As-prepared Quantum Dots Research Articles

Exchange of Thiol Ligands on CuInS2 Quantum Dots in High Boiling Solvents.

As-prepared quantum dots are covered with long-chain ligands to prevent aggregation. When quantum dots are used in optoelectronic devices such as solar cells and QD-LED, ligand exchange is necessary to replace long-chain ligands with short-chain ones to increase the efficiency of charge transfer from the quantum dots to the electrode. In this study, we successfully exchanged 1-dodecanethiol (DDT) ligands on CuInS2 quantum dots with mercaptopropionic acid (MPA) ligands by using a two-phase system of high-boiling hydrophilic and hydrophobic solvents. The ligand exchange to MPA was achieved by using diethylene glycol (DEG) or ethylene glycol (EG) as the hydrophilic phase and tetradecane as the hydrophobic phase. The ligand exchange rate increased with increasing ligand exchange temperature. When quantum dot sensitized solar cells (QDSSCs) were fabricated using the ligand-exchanged quantum dots, a positive correlation was observed between the progress of ligand exchange and short-circuit current density. This is because charge transfer efficiency from the quantum dots to the TiO2 electrode was improved by the ligand exchange. This work has shown that QDs synthesized using DDT can be applied to optoelectronic devices.

Methotrexate-loaded manganese nitrogen dual-doped carbon quantum dots as targeted nano drug-delivery system for potential use in cancer theranostics

The present work highlights manganese nitrogen dual-doped carbon quantum dots as a novel pH-sensitive drug delivery system, for the delivery of methotrexate, targeted to cancer cells, along with the simultaneous real-time monitoring of cellular uptake and drug delivery using fluorescence imaging. Briefly, methotrexate was conjugated with the as-prepared quantum dots to form a nano drug-delivery system through non-covalent interactions. The developed material demonstrated drug loading efficiency of ∼91 % and a very efficient (∼80 %) pH-responsive drug release at pH 5.5. The cytotoxic properties of the developed nano-platform viz. manganese, nitrogen dual-doped carbon quantum dots, and methotrexate conjugated manganese nitrogen dual-doped carbon quantum dot complex were evaluated in cancer cells (HeLa) and healthy human cells (L929). The conjugated complex demonstrated excellent biocompatibility, high cellular uptake, and a substantial drug release. Healthy human cells were largely unaffected when incubated with both the MTX-conjugated Mn-, N-CQD and the free drug. Additionally, in vitro, the fluorescence bio-imaging potential of the developed nano-platform was also assessed, where the unconjugated (free) quantum dots exhibited better blue fluorescence imaging potential compared to that of the conjugated complex, which can be attributed to fluorescence quenching due to the presence of methotrexate. This study highlights the manganese nitrogen dual-doped carbon quantum dots capable of pH-responsive methotrexate drug delivery selective to cancer cells. The combination of drug delivery and fluorescence imaging creates an efficient platform for targeted therapy, allowing very precise drug release while accessing non-invasive monitoring of therapeutic response. This method holds a great promise for advancing cancer treatment strategies, with the potential for increased efficacy and decreased side effects.

Efficient fluorescence probe for detection of naproxen in pharmaceutical formulations and water samples using MPA-capped CdTe/ZnS core-shell nanocrystal-neutral red: Experimental and computational studies

The distinct optical properties of surface-engineered quantum dots, featuring high fluorescent quantum yields and biocompatibility, render them valuable tools for precise and selective sensing and biosensing applications spanning diverse fields, including medicine, environmental monitoring, and diagnostics. In this study, we have successfully fabricated a new “OFF-ON” fluorescent probe based on 3-mercaptopropionic acid (MPA) - capped CdTe/ZnS QDs and neutral red (NR) for the determination of Naproxen (NAP) in pharmaceutical formulations and water samples. The as-prepared MPA-TGA-CdTe/ZnS QDs exhibit a robust photoluminescent emission, peaking at 544 nm upon excitation with a 380 nm wavelength. The quantum yield measurement for the TGA-CdTe QDs was ascertained to be 29.3 %. The findings displayed that the fluorescence emission of MPA-TGA-CdTe/ZnS quantum dots (QDs) could be significantly quenched by increasing neutral red concentration, which can be attributed to the formation of non-fluorescent NR- MPA-TGA-CdTe/ZnS QDs complex (NR-MPA energy level 1.15 Kcal/mol). Upon the addition of naproxen, there was a noticeable enhancement in fluorescence intensity because of the formation of the strong complex between naproxen and NR (NR-NAP energy level: −1.54 Kcal/mol), leading to the detachment of NR from the surface of quantum dots. Consequently, the MPA-TGA-CdTe/ZnS QDs became activated, resulting in the restoration of fluorescence intensity of MPA-TGA-CdTe/ZnS QDs. The enhancement of fluorescence intensity exhibited a direct relationship with the concentration of naproxen, following a linear trend within the concentration range of 2.00 × 10−1 to 27.3 µmol/L with the detection limits of 7.0 × 10−2 µmol/L. Moreover, computational studies were also used to validate the MPA-TGA-CdTe/ZnS QDs turn-off-ON sensor for sensing naproxen. The interactions of NAP, NR, and MPA-TGA-CdTe/ZnS QDs made a solid base for controlling the fluorescent reversibility of QDs. The as-prepared quantum dots were subjected to cytotoxicity studies using an MTT assay and AAS technique. These findings revealed that MPA-TGA-CdTe/ZnS QDs have greater biocompatibility and lower toxicity, making them attractive for biological applications. The recoveries of naproxen detection using the proposed fluorescent probe in various pharmaceutical formulations and water samples ranged from 97.4 % to 102 %, with a relative standard deviation of less than 5 %.

Preparation of nanosheets embedded ZnSe/Bi2Se3 core/shell quantum dots for the study of optical properties and antibacterial activity

Cation exchange reaction is a well-known ion exchange method that is very much feasible for easy synthesis procedure and greater tunability in size and shape of nanomaterials. Here, we have synthesized different water dispersed ZnSe/Bi2Se3 core/shell quantum dots by using the cation exchange method with varying Bi content. The variation in Bi concentration allows the change in shell thickness which ultimately affects the structural and optical behaviors. The ZnSe/Bi2Se3 quantum dots exhibited type II band alignment. The as-prepared quantum dots embedded nanosheets exhibit broad, amorphous XRD pattern of the ZnSe phase. A shift in the peak position of the XRD pattern as well as Raman vibrational bands with varying Bi content suggests the formation of the Bi2Se3 shell. Also, the shifting among the XPS peaks confirms the change in the chemical environment of both Zn-Se and Bi-Se bonds in the hybrid system. This ensures the Se ions on the surface of ZnSe coordinated the bismuth complex. The increase in shell thickness enhances the band edge absorption and reduces the optical bandgap which is due to the increase in the particle size of the sample. A broad photoluminescence emission is observed for all the cases with 514 and 325 nm excitation. Each broad spectrum is comprised of different component peaks corresponding to excitonic and defects (vacancies and interstitials) related emission. The core/shell materials are most suitable for different biomedical applications. Hence, the ZnSe/Bi2Se3 quantum dots are analyzed for antibacterial activity, which showed a good antibacterial response against Staphylococcus aureus (ATCC 25,923).

Aqueous synthesis of 79% efficient AgInGaS/ZnS quantum dots for extremely high color rendering white light-emitting diodes

• The AgInGaS/ZnS QDs with an exceptional PL QY of 79% were successfully synthesized via microwave-assisted route, boosting the best performance of water-dispersible Ga containing I-III-VI QDs • Luminescent hydrogel films with different colors were obtained by embedding AgInGaS/ZnS QDs in PAAm/PVA hydrogel and a white LED based on the luminescent hydrogel films with a high color rendering index of 92.1 (R9=92.0) was obtained Over the past few decades, I-III-VI quantum dots (QDs) have attracted considerable attention due to their large Stokes shifts, good eco-friendliness, and wide tunable emissions. In this work, a facile microwave-assisted aqueous route using glutathione (GSH) and citric acid (CA) as dual stabilizers is introduced to synthesize AgInGaS/ZnS (AIGS/ZnS) core/shell QDs. An exceptional photoluminescence quantum yield (PL QY) as high as 79% is successfully achieved, boosting the best performance of water-dispersible AIGS QDs. By varying the Ag/Ga ratio, the PL peak wavelength can be tuned from 547 to 616 nm, and luminescent hydrogel films with different colors are obtained by embedding AIGS/ZnS QDs in polyacrylamide/ poly-vinyl alcohol (PAAm/PVA) hydrogels. The white light-emitting diode (WLED) with a high color rendering index (CRI) of 92.1 ( R 9 =92.0) and a correlated color temperature (CCT) of 3022 K is fabricated using QDs-PAAm/PVA hydrogel films in combination with a blue InGaN LED chip, indicating that the as-prepared QDs are competitive color-conversion materials for WLEDs.

Silver nanoparticles embedded sulfur doped graphitic carbon nitride quantum dots: A fluorescent nanosensor for detection of mercury ions in aqueous media

Graphitic carbon nitride (gCN) quantum dots, in recent years, have captivated enormous attention in the field of sensing due to their unique optical and electronic properties. We have reported a facile synthesis of silver nanoparticles (AgNPs) embedded sulfur-doped gCN quantum dots (Ag-S-gCN QDs) using thiourea, trisodium citrate, and silver nitrate precursors. The as-prepared quantum dots with an average particle size of 3.7 nm emitted strong blue fluorescence with a relative quantum yield of 36.5%. They exhibited significant stability against photobleaching and high ionic strength. The Ag-S-gCN QDs, under optimal conditions, were employed for fast sensing of Hg2+ ions in 3 min at pH 5. The limit of detection (LOD) and limit of quantification (LOQ) were measured to be 0.13 μM and 0.43 μM, respectively, with a linear range of 0.1–0.6 μM. The average lifetime of Ag-S-gCN QDs was calculated as 7.79 ns from a time-resolved decay experiment. A static quenching mechanism was proposed from the average lifetime calculation accompanied by a redox reaction via electron transfer from metallic Ag to Hg2+ ions. A substantial amount (>85%) of Hg2+ ions in the real water samples were recovered within a relative standard deviation (RSD) of ≤ 5%. The proposed nanosensor was anticipated to open up a new avenue for convenient, efficient, sensitive, and selective sensing of potentially hazardous Hg2+ ions.

N-doped graphene quantum dots for boosting the photoelectrochemical and photo-sensing properties of TiO2 nanorod array photoanodes

Nitrogen-doped graphene quantum dots (NGQDs) were successfully synthesized via a solvothermal technique using citric acid as carbon and N, N-dimethylformamide (DMF) acting as a solvent and also a nitrogen source. The as-prepared quantum dots have a diameter of less than 5 nm with a highly crystalline structure resembling graphene. TiO2 nanorods (NRs) were hydrothermally grown on fluorine-doped tin oxide (FTO) coated glass substrate. A photoanode of NGQD decorated TiO2 NRs was studied for its photoelectrochemical performance. Scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), and photoelectrochemical characterizations were performed to investigate the photoanode and its performance. The NGQD decorated TiO2 NR (NGQD/TiO2 NR) photoanode recorded an NGQD induced improvement of 36.7% in photocurrent density (at 5 V vs Ag/AgCl) and 58.7% in the photoconversion efficiency (η%).

Synthesis and optical properties of ultra-small Tin doped CsPbBr<sub>3</sub> blue luminescence quantum dots

All-inorganic perovskite CsPbX<sub>3</sub> (X = Cl, Br and I) quantum dots (QDs) have been wildly utilized in optoelectronic devices due to their tunable photoluminescence, high photoluminescence quantum yield (PLQY), and narrow-line width photoluminescence. However, the blue luminescence PLQY of CsPbX<sub>3</sub> perovskite quantum dots is still lower than their red and green luminescence counterparts (PLQYs nearly 100%). Here in this work, we present a handy strategy to synthesise the ultra-small blue luminescence Tin-doped CsPbBr<sub>3</sub> perovskite QDs by supersaturated recrystallization synthetic approach at room temperature, and the particle size of as-prepared QDs is lower than 4 nm. The crystal structure and optical property of Tin doped CsPbBr<sub>3</sub> QDs are characterized by XRD, TEM, ultraviolet-visible spectrophotometer, and fluorescence spectrophotometer. The results show that the particle size of as-prepared QDs is slightly shrunk from 3.33 nm (SnBr<sub>2</sub> 0.03 mmol) to 2.23 nm (SnBr<sub>2</sub> 0.06 mmol) as the SnBr<sub>2</sub> adding quantity increases, but there is no obvious change in the lattice spacing of doped QDs. The partial substitution of Pb for Tin leads the optical spectra to blue-shift from 490 nm (SnBr<sub>2</sub> 0.03 mmol) to 472 nm (SnBr<sub>2</sub> 0.06 mmol). The highest PLQY and the strongest XRD diffraction of ultra-small Tin doped CsPbBr<sub>3</sub>blue luminescence QDs are obtained by adding SnBr<sub>2</sub> 0.05 mmol, and the blue luminescence peak is located at 472 nm with the PLQY of 53.4%. There is no any change in PL peak of Tin doped CsPbBr<sub>3</sub> QDs (SnBr<sub>2</sub> 0.05 mmol) by storing it under the ambient atmosphere for 15 days, and the PLQY of Sn<sup>2+</sup> doped QDs is still 80% of the initial after 15 days. It is concluded that the crystallization and optical property can be effectively improved in Tin doped CsPbBr<sub>3</sub> QDs by partially replacing appropriate quantity of Pb by Tin.

Structural, optical and dielectric studies of wurtzite-type CdS quantum dots green synthesised using Ocimum sanctum (Tulsi) leaf extract

Present study reports the synthesis of CdS quantum dots (QDs) using Ocimum sanctum (Tulsi) leaf extract by green chemical method. The as-prepared QDs are characterised by different analytical methods. FTIR analysis indicates that the phytochemicals present in Tulsi leaf extract play an important role in controlling the size of the particle and its morphology. The structural properties and surface morphology studies are carried out by powder XRD and SEM with EDX. PXRD patterns revealed the hexagonal structure (wurtzite) for all CdS QDs. The average crystallite size lies in the range of 3.6–3.0 nm which decreases with the increase of the extract concentration. The lattice parameters of the pure and capped CdS QDs are found to be smaller than that of their bulk analogue. The EDAX study confirms the purity of all the prepared samples. The optical study is done by UV-vis spectroscopy and the particle sizes are estimated by an empirical method, which are in good agreement with those obtained from PXRD analysis. Dielectric constant of the QDs is obtained at room temperature at different frequencies where the frequency dependence is pronounced at the lower frequencies. It is noted that the band gap of the capped CdS QDs systematically increases with the increase of the extract concentration whereas the particles size and dielectric constant of these samples decreases with the increasing amount of the extract.

Emission tuning of highly efficient quaternary Ag-Cu-Ga-Se/ZnSe quantum dots for white light-emitting diodes

With the blooming development of zero-dimensional nanomaterials, I-III-VI alloying quantum dots (QDs) with outstanding photoelectrical properties have emerged to attract much attention as promising environmentally-friendly substitutions for conventional binary Cd-based QDs. In this work, a facile one-pot method was introduced to synthesize unreported quaternary Ag-Cu-Ga-Se/ZnSe (ACGSe/ZnSe) QDs. A relatively high photoluminescence quantum yield (PL QY) of 71.9% and a tunable emission from 510 to 620 nm were successfully achieved. We explored the roles of alloying compositions in ACGSe/ZnSe QDs, inferring that increased Ag proportion would not only lower the Vdefect level which leads to the blue shift of emission, but also slow the ZnSe shelling process owing to the larger lattice distortion. At last, the white light-emitting diodes (WLEDs) were fabricated with ACGSe/ZnSe QDs as the conversion layer, indicating that the as-prepared QDs are a promising candidate for further applications.

Thio amino acids-modified manganese doped ZnS quantum dot probes for the photoluminescent sensing of hazardous nitro aromatics

Abstract A simple, cost effective and rapid fluorescent method for the detection of most hazardous nitro aromatic compound, picric acid using the sulfur containing amino acids functionalized ZnS-Mn2+ Quantum dots (QDs) has been developed. The sulfur containing amino acids such as L-Cysteine and L-Methionine with the –SH and –SCH3 group respectively were introduced on the QDs for the surface functionalization and stabilization. The optical properties and structural features of the as-prepared QDs have been characterized by absorption spectra, fluorescence spectra, TCSPC lifetime studies, X-Ray diffraction, FT- IR spectral studies, DLS and Zeta potential. The amino group present in L-Cysteine and L-Methionine at the surface of the ZnS-Mn2+ QDs will bind the picric acid through the strong acid-base pairing interaction and the fluorescent quenching is mainly due to the electron transfer from the QDs to the picrate anions. The sensing ability of the synthesized QDs was confirmed by UV–visible absorption and fluorescence spectroscopic studies. The XRD studies and the FT-IR spectra also confirm the formation of picrate anion on the surface of QDs which is responsible for the sensing action. Under the optimal conditions, the response of the L-Cysteine/L-Methionine capped QDs was linearly proportional to the concentration of picric acid ranging from 0 to 2.2X10−7 M with detection limit 2.7X10-8 M and 3.2X10-8 M respectively. The developed sensing system can detect picric acid as low as 10-12 M using both the amino acids functionalized QDs.

Aqueous synthesis of L-cysteine-modified cobalt-doped zinc selenide/zinc sulfide quantum dots with enhanced fluorescence

Cobalt-doped zinc selenide/zinc sulfide quantum dots have been successfully synthesized directly in aqueous solution by using L-cysteine as the modifier. The optical properties and structures of the as-prepared quantum dots have been characterized through transmission electron microscopy, X-ray powder diffraction, infrared spectrum, energy dispersive X-ray spectrum, ultraviolet-visible spectrum, and fluorescence spectrum. The results show that cobalt-doped zinc selenide/zinc sulfide quantum dots are spherical particles with a diameter around 2.8 nm, have good dispersity and have a cubic zinc blende structure. The effects of several synthesis conditions on the fluorescence properties of the as-prepared quantum dots are surveyed and the optimum synthesis conditions are found to be as follows: reaction solution pH of 10.0; molar ratio of L-cysteine to hydrogen selenide ions to zinc ions of 1.6:0.15:1; doping content of cobalt ions of 2%; molar ratio of shell (zinc sulfide) to core (cobalt-doped zinc selenide) of 1.5:1. The fluorescence quantum yield of the as-prepared quantum dots increases from 6.4% to 19% via doping with cobalt ions and the epitaxial growth of zinc sulfide shell. The L-cysteine modified on the surface of cobalt-doped zinc selenide/zinc sulfide quantum dots renders the quantum dots water-soluble and bioconjugation capable. The L-cysteine-modified cobalt-doped zinc selenide/zinc sulfide quantum dots will have potential applications in biological fluorescence analysis.

Carbon quantum dots from glucose oxidation as a highly competent anode material for lithium and sodium-ion batteries

Carbon quantum dots derived from the chemical oxidation of D-(+)-glucose have been efficiently synthesized in good yield using a simple and economically viable approach. Carbon quantum dots possess a quasi-spherical structure with facile storage and transport channels for lithium and sodium-ions. When applied as an anode for the lithium-ion battery, the as-prepared quantum dots demonstrate a superior and stable cycling performance after 500 cycles (864.9 mAh g−1 at 0.5 C) with capacity retention of 91.6%, and a good rate performance (340.2 mAh g−1 at 20 C). As a sodium-ion battery anode, the quantum dots present a specific capacity of 323.9 mAh g−1 at 0.5 C and capacity retention of 72.4% after 500 charge/discharge cycles, indicating an excellent cycling stability. A relatively moderate rate performance of 123.6 mAh g−1 is achieved at the 20 C rate. This study demonstrates the use of individual quantum dots as a potential electrode material for lithium-ion, and sodium-ion battery applications, and it will definitely result in the fabrication of new composite materials in the energy-storage field. The extreme downsizing to the quantum regime has led to the achievement of utmost properties that have been prescribed to the quantum effects, efficient ion diffusion, and the charge transfer.

A facile route for highly efficient color-tunable Cu-Ga-Se/ZnSe quantum dots

I-III-VI group “green” quantum dots (QDs) are receiving increasing attention in photoelectronic conversion applications. In this work, a facile one-pot route directly dissolving copper iodide, gallium acetylacetonate and selenium powder as precursors into a mixed solution of dodecanethiol, oleylamine (OLA) and octadecene was developed to synthesize Cu-Ga-Se/ZnSe (CGSe/ZnSe) core/shell QDs. The resulting CGSe/ZnSe QDs with a relatively high photoluminescence quantum yield (PL QY) of 77.73% can be obtained and the particle size control from 4.20 to 5.73 nm can be realized via the variation of OLA dosage. The tunable emission from 485 to 630 nm can be acquired by introducing sulfur ion into CGSe host materials (anionic alloying) and varying the Cu/Ga precursor molar ratio. Furthermore, the PL recombination process in CGSe/ZnSe QDs is discussed using the PL decay curve. The proposed one-pot synthesis route for highly efficient color-tunable CGSe/ZnSe QDs is facile, rapid and environmentally-friendly. The as-prepared QDs are promising candidates for the exploration of novel and efficient light-emitting diodes.

One-Step Synthesis of Fluorescent Boron Nitride Quantum Dots via a Hydrothermal Strategy Using Melamine as Nitrogen Source for the Detection of Ferric Ions

A facile and effective approach for the preparation of functionalized born nitride quantum dots (BNQDs) with blue fluorescence was explored by the hydrothermal treatment of the mixture of boric acid and melamine at 200 °C for 15 h. The as-prepared BNQDs were characterized by transmission electron microscopy (TEM), high-resolution TEM, atomic force microscopy, X-ray photoelectron spectroscopy, UV-vis spectroscopy, and fluorescence spectroscopy. The single layered BNQDs with the average size of 3 nm showed a blue light emission under the illumination of the UV light. The BNQDs could be easily dispersed in an aqueous medium and applied as fluorescent probes for selective detection of Fe3+ with remarkable selectivity and sensitivity (the lowest detection limit was 0.3 μM). The fluorescence fiber imaging demonstrated that the as-prepared quantum dots could be used as a valuable fluorchrome. Therefore, the BNQDs could be envisioned for potential applications in many fields such as biocompatible staining, fluorescent probes, and biological labeling.

Tunable emission and morphology control of the Cu-In-S/ZnS quantum dots with dual stabilizer via microwave-assisted aqueous synthesis

Multinary quantum dots (QDs), owing to the large degree of freedom in their structure and composition, have a wide tunability in their bandgap and show an increased indeterminacy and complexity in their optical properties. In this work, a facile microwave-assisted aqueous route using sodium citrate and thioglycolic acid (TGA) as dual stabilizer was utilized to synthesize Cu−In−S/ZnS (CIS/ZnS) core/shell QDs. The effects of the shell thickness, refluxing time, pH value, temperature, Cu/In ratio and stabilizer on the morphology and optical properties of the CIS/ZnS QDs have been systematically investigated. The results show that the morphology-controllable alloyed CIS/ZnS QDs with tunable emission from 533 nm to 666 nm and long PL lifetime can be obtained by varying the molar ratio of sodium citrate to TGA. The proposed microwave-assisted aqueous synthesis method for alloyed QDs is simple, rapid, with comparatively low reaction temperature. The as-prepared QDs with the size of 3.8 nm are promising materials for lighting and biological applications.

Purple-, Blue-, and Green-Emitting Multishell Alloyed Quantum Dots: Synthesis, Characterization, and Application for Ratiometric Extracellular pH Sensing

We report the synthesis of a series of CdxZn1–xSe/CdyZn1–yS/ZnS and ZnSe/CdyZn1–yS/ZnS multishell alloyed luminescent semiconductor quantum dots (QDs) with fluorescence maxima ranging from 410 to 530 nm which cover the purple, blue, and green portion of the spectrum. Their subsequent surface modification to prepare water-soluble blue-emitting QDs, characterization, and application for ratiometric pH sensing in aqueous buffers and in an extracellular environment are further described. QDs were synthesized starting from ZnSe cores, and the fluorescence peak positions were tuned by (i) cation exchange with cadmium ions and/or (ii) overcoating with CdyZn1–yS layers. The as-prepared QDs had reasonably high fluorescence quantum yields (∼30–55%), narrow fluorescence bands (fwhm ∼25–35 nm), and monodispersed semispherical shapes. Ligand exchange with hydrophilic compact ligands was successfully carried out to prepare a series of water-soluble blue-emitting QDs. QDs coated with the hydrophilic compact ligands pres...

Room-Temperature Synthesis of Mn-Doped Cesium Lead Halide Quantum Dots with High Mn Substitution Ratio.

Here we report the room-temperature, atmospheric synthesis of Mn-doped cesium lead halide (CsPbX3) perovskite quantum dots (QDs). The synthesis is performed without any sort of protection, and the dual-color emission mechanism is revealed by density functional theory. The Mn concentration reaches a maximum atomic percentage of 37.73 at%, which is significantly higher in comparison to those achieved in earlier reports via high temperature hot injection method. The optical properties of as-prepared nanocrystals (NCs) remain consistent even after several months. Therefore, red-orange LEDs were fabricated by coating the composite of PS and as-prepared QDs onto ultraviolet LED chips. Additionally, the present approach may open up new methods for doping other ions in CsPbX3 QDs under room temperature, the capability of which is essential for applications such as memristors and other devices.

Fluorescence enhancement of glutathione capped CdTe/ZnS quantum dots by embedding into cationic starch for sensitive detection of rifampicin

In this study, we describe the synthesis of a new quantum dots (QDs) by embedding glutathione capped CdTe/ZnS QDs into cationic starch biopolymer (CS-GSH-CdTe/ZnS QDs). The fluorescence intensity of prepared QDs was significantly enhanced. When QDs interacted with rifampicin, the fluorescence intensity of the CS-GSH-CdTe/ZnS QDs was highly quenched compared with GSH-CdTe/ZnS QDs. Based on the above, a new fluorescent nanosensor for simple, sensitive and selective detection of rifampicin was developed. The fluorescence quenching was well described by the typical Stern–Volmer equation. After optimization, the linear range of the as-prepared QDs fluorescence intensity versus the concentration of rifampicin was F0/F=0.0422Q+1.109 (R2=0.99). The detection limit was 0.06×10−6mol/L. The proposed method with satisfactory results was used to detect rifampicin in commercial capsules and tablets.

Metal sulfide precursor aqueous solutions for fabrication of Ag-doped ZnxCd1−xS quantum dots thin films

Aqueous solution deposition of metal chalcogenide semiconductor thin films is considered a green and low-cost approach. So it is hard to find a general aqueous solution approach to deposit various kinds of high-quality metal sulfide quantum dots thin films. Here, we describe a green and robust aqueous solution approach, and five types of metal sulfide precursor solutions (Cu(CH3COO)2, AgNO3, Zn(CH3COO)2, Cd(CH3COO)2·2H2O, Ni(CH3COO)2·4H2O) can be prepared at room temperature under air atmosphere. By this green route, luminescent Ag-doped ZnxCd1−xS semiconductor films have been successfully synthesized via a facile and green method in the open air at 260°C using precursors. NH3·H2O (28–30%) were used as solvent, and 3-mercaptopropionic acid was used as the capping agents. As-prepared quantum dot thin films exhibit a tunable emission covering the whole visible light region. The absolute photoluminescence quantum yields can reach as high as 24.6%, which have a high potential application in luminescent, transparent, and conductive thin films.