structure, spectral properties and photoelectric properties of ZnO films were studied. The results showed that Eu-doped ZnO nanorods prepared by hydrothermal method belong to hexagonal wurtzite structure. Eu-doped ZnO nanorods did not produce new products, but refined the diameter of ZnO nanorod array, with a diameter distribution of 45~60 nm and a height of about 1.2 μm. The orientation and uniformity of ZnO nanorods had been improved. Eu doping reduced the band gap width of ZnO, reduced the photoluminescence intensity of ZnO, and improved the separation ability of electron pairs. When the concentration of Eu doping was 0.10 mol/L, the minimum band gap width of ZnO was 3.09, and the photoluminescence intensity was the lowest. The doping of Eu improved the photoelectric performance of the quantum dot sensitized solar cell assembled based on ZnO as the counter electrode. When the concentration of Eu doping was 0.10 mol/L, the photoelectric conversion efficiency could reach 4.03%, the charge transfer impedance of the counter electrode was 1.38 Ω, the exchange current density of the counter electrode was 9.92 mA/cm², and the photoelectric performance was the best.

Due to the simple preparation,steady performance, high efficiency of fluorescence quantum conversion, low cost, and environmental friendliness, carbon quantum dots (CQDs) have received considerable attention. In this paper, the methods of preparing CQDs and their applications in metal ion detection were reviewed. Finally, the new insight and novel thought were provided for exploring new preparation methods and key techniques of environmental applications for CQDs.

Graphene quantum dots (GQDs) have attracted widespread attention in recent years. However, because of the heterogeneity of GDQs’ microstructure, research on the photoluminescence mechanism is still not clear. The microstructure of GDQs can be analyzed to the full range by modern analyzing techniques, which has important significances on the study of photoluminescence mechanism of GQDs. Herein, some general characterizing techniques were comparatively reviewed and the recent progress of advanced characterizing techniques, especially combined techniques in the research of GDQs’ microstructure and bio-imaging application was placed emphasis on. Moreover, some perspectives on characterizing techniques and research trends of GQDs were presented.

Silver based nanomaterials have excellent bactericidal potential and can be used as antibacterial agents. Therefore, it is of great significance to synthesize silver sulfide nanomaterials by a simple, environmentally friendly and economical method. In this paper, silver sulfide quantum dots are biosynthesized using silver nitrate and sodium sulfite as precursors, and their possible antibacterial properties are revealed. Meyerozyma sp., a heavy metal tolerant fungus screened from soil of Daqing Oilfield, is used. Silver sulfide (Ag₂S) quantum dots are biosynthesized by reducing silver nitrate and sodium sulfite. The synthesized silver sulfide (Ag₂S) quantum dots are characterized by UV-vis, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), inverted fluorescence microscope and scanning electron microscope (SEM). The antibacterial activity of silver sulfide (Ag₂S) quantum dots is studied by disk diffusion method and drop plate sterilization. The results show that the silver sulfide (Ag₂S) quantum dots synthesized by Meyerozyma sp. are monoclinic α -Ag₂S crystals with the highest absorption peak at 410 nm. With the increase of the concentration of silver sulfide quantum, the diameter of the inhibition zone increases, and the antibacterial activity against gram-negative bacteria and gram-positive bacteria increases. The inhibition rate of silver sulfide (Ag₂S) quantum dots against Pseudomonas aeruginosa and Escherichia coli reaches 100% at 30 min and 90 min respectively. The inhibition rate of bacillus was 99.9% within 2 h. The possible antibacterial mechanism of silver sulfide (Ag₂S) quantum dots against bacteria is analyzed by SEM. The results show that silver sulfide (Ag₂S) quantum dots inhibit and damage the cell surface of Gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa and Gram-positive bacillus, and show significant antibacterial activity, which may be due to the small particle size of silver sulfide (Ag₂S) quantum dots. It attaches to the surface of the cell membrane of bacteria, causing damage to the cell membrane, and penetrates the cell membrane, destroying the DNA and proteins therein and leading to cell death.

Abstract: Carbon quantum dots (CQDs, C-dots or CDs), a new type of carbon materials, less than 10 nm in size, have a lot of excellent performance, such as superior solubility in water, chemical inertness, low toxicity, easy functionalization, resistance to photobleaching and good photostability, having attracted widespread attention as a rising star in nanocarbon family in recent years. Since the phenomenon of bright colorful light from carbon quantum dots was reported in 2006, research groups around the world have begun to investigate the carbon quantum dots. CQDs produced from various synthetic strategies find their wide values in more and more fields, especially in biomedicine, optoeletronics, catalysis and sensors. In this review, we describe the recent progress in the field of CQDs, focusing on their synthetic methods, size control, modification strategies, photoelectric properties, luminescent mechanism, and applications in biomedicine, optoelectronics, catalysis and sensor issues.

Different thickness of InGaAs quantum dots were prepared through intermittent interruption growth(IIG) of As resource in molecular beam epitaxy (MBE) and the morphologies of them were studied and analyzed by reflection high energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). The results show that the uniformity of quantum dots was improved under intermittent interrupt growth and the morphologies of quantum dots were controlled by the growth temperature and the amount of material deposited. A larger amount of material deposited could lead to higher density and more uniformity of quantum dots could be attained at higher growth temperature in a special range. There were three obvious differences phases such as layer-by-layer growth, formation and self-ripen phases of quantum dot and two transition points which were Stranski-Krastanow (SK) and self-ripen transition in the process of growth of InGaAs quantum dots.

Zinc-based quantum dots have been widely used in analysis detection and biomarker due to their unique optical properties, low toxicity and good biocompatibility. Based on the research progress, in this paper, the synthesis methods and functionalized modifications, as well as the application of zinc-based quantum dots in the field of biochemical sensing were systematically described. The development trends and prospects of application of zinc-based quantum dots were also discussed in detail.