Surface Of QDs Research Articles

Microwave synthesis of molybdenum disulfide quantum dots and the application in bilirubin sensing.

Molybdenum disulfide quantum dots (MoS2 QDs) is a new type of graphite like nanomaterial, which exhibited well chemical stability, unique fluorescence characteristics, and excellent biocompatibility. The conventional hydrothermal synthesis of MoS2 generally requires a long-term reaction at high temperature and high pressure. Herein, we have developed a simple and fast MoS2 QDs synthesis scheme using microwave heating, and further modified the surface of MoS2 QDs using 3-aminophenylboronic acid. The 3- aminophenylboronic acid modified MoS2 QDs (B-MoS2 QDs) were further coated by a zinc-based metal-organic backbone (ZIF-8) in a solution containing zinc ions and 2-methylimidazolium. The constructed nanohybrid B-MoS2@ZIF-8 were successfully applied to the visualization and rapid detection of bilirubin based on the ratiometric fluorescence changes. The linear range for bilirubin detection is 0.2-75 μmol•L-1, and detection limit is 0.017 μmol•L-1.

Microwave synthesis of molybdenum disulfide quantum dots and the application in bilirubin sensing.

Molybdenum disulfide quantum dots (MoS2 QDs) is a new type of graphite like nanomaterial, which exhibited well chemical stability, unique fluorescence characteristics, and excellent biocompatibility. The conventional hydrothermal synthesis of MoS2 generally requires a long-term reaction at high temperature and high pressure. Herein, we have developed a simple and fast MoS2 QDs synthesis scheme using microwave heating, and further modified the surface of MoS2 QDs using 3-aminophenylboronic acid. The 3- aminophenylboronic acid modified MoS2 QDs (B-MoS2 QDs) were further coated by a zinc-based metal-organic backbone (ZIF-8) in a solution containing zinc ions and 2-methylimidazolium. The constructed nanohybrid B-MoS2@ZIF-8 were successfully applied to the visualization and rapid detection of bilirubin based on the ratiometric fluorescence changes. The linear range for bilirubin detection is 0.2-75 μmol•L-1, and detection limit is 0.017 μmol•L-1.

Ligand-Tuned AgBiS2 Planar Heterojunctions Enable Efficient Ultrathin Solar Cells.

AgBiS2 quantum dots (ABS QDs) have emerged as highly promising candidates for photovoltaic applications due to their strong sunlight absorption, nontoxicity, and elemental availability. Nevertheless, the efficiencies of ABS solar cells currently fall far short of their thermodynamic limits due in large part to sluggish charge transport characteristics in nanocrystal-derived films. In this study, we overcome this limitation by tuning the surfaces of ABS semiconductor QDs via a solvent-induced ligand exchange (SILE) strategy and provide key insights into the role of surface composition on both n- and p-type charge transfer doping, as well as long-range charge transport. Using this approach, the electronic properties of ABS films were systematically modulated, thereby enabling the design of planar p-n heterojunctions featuring favorable band alignment for solar cell applications. Carrier transport and separation are significantly enhanced by the built-in electric fields generated within the ultrathin (30 nm) ABS heterojunction absorber layers, resulting in a notable solar-cell power conversion efficiency of 7.43%. Overall, this study presents a systematic and straightforward strategy to tune not only the surfaces of ABS, but also the electronic properties of solid-state films, thereby enabling junction engineering for the development of advanced semiconductor structures tailored for photovoltaic applications.

Fluorescent Mn3O4 quantum dot as catechol oxidase nanozyme: A robust nano-platform for sensitive dopamine detection

The development of multifunctional semi-conductor nano-enzymes has attained significant interest recently, due to their ease in fabrication, cost-effectiveness, and wide range of applications. In this work, we report the synthesis of ammine-functionalized Mn3O4 quantum dots (Mn3O4 QDs) with excellent luminescence properties. These QDs have been developed via the reduction of permanganate using L-cysteine through a simple, facile one-step bottom-up approach. The steady-state enzyme kinetic studies revealed the superior Catechol-Oxidase mimic activity of the Mn3O4 QDs with a Michaelis-Menten constant (Km) of 133.19 µM, and maximum reaction velocity (Vmax) of 69.40 µMs−1. Due to this superior enzymatic activity, dopamine (DA) gets easily oxidized into DA-quinone and eventually polymerized to form polydopamine. Schiff base/Michael addition reaction between nucleophilic ammine on the surface of QDs and the aromatic chain makes the probe and analyte come closer and leads to the formation of a charge transfer complex, resulting in fluorescence quenching of QDs. This fluorescence quenching has been quantified to develop a turn-off sensor for DA. The sensing characteristics are highly selective and sensitive towards DA with a detection limit of 18 nM. The synthesised Mn3O4 QDs with superior enzyme-mimicking properties have tremendous potential as fluorescent probes in imaging and health care applications.

Iron oxide quantum dots‐based fluorescence probe for rapid and selective cytosine sensing

AbstractThe application of iron oxide quantum dots (IOQDs) in this study led to the development of a straightforward, easy, and selective approach for cytosine sensing. To examine the capability of IOQDs in detecting nucleobases, attempts have been made to gain insight into the characteristics of IOQDs, including UV/Vis spectroscopic analysis, infrared spectroscopy, fluorescence spectroscopy, transmission electron microscopy, and powder‐XRD. We introduced IOQDs with a mean particle size distribution of 5.71 ± 0.08 nm for detecting cytosine by harnessing a turn‐on fluorescence phenomenon. The fostering fluorescence response of IOQDs was triggered in the presence of cytosine. In comparison, the presence of other nucleobases did not further induce the fluorescence signal of IOQDs. It was concluded that the hydrogen bonding bridging the carboxylate and hydroxyl groups on the surface of QDs with the amine groups of cytosine results in the elevation of IOQDs fluorescence.

Construction Au/FAPbI3 Schottky Heterojunction towards a High-Speed Electron Transfer Channel for High-Performance Perovskite Quantum Dot Solar Cells.

Formamidinium lead triiodide quantum dot (FAPbI3 QD) exhibits substantial potential in solar cells due to its suitable band gap, extended carrier lifetime, and superior phase stability. However, despite great attempts toward reconfiguring the surface chemical environment of FAPbI3 QDs, achieving the optimal efficiency of charge carrier extraction and transfer in cells remains a challenge. To circumvent this problem, we selectively introduced Au/FAPbI3 Schottky heterojunctions by reducing Au+ to Au0 and subsequently anchoring them on the surface of FAPbI3 QDs, which acts as a light-harvesting layer and establishes high-speed electron transfer channels (Au dot ↔ Au dot). As a result, the champion photoelectric conversion efficiency of solar cells reached 13.68%, a significant improvement over 11.19% of that of FAPbI3-based solar cells. The enhancement is attributed to efficient and directed electron transfer as well as a more aligned energy level arrangement. This work constructed Au/FAPbI3 QD Schottky heterojunctions, providing a viable strategy to enhance QD electron coupling for high-performance optoelectronic applications.

Biodegradable MXene Quantum Dots with High Near-Infrared Photothermal Performance for Cancer Treatment.

Photothermal therapy (PTT) offers significant potential in cancer treatment due to its short, simple, and less harmful nature. However, obtaining a photothermal agent (PTA) with good photothermal performance and biocompatibility remains a challenge. MXenes, which are PTAs, have shown promising results in cancer treatment. This study presents the preparation of Ti3C2 MXene quantum dots (MXene QDs) using a simple hydrothermal and ultrasonic method and their use as a PTA for cancer treatment. Compared to conventional MXene QDs synthesized using only the hydrothermal method, the ultrasonic process increased the degree of oxidation on the surface of the MXene QDs. This resulted in the presence of more hydrophilic groups such as hydroxyl groups on the MXene QD surfaces, leading to excellent dispersion in the aqueous system and biocompatibility of the prepared MXene QDs without the need for surface modification. The MXene QDs showed great photothermal performance with a photothermal conversion efficiency of 62.5%, resulting in the highest photothermal conversion efficiency among similar materials reported thus far. Both in vitro and in vivo experiments have proved the potent tumor inhibitory effect of the MXene QD-mediated PTT, with minimal harm to mice. Therefore, these MXene QDs hold a significant promise for clinical applications.

Metal-Solvent Complex Formation at the Surface of InP Colloidal Quantum Dots.

The surface chemistry of colloidal semiconductor nanocrystals (QDs) profoundly influences their physical and chemical attributes. The insulating organic shell ensuring colloidal stability impedes charge transfer, thus limiting optoelectronic applications. Exchanging these ligands with shorter inorganic ones enhances charge mobility and stability, which is pivotal for using these materials as active layers for LEDs, photodetectors, and transistors. Among those, InP QDs also serve as a model for surface chemistry investigations. This study focuses on group III metal salts as inorganic ligands for InP QDs. We explored the ligand exchange mechanism when metal halide, nitrate, and perchlorate salts of group III (Al, In Ga), common Lewis acids, are used as ligands for the conductive inks. Moreover, we compared the exchange mechanism for two starting model systems: InP QDs capped with myristate and oleylamine as X- and L-type native organic ligands, respectively. We found that all metal halide, nitrate, and perchlorate salts dissolved in polar solvents (such as n-methylformamide, dimethylformamide, dimethyl sulfoxide, H2O) with various polarity formed metal-solvent complex cations [M(Solvent)6]3+ (e.g., [Al(MFA)6]3+, [Ga(MFA)6]3+, [In(MFA)6]3+), which passivated the surface of InP QDs after the removal of the initial organic ligand. All metal halide capped InP/[M(Solvent)6]3+ QDs show excellent colloidal stability in polar solvents with high dielectric constant even after 6 months in concentrations up to 74 mg/mL. Our findings demonstrate the dominance of dissociation-complexation mechanisms in polar solvents, ensuring colloidal stability. This comprehensive understanding of InP QD surface chemistry paves the way for exploring more complex QD systems such as InAs and InSb QDs.

Photonic Properties of Thin Films Composed of Gallium Nitride Quantum Dots Synthesized by Nonequilibrium Plasma Aerotaxy.

Gallium nitride quantum dots (GaN QDs) are a promising material for optoelectronics, but the synthesis of freestanding GaN QDs remains a challenge. To date, the size-dependent photonic properties of freestanding GaN QDs have not been reported. Here, we examine the photonic properties exhibited by thin films composed of GaN QDs synthesized by nonequilibrium plasma aerotaxy. Each film exhibited two photoluminescence peaks after exposure to ambient air. The first peak was in the ultraviolet spectral region, and the second peak was in the visible region. Both peak positions depended on the QD size. Our findings, supported by transient absorption spectroscopy experiments, suggest that conduction band to valence band recombination was the cause of the ultraviolet photoluminescence and that recombination between the conduction band and an acceptor level was the cause of visible photoluminescence. Furthermore, we show that coating the surface of fresh QDs with Al2O3 suppressed the visible region photoluminescence, corroborating the conclusion that the photoactive defect was caused by oxidation in air.

Influence of a dual-stabiliser formed by 3-morpholinoethanesulfonic and 3-mercaptopropionic acids on the photophysical, electrochemical and electrochemiluminescent properties of aqueous soluble CdSe quantum dots

In order to obtain an emitter nanoprobe for applications in aqueous solutions, we synthesised quantum dots of CdSe (CdSe QDs) in aqueous solutions, which were stabilised with 3-morpholinoethanesulfonic (MES) and 3-mercaptopropionic (MPA) acids. Comprehensive photophysical and electrochemical studies were carried out in order to determine the optimum MPA:MES ratio that produces the highest electrogenerated chemiluminescence (ECL) intensity. We found that the variation between the relationship of MPA and MES directly affected the surface, the size and properties of the CdSe QDs. Characteristic parameters of CdSe QDs were determined by conventional photophysical and electrochemical techniques, where an excellent correlation between the two methods was found. In addition, diameter, quantum yield (ϕNC), bandgap (Eg) and lifetime of CdSe QDs were determined. It was also observed that as the proportion of MPA in the capping increased, the ϕNC increased, and that an increase in the proportion of MES in the capping increased the intensity of ECL. The surface state of quantum dots is responsible for the difference in the behaviour between fluorescence and electrochemiluminescence properties. These results allowed us to infer that the choice of dual-stabiliser will depend on the applications of the resulting quantum dots as nanoprobe emitters.

Transmission Electron Microscopy Peeled Surface Defect of Perovskite Quantum Dots to Improve Crystal Structure.

Transmission electron microscopy (TEM) is an excellent characterization method to analyze the size, morphology, crystalline state, and microstructure of perovskite quantum dots (PeQDs). Nevertheless, the electron beam of TEM as an illumination source provides high energy, which causes morphological variation (fusion and melting) and recession of the crystalline structure in low radiolysis tolerance specimens. Hence, a novel and facile strategy is proposed: electron beam peel [PbBr6]4- octahedron defects from the surface of QDs to optimize the crystal structure. TEM and high-angle annular dark-field scanning TEM (HAADF) tests indicate that the [PbBr6]4- octahedron would be peeled from the surface of QDs when QDs samples were irradiated under high-power irradiation, and then a clear image would be obtained. To avoid interference from a protective film of "carbon deposits" on the surface of the sample when using high resolution TEM, amorphous carbon film (15-20 nm) was deposited on the surface of QDs film and then characterized by TEM and HAADF. The detection consequences showed that the defection of PbBr2 on the surface of QDs will gradually disappear with the extension of radiation time, which further verifies the conjecture.

A novel chemiluminescent probe based on the oxidase-like activity of pyrite quantum dots for the determination of copper in food samples

Pyrite (FeS2) quantum dots (PQDs) exhibit outstanding oxidase-like activity, which can be a ground to apply them in the chemiluminescence (CL) systems. Herein, we show that PQDs in combination with luminol as an efficient CL reagent, create a powerful sensing platform. These QDs effectively catalyze the luminol oxidation with dissolved O2, producing an intense CL signal. Copper ions, having a great affinity to sulfur atoms on the surface of PQDs, adsorb onto the surface of QDs and inhibit their catalytic action, and so, diminish the CL intensity. Utilizing this effect, luminol-O2-PQDs in alkaline medium was established as a sensitive probe to determine copper in the concentration range of 2.0 to 100 nM with LOD of 1.2 nM. The validation of the method was performed by analysis of NIST certified reference materials, and high correlation between obtained concentration and reported values was obtained. Furthermore, the probe was applied to the detection of copper in mushroom, sunflower seeds and flour samples and comparison of the results with those obtained from a standard method approved its accuracy. Luminol-PQDs CL probe is a simple, selective, sensitive and low-cost tool for determination of copper in nutrition sources.

Photoredox C[sbnd]H arylation of heteroarenes by high-efficiency bismuth quantum dots

Pnictogen bismuth (Bi) has attracted great attention in recent years due to its unique properties. However, few reports have focused on the liquid-phase chemical transformation so far. In this work, zero-dimensional bismuth quantum dots (0D Bi QDs) are, for the first time, introduced as a heterogeneous photoredox catalyst for direct CH arylation of heteroarenes under ambient conditions. Due to high structural stability and superior catalytic property, the as-synthesized Bi QDs exhibited excellent direct CH arylation of heteroarenes in moderate to good yields at a very low loading (only 0.8 wt%) under visible light with simple protocol, amenable gram-scale synthesis and good reusability. Radical trapping experiments demonstrated that the aryl radicals generated on the surface of QDs. Density functional theory calculation demonstrates that the Bi QDs display suitable adsorption energy and efficient charge transfer to largely promote the direct CH arylation. Such a unique transformation opens up new opportunities toward direct CH arylation for valuable organic transformation.

Evidence of formation of diluted magnetic semiconductor Sn1-xMnxTe quantum dots in glass matrix

In the current study, we work to acquire quantum dots from manganese-doped tin telluride (SnTe). Diluted Magnetic Semiconductor Sn1-xMnxTe QDs were successfully synthesized embedded in a glass matrix. Fusion and heat treatment time methods were used to form and grow the QDs. Transmission electron microscopy images showed that quantum dots with an average diameter of 5 nm formed in the glass matrix. The interplanar distances dhkl measured in TEM and the pattern observed in electron diffraction from the selected area confirms the SnTe semiconductor crystalline nature. Electron paramagnetic resonance spectra reveal six hyperfine lines for electronic transition +½ ↔ -½ resulting from Mn2+ ions in the crystal field. EPR spectra indicated Mn2+ ion incorporation in the core and surface of Sn1-xMnxTe QDs. The observed A1 and ETO phonon modes and the blueshift/cm−1 in the Raman spectrum provide strong evidence for symmetry breaking and net polarizability established with xMn2+ ion doping in Sn1-xMnxTe QDs.

83‐1: Improved performance of EL‐QD display through surface modified QDs and inorganic nanoink

We demonstrated the ligand exchange procedure on the InP base green QDs and Zn(Mg)O surface to improve of efficiency at EL‐QDs device. Performace of EL‐QDs device was imporved by control of electron mobility and chargen balance through ligand exchange in QDs surface. Moverover, we can prevented QD aggregation of EML throgh surface modification of electron transfer nanoparticles on inverted top emitting device.

Effect of Ag$$_{2}$$S/SiO$$_{2}$$ QDs surface structure on luminescence photostability

Effect of Ag$$_{2}$$S/SiO$$_{2}$$ QDs surface structure on luminescence photostability

Rapid ultrasensitive detection of methamphetamine based on the FRET mechanism between apta-nanobiosensor based on CdTe/ZnS quantum dots and DNA-conjugated Cy3 fluorophore: Forensic biological fluids

A novel Apta- nano biosensor (ANB) based on CdTe/ZnS QDs were designed and applied for ultrasensitive determination of methamphetamine (MA) as one most addictive psychoactive substance at 1 min. Different steps of ANB formation and MA detection were reported by fluorescence spectra. In short, in the first step, the water-soluble ANB was prepared by the ligand-exchange method using the replacement of thioglycolic acid (TGA) and glutathione (GSH) molecules at the surface of QDs with thiolated MA aptamer. This phenomenon increases QDs' fluorescence intensity. In the second step, the optimal amount of DNA-conjugated Cy3 fluorophore was gradually added to obtain the mixture. Based on the fluorescence resonance energy transfer (FRET) mechanism, energy transfer from QDs to Cy3 fluorophore led to the quenching of QDs and turning on the fluorophore. Finally, by titrating different amounts of MA into this system, the thiolated labeled aptamer tends to attach to the target (MA). The Cy3 fluorophore is separated from the QD surface, which leads to the quenching of QDs and fluorophore. This quenching of the ANB could be performed based on a kind of photo-induced electron transfer (PET) mechanism. The detection limit of MA is 4.15 ± 1.08 × 10−12 mol L−1 with a dynamic range from 1.38 ± 0.75 × 10−11 to 99.98 ± 1.03 × 10−8 mol L−1. ANB was applied to determining MA in forensic biological fluids and the obtained results were evaluated with LC-MS-MS with satisfactory results.

Regulated the ferromagnetism of In[formula omitted]O[formula omitted] quantum dots by non-stoichiometry compositions

Due to different versions of ferromagnetic origin, the magnetic properties of oxide diluted magnetic semiconductor (ODMS) cannot be accurately determined. We have systematically investigate the magnetic properties and electronic structure of In2O3 quantum dots (Qds) with non-stoichiometry ratio by first-principle method with band-structure calculations. For the sake of contrastive analysis, some models are proposed to passivate the surface dangling bonds by pseudo-hydrogen atoms. We find that: (i), dangling bonds of oxygen atoms on the surface of Qds can induce 6 μB magnetic moments due to imbalanced chemical proportion. Spin polarization energy of the structure is as low as −763 eV. (ii), internal cation vacancy can induce magnetic moment, while internal anionic vacancy or surface hanging bond passivated by pseudo-hydrogen atoms cannot produce magnetic moment; and (iii), it has broken the chemical balance ratio of doping cobalt atoms where the magnetic moment mainly local area in the cobalt atoms and a little are distributed on some special O atoms which binding with the Co atoms. All three kinds of above results indicate that the non-stoichiometry compositions play an special roles to effect the magnetic properties and electronic structure in In2O3 Qds.

Ultrasensitive and rapid detection of methamphetamine in forensic biological fluids using fluorescent apta-nanobiosensors based on CdTe quantum dots

Rapid and sensitive detection of illegal and addictive drugs in biological samples is essential in various organizations such as forensic medicine, diagnostic clinics, and anti-narcotics headquarters. Methamphetamine (MA) is the second most addictive psychoactive substance, which poses a major threat to global health. This study aimed to propose a novel apta-nano biosensor for ultrasensitive and fast detection of MA in biological fluids. The water-soluble apta-nano biosensor was prepared with the ligand-exchange method using the replacement of thioglycolic acid (TGA) molecules at the surface of QDs with thiolated MA aptamer. The fluorescence intensity of QDs was increased after modification with aptamer and then decreased by the addition of the target molecule (MA) due to the formation of the aptamer-MA complex. The apta-nano biosensor was used as an ultrasensitive and selective fluorescent sensor for the determination of MA with a linear range of 1.34 ± 0.25 × 10−10–1.24 ± 0.07 × 10−7 mol/L, and the detection limit 40.34 ± 1.05 × 10−12 mol/L. The fabricated apta-nano biosensor can be successfully applied for the determination of MA in forensic biological fluids (blood plasma and urine) with satisfactory analytical results. Also, obtained results were evaluated with liquid chromatography-tandem mass spectrometry (LC-MS-MS).

Influence of bridge structure manipulation on the electrochemical performance of π-conjugated molecule-bridged silicon quantum dot nanocomposite anode materials for lithium-ion batteries.

To assess the influence of bridge structure manipulation on the electrochemical performance of π-conjugated molecule-bridged silicon quantum dot (Si QD) nanocomposite (SQNC) anode materials, we prepared two types of SQNCs by Sonogashira cross-coupling and hydrosilylation reactions; one is SQNC-VPEPV, wherein the Si QDs are covalently bonded by vinylene (V)-phenylene (P)-ethynylene (E)-phenylene-vinylene, and the other is SQNC-VPV. By comparing the electrochemical performances of the SQNCs, including that of the previously reported SQNC-VPEPEPV, we found that the SQNC with the highest specific capacity varied depending on the applied current density; SQNC-VPEPV (1420 mA h g-1) > SQNC-VPV (779 mA h g-1) > SQNC-VPEPEPV(465 mA h g-1) at 800 mA g-1, and SQNC-VPV (529 mA h g-1) > SQNC-VPEPEPV (53 mA h g-1) > SQNC-VPEPV (7 mA h g-1) at 2000 mA g-1. To understand this result, we performed EIS and GITT measurements of the SQNCs. In the course of investigating the lithium-ion diffusion coefficient, charge/discharge kinetics, and electrochemical performance of the SQNC anode materials, we found that electronic conductivity is a key parameter for determining the electrochemical performance of the SQNC. Two probable causes for the unique behavior of the electrochemical performances of the SQNCs are anticipated: (i) the SQNC with predominant electronic conductivity is varied depending on the current density applied during the cell operation, and (ii) the degree of surface oxidation of the Si QDs in the SQNCs varies depending on the structures of the surface organic molecules of the Si QDs and the bridging molecules of the SQNCs. Therefore, differences in the amount of oxides (SiO2)/suboxides (SiOx) on the surface of Si QDs lead to significant differences in conductivity and electrochemical performance between the SQNCs.