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Perovskite quantum dots (QDs) have shown attractive prospects in the field of visible photocatalysis, especially in the synthesis of high value‐added chemicals. However, under aerobic conditions, the stable operation of QD catalysts has been limited by the reactive oxygen species (ROS) generated by photoexcitation, especially superoxide species O2⋅−. Here, we propose a strategy of Ce3+ doping in perovskite QDs to guide superoxide species for photocatalytic oxidation reactions. In C(sp3)−H bond oxidation of hydrocarbons, superoxide species were rapidly generated and efficiently utilized on the surface of perovskite QDs, which achieves the stable operation of the catalytic system and obtains a high product conversion rate (15.3 mmol/g/h for benzaldehydes). The mechanism studies show that the strong Ce‐oxygen affinity accelerates the relaxation process of photoinduced exciton transfer to superoxide species and inhibits the radiative recombination pathway. This work provides a new idea of utilizing oxygen species on perovskite surface and broadens the design strategy of high‐performance QD photocatalysts. [ABSTRACT FROM AUTHOR]

Abstract: Single‐electron transistors (SETs) have been proposed as a future alternative to conventional Si‐based electronics. However, their practical applications are strongly limited because most SETs operate at cryogenic temperatures. In this work, room temperature operating SETs are successfully fabricated with the realization of a mechanical buckling–defined quantum dot within a suspended and strained single‐walled carbon nanotube. Clear Coulomb oscillations are observed at room temperature due to the Coulomb blockade effect. The Coulomb charging energy is calculated to be 160 meV, which substantially exceeds the thermal energy. At 10 K, the Coulomb staircases are observed in the current–voltage characteristics with an energy level separation ≈29 meV, confirming that the island behaves as a well‐defined quantum dot for the electrons. This device fabrication method may also help future investigations into the electromechanical properties of nanotube quantum systems. [ABSTRACT FROM AUTHOR]

In this work, we designed a simple and sensitive fluorescence probe for sequential detection of lysozyme and trypsin. Firstly, l-cysteine was chosen as a stabilizer to obtain l-cysteine-capped CdTe QDs. Lysozyme with positive charges can interact with l-cysteine capped CdTe quantum dots (QDs) via the special assembly between lysozyme and l-cysteine, resulting in the quenching of the fluorescence of CdTe QDs. Lysozyme can be hydrolyzed into small fragments in the presence of trypsin, and the interaction between l-cysteine-capped CdTe QDs and lysozyme would be inhibited, which could be used for trypsin quantification. There was a linear relationship between the fluorescence intensity of CdTe QDs and the lysozyme concentration in the range of 75–1000 ng mL−1 and another linear relationship between the fluorescence intensity of CdTe QDs and the logarithm of the trypsin concentration in the range of 10–500 ng mL−1. The detection limits were 28.33 ng mL−1 for lysozyme and 8.35 ng mL−1 for trypsin, respectively. The established method showed a good selectivity for lysozyme and trypsin detection. [ABSTRACT FROM AUTHOR]

In this paper, we prepared fluorescence-tunable water-soluble CdS quantum dots (QDs) with hexametaphosphate as stabilizers by a simple route. The prepared CdS QDs were utilized to detect calcium ion (Ca 2+ ) based on an obvious fluorescence enhancement of CdS QDs induced by Ca 2+ . The results demonstrated there was an excellent linear relationship between the fluorescence intensity of hexametaphosphate-capped CdS QDs and Ca 2+ concentration in the range from 10 μmol/L to 400 μ mol/L and the detection limit for Ca 2+ was 4 μmol/L. Furthermore, fluoride ions (F − ) can react with Ca 2+ to generate the insoluble calcium fluoride that would inhibit the Ca 2+ -induced fluorescence enhancement of CdS QDs. Therefore, the designed Ca 2+ -induced fluorescence enhancement system was also able to effectively detect fluoride. [ABSTRACT FROM AUTHOR]

In this study, we reported a simple and sensitive fluorescence nanosensor for rapid detection of amifostine and alkaline phosphatase (ALP). The novel nanosensor was based on the fluorescence “turn on-off” of CdS quantum dots (QDs). Firstly, Cd 2+ cation could react with S 2− anion to generate fluorescent CdS QDs in the presence of amifostine. The fluorescence (FL) intensity of amifostine-capped CdS QDs (Amifostine-CdS QDs) was increased with the increasing amounts of amifostine, and could be used for amifostine detection. However, amifostine could be converted to 2-(3-aminopropylamino) ethanethiol (WR1065) in the presence of ALP based on the dephosphorylation of ALP. Under the optimum conditions, the affinity of WR1065 to CdS QDs was weaker than that of amifostine. Therefore the new generation of WR1065-CdS QDs would reduce the FL intensity with the increase of ALP concentration, and the fluorescence of CdS QDs was turn off. The metabolic process of amifostine in the presence of alkaline phosphatase could be also studied via the change of FL intensity of CdS QDs. The present method was cost-effective, convenient, and does not require any complicated synthetic procedures. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we have developed a simple and rapid method for the detection of Pb2+ based on the DNA sequence capped CdS quantum dots (QDs). We utilized the designed guanine (G)-rich DNA sequence (PS2.M) as a coating reagent to synthesize the DNA-capped CdS QDs. The designed G-rich DNA sequence PS2.M can bind with hemin to form G-quadruplex/hemin complex with K+, accompanied by the fluorescence quenching of CdS QDs via the photoinduced electron transfer. Pb2+ can induce conformational changes in the G-quadruplex/hemin complex to release the hemin molecules, so the quenched fluorescence of CdS QDs could be recovered. Therefore, the new fluorescent analysis system could be applied for the detection of Pb2+ based on the label-free DNA sequence capped CdS QDs. [Copyright &y& Elsevier]

In this paper, we developed dopamine functionalized–CdTe quantum dots as fluorescence probes for the determination of l-histidine. Firstly, CdTe was covalently linked to dopamine to form a kind of fluorescence sensor with pyrocatechol structure on the surface. The photoluminescence intensity of CdTe–dopamine (QDs–DA) could be quenched by Ni2+ due to the strong coordination interaction between the pyrocatechol structure of QDs–DA and Ni2+. In the presence of l-histidine, Ni2+ preferred to bind with l-histidine due to high affinity of Ni2+ to l-histidine and the photoluminescence intensity of QDs–DA was recovered. The recovered photoluminescence intensity of QDs–DA was proportional to the concentration of l-histidine in the ranges of 1.0×10−6–1.0×10−4 molL−1 and the detection limit was 5.0×10−7 molL−1 respectively. The established method showed a good selectivity for l-histidine among other common amino acids, and it was applied for determination of l-histidine in human serum sample with satisfactory results. [ABSTRACT FROM AUTHOR]

We have developed a simple and efficient fluorescence detection system for lysozyme utilizing I–III–VI type Cu–In–S ternary quantum dots (CuInS2 QDs) as the probe. Water-soluble near-infrared CuInS2 QDs capped with 3-mercaptopropionic acid were directly synthesized by using a hydrothermal method. Poly(dimethyl diallyl ammonium chloride), as a cationic polyelectrolyte, could bind to 3-mercaptopropionic acid-capped CuInS2 QDs via electrostatic interactions that would lead to fluorescence quenching of CuInS2 QDs. And the addition of a lysozyme aptamer could effectively turn on the quenched fluorescence due to the stronger interaction between the cationic polyelectrolyte and negatively charged aptamer. The addition of lysozyme would result in fluorescence quenching of CuInS2 QDs again due to the specific binding between lysozyme and the lysozyme aptamer. Therefore, this label-free fluorescence system could be applied to selectively detect lysozyme. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cd2+ reacts with S2− to generate fluorescent CdS QDs with ATP. [•] ATP can be hydrolyzed by the enzymatic dephosphorylation of ALP. [•] Fluorescent CdS QDs could not be generated in the presence of ALP. [•] The analysis system was successfully applied to assay ATP and ALP. [ABSTRACT FROM AUTHOR]

Highlights: [•] The water-soluble CuInS2 QDs was functionalized with dopamine molecules. [•] The fluorescence of the dopamine functionalized CuInS2 QDs was sensitive to pH value changes. [•] Urea would release OH− to change the pH value with urase as the catalyst. [•] The dopamine functionalized CuInS2 QDs could be utilized as a fluorescence probe for urea. [ABSTRACT FROM AUTHOR]

Water-soluble CuInS quantum dots (QDs) stabilized with 3-mercaptopropionic acid were synthesized in aqueous solution and then coated with bovine serum albumin. The resulting particles display fluorescence with a peak at 680 nm that is effectively quenched by 1, 4-dihydro-nicotinamide adenine dinucleotide (NADH), but not by 1, 4-nicotinamide adenine dinucleotide (NAD). The enzyme lactate dehydrogenase catalyzes the reduction of pyruvate and dehydrogenation of lactic acid using NAD or NADH as a cosubstrate. The new QDs were applied to monitor the course of lactate dehydrogenase-catalyzed reaction of pyruvate by detecting NADH via its quenching effect. This resulted in a convenient and selective detection scheme for pyruvate. The detection limit is as low as 25 nM. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a novel near-infrared fluorescence probe for the determination of 2,4,6-trinitrophenol (TNP) was developed based on bovine serum albumin (BSA) coated CuInS2 quantum dot (QD). Water-soluble CuInS2 QDs were directly synthesized in aqueous solution with mercaptopropionic acid (MPA) as stablizers, and it was coated by BSA via an amide link interacting with carboxyl of the MPA-capped CuInS2 QDs. The obtained BSA coated CuInS2 QDs (BSA-CuInS2 QDs) can bind TNP in water via the acid–base pairing interaction between electron-rich amino groups of BSA and electron-deficient nitroaromatic rings, and leading the fluorescence quenching of BSA-CuInS2 QDs. The quenched fluorescence intensity of BSA-CuInS2 QDs was proportional to the concentration of TNP in the concentration ranges from 50nmol/L to 3.0μmol/L. The detection limit (LOD) for TNP was 28nmol/L. The developed fluorescence probe showed a excellent resistant to interference of metal ions such as K+, Na+, Zn2+, Cu2+, Hg2+, and Pb2+. The developed biosensor was applied to the determination of TNP in spiked water samples with satisfactory results. [Copyright &y& Elsevier]

A novel, rapid and highly sensitive fluorescence turn-on assay for the detection of biothiols (glutathione, and l-cysteine), histidine and threonine was developed. Water-soluble CuInS2 ternary quantum dots (QDs) capped by mercaptopropionic acid (MPA) were directly synthesized in aqueous solution, and then functionalized using tyrosine molecules to form tyrosine-functionalized CuInS2 QDs (T-CuInS2 QDs). The fluorescence of T-CuInS2 QDs would decrease in the presence of Cu2+ due to the coordination effect of phenolic hydroxyls of the tyrosine molecules. Subsequently, the addition of biothiols (glutathione and l-cysteine), histidine or threonine could turn on the fluorescence of the T-CuInS2 QDs–Cu2+ system due to their strong affinity for Cu2+. The proposed method was simple in design and fast in operation, and it was applied for the detection of glutathione, l-cysteine, histidine, and threonine in human serum samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Abstract: Water-soluble CuInS2 ternary quantum dots (QDs) capped by mercaptopropionic acid were directly synthesized in aqueous solution. Consequently, the CuInS2 QDs were covalently linked to 3-aminophenyl boronic acid molecules to form the 3-aminophenyl boronic acid-functionalized CuInS2 QDs (F-CuInS2 QDs). The F-CuInS2 QDs had a fairly symmetric fluorescence emission centered at 736nm that was in the near-infrared region (NIR). The F-CuInS2 QDs containing boronic acid functional groups were reactive toward vicinal diols to form five- or six-member cyclic esters in an alkaline aqueous solution. The reaction would cause the fluorescence quenching, which could be used as a fluorescence probe for the determination of dopamine (DA). This assay could also probe other vicinal diols such as catechol, pyrogallol, and gallate, based on the fluorescence quenching of the F-CuInS2 QDs, and this assay was nearly unaffected by other phenol compounds such as phenol, resorcinol, and hydroquinone without the vicinal diol structures. The developed F-CuInS2 QDs were applied to the detection of DA in human serum samples with satisfactory results. Therefore, this experment provided a simple and sensitve NIR fluorescence probe for the detection of DA, catechol, pyrogallol, and gallate. [Copyright &y& Elsevier]

In this paper, Mn:ZnSe/ZnS core/shell-doped quantum dots (d-dots) with 3-mercaptopropionic acid as the stabilizer are successfully synthesized through a simple one-pot synthesis procedure in aqueous solution. The average diameter of Mn:ZnSe/ZnS core/shell d-dots is about 2.9 nm, which is lager than that of Mn:ZnSe cores (about 1.9 nm). The optical features and structure of the obtained Mn:ZnSe/ZnS core/shell quantum dots have been characterized by UV-Vis and fluorescence spectroscopy, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The photostability against UV irradiation and chemical stability against HO etching have been studied, and the results showed that the prepared Mn:ZnSe/ZnS core/shell d-dots are more stable than CdTe quantum dots prepared in aqueous solution. Finally, the resulting core/shell quantum dots are used as fluorescent label in human osteoblast-like HepG2 cell imaging. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a sensitive and simple method for the determination of melamine (MA) was developed based on the fluorescence changes of the water-soluble CuInS2 quantum dots (QDs). The water-soluble CuInS2 QDs capped by mercaptopropionic acid (MPA) was directly synthesized by hydrothermal method based on our previous report. The fluorescence emission of CuInS2 QDs was quenched by the oxidation of the surface of the QDs with H2O2, and the quenched fluorescence of CuInS2 QDs could be recovered upon the addition of small amounts of MA, which might be due to the surface passivation of the CuInS2 QDs by MA. The other amino acids such as glycine and lysine had no effect on the quenched fluorescence of CuInS2 QDs. Under optimum conditions, there was a good linear relationship between the fluorescence intensity of CuInS2 QDs and the concentration range of MA from 1.0×10−8 to 1.0×10−5 mol/L with a detection limit as low as 5nM. The proposed method was successfully applied to detect trace MA in raw milk with satisfactory results. Compared with previous reports, the proposed method manifested several advantages such as high sensitivity, short analysis time, low cost and ease of operation. [Copyright &y& Elsevier]

[Display omitted] 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 V defect 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. [ABSTRACT FROM AUTHOR]

A fluorescent suspension array combining digital encoding and molecular imprinting technologies was applied for multiplexed detection of phenols in aqueous medium. In this assay, nanomaterials such as silver (Ag), cuprous oxide (Cu 2 O), magnesium oxide (MgO), and zinc oxide (ZnO) were assembled on microbeads as digital encoding signal sources, then, (Digital encoding signal sources were produced by assembling silver (Ag), cuprous oxide Cu2O), magnesium oxide (MgO), and zinc oxide (ZnO) on microbeads. Molecular imprinted nanoparticles based on CdSe/ZnS quantum dots with various emission wavelengths (525, 565 and 585 nm) were grafted on the encoded beads through electrostatic adsorption and were used as the sensing units. The decoding spectra of the suspension array were stimulated and collected by a home-built laser induced breakdown spectroscopy system. The resulted spectra were transformed into digital sequences for encoding. As demonstrated in the gradient detections to various phenol solutions in concentration range of 0.98–62.5 μg/mL, the functionality of the suspension array was proven in the control experiments between the parent sensor beads and the molecular imprinting silica nanoparticles assembled sensor beads. Furthermore, the selectivity of suspension array was verified by the mixed adsorption experiments conducted in multicomponent analytes. [ABSTRACT FROM AUTHOR]

To achieve the dual-channel (analog and digital) encoding, microbeads assembled with quantum dots (QDs) and element coding nanoparticles (ECNPs) have been prepared. Dual-spectra, including fluorescence generated from quantum dots (QDs) and laser induced breakdown spectrum obtained from the plasma of ECNPs, including AgO, MgO and ZnO nanoparticles, has been adopted to provide more encoding amounts and more accurate dual recognition for encoded microbeads in multiplexed utilization. The experimental results demonstrate that the single microbead can be decoded in two optical channels. Multiplexed analysis and contrast adsorption experiment of anti-IgG verified the availability and specificity of dual-channel-coded microbeads in bioanalysis. In gradient detection of anti-IgG, we obtained the linear concentration response to target biomolecules from 3.125 × 10 −10  M to 1 × 10 −8  M, and the limit of detection was calculated to be 2.91 × 10 −11  M. [ABSTRACT FROM AUTHOR]