AgInS2 Quantum Dots Research Articles

Ultrasensitive miRNA-let-7a detection based on AgInS2 quantum dots co-sensitization and CRISPR/Cas12a induced strand displacement reaction for signal amplification

The evolution of breast cancer is usually accompanied by abnormal expression of miRNA-let-7a. Sensitive gauging of miRNA-let-7a is crucial for breast cancer monitoring and prognosis. Herein, a novel photoelectrochemical (PEC) biosensor was served as miRNA-let-7a detection on the basis of the coupling of co-sensitization and CRISPR/Cas12a-mediated strand displacement amplification (SDA). In short, AgInS2 quantum dots (QDs), characterized by a wide visible light absorption range and a stable photocurrent response, have an obvious sensitizing effect on TiO2/Bi2MoO6. Under the condition of without miRNA-let-7a, the AgInS2 fixed DNA probe was located near the surface of the TiO2/Bi2MoO6 electrode, forming a co-sensitive structure. During the detection process, hairpin DNA2 (HP2) specifically recognized miRNA-let-7a through base complementary pairing, triggering the SDA reaction to convert massive double-stranded DNA (dsDNA). The dsDNA product then triggered CRISPR/Cas12a lateral cleavage activity, causing AgInS2-sensitized DNA to leave the electrode surface and the co-sensitization effect to disappear, further reducing the photocurrent. Using a dual effect for signal amplification, the biosensor platform had linear detection capability within the scope of 0.01–10 nM, and the detection limit was 3.35 pM. The biosensor which was fabricated effectively provided an excellent platform for the effective monitoring of various tumor biomarkers in clinical detection.

Microwave synthesis of composite of AgInS2 quantum dots and zeolitic imidazolate framework-8 for application in white light emitting diodes

Preparation of AgInS2 quantum dots (AIS QDs) with high photoluminescence quantum yield (PLQY) and thermal stability remains an important challenge. In this paper, AIS QDs were successfully introduced into zeolitic imidazolate framework-8 (ZIF-8) by microwave-assisted hydrothermal method. Due to the effective isolation of the ZIF-8, the AIS QDs avoid the concentration quenching when they were assembled into white light emitting diodes (WLEDs) devices as color conversion materials. More importantly, the generation of ZnS layer between the interfaces of AIS QDs and ZIF-8 can efficiently improve the optical performance of AIS QDs, resulting in the fluorescence lifetime extended to 470.05 ns. Meanwhile, the PLQY of AIS/ZIF-8 composite reached up 34.30 % when microwave hydrothermal heating at 120 °C for 60 min with AgIn/Zn=1/3, which was higher than that of the pristine AIS QDs as 25.30 %. Finally, the WLED devices were fabricated by combining AIS/ZIF-8 composite fluorescent powder with (Ba, Sr)Si2O2N2:Eu2+ phosphors and blue LED. At 20 mA, the AIS/ZIF-8 based WLED shows the luminous efficiency (LE) of 44.54 lm/W, correlated color temperature (CCT) of 4242 K and color rendering index (CRI) of 89.1. Moreover, the Commission International de L'Eclairage (CIE) was (0.36, 0.35), indicating the WLED emited warm white light. The present strategy aims at enhancing the optical performance of AIS QDs, which also may trigger the development of QDs-based WLED.

Water-soluble near-infrared AgInS2 quantum dots for Ca2+ detection and bioimaging

Calcium ions (Ca2+) are key players in intracellular signaling as second messengers and play a pivotal role in various physiological processes. In this study, near-infrared water-soluble AgInS2 quantum dots (AIS QDs) for Ca2+ detection were synthesized by a one-step hydrothermal method. The fluorescence quantum yield (PL QY) of the quantum dots was as high as 23.99 %. With low cytotoxicity and good fluorescence properties, as well as short reaction time, the ternary AIS QDs have excellent synthesis efficiency and quantum yield, which are advantageous for Ca2+ detection and bioimaging applications. The fluorescence quenching of the quantum dots showed a clear linear relationship with calcium ion concentration in the range of 0–250 μM (detection limit: 0.65 μM). Confocal imaging experiments demonstrate the excellent biofluorescence imaging capability of AIS QDs. By tuning the Ag/In molar ratio, AIS QDs can achieve fluorescence emission in the near-infrared wavelength band (620–700 nm), and the near-infrared fluorescence imaging has deeper tissue penetration, less tissue absorption and photodamage, and lower interference of spontaneous fluorescence, which further expands the potential of QDs for bioimaging applications.

Synthesis of AgInS2 quantum dots for metronidazole detection in eggs using a fluorescence-quenched probe

Metronidazole (MNZ) is a type of nitroimidazole antibiotic widely used in livestock feed. The extensive use, overuse, and misuse of MNZ have resulted in high levels of MNZ residues in animal products, posing serious health risks to people. Based on the effective fluorescence quenching capability of MNZ, a highly precise technique characterized by low-cost materials, low detection limit, and simple operational procedure was established to detect MNZ in eggs by modulating the fluorescence produced by AgInS2 quantum dots (AIS QDs). The performance of the prepared sample was outstanding as the linear range was 0.25–80.00 μg/mL with a detection limit (LOD) of 0.166 μg/mL and R2 = 0.9996, having an average recovery of MNZ in egg white ranged from 94.88 % to 102.39 %. This detection method has the advantages of a wide detection range, high sensitivity, high accuracy, excellent selectivity, and simple operability, and it can be used to detect MNZ in eggs after further study. The fluorescence quenching mechanism of AIS QDs by MNZ is speculated as a dynamic quenching mechanism of light-induced electron transfer.

Surface strategy design concerning entrapment of chalcogenide onto ETFE substrate and extension to the assembly of memristor

Consideration of semi-conductor quantum dots as the suitable band-gap materials has been an effective way to replace the traditional emissive species such as phosphors, lanthanide edifices or organic building blocks. However, very few reports have been performed for the employment of such chalcogenide dots in brain-excitation devices such as memristors. In this work, the colloidal synthesis for the preparation of AgInS2 quantum dots as well as its optical characteristic has been recorded. Further exploration has been focused on the improvement of resistance switching behavior and a layer of manganese dioxide has been covered onto ITO conductive glass by electrochemical deposition. Following step concerns the incorporation of AgInS2 and the toluene solution of PMMA and the PMMA@AgInS2@MnO2 hybrid layer with optimized uniformity and stability has been afforded. Moreover, such functional device has been used to simulate biological synaptic behavior, which will provide an innovative and efficient route for the development of artificial synaptic functions.

A ratiometric carbon dots/AgInS2 quantum dots sensing probe for the kinetic determination of histamine resorting to N-PLS chemometric model

Biogenic amines are compounds that play several crucial roles in the human body but can also cause serious health problems when present at high concentrations in foodstuffs. Therefore, it is important to develop rapid, simple, cost-effective, and reliable analytical techniques for their monitoring, acting as indicators of food quality and preventing potential risks. In this sense, carbon dots and 3-mercaptopropionic acid (MPA)-capped AgInS2 (AIS) quantum dots were used as fluorescent probes to implement a ratiometric sensing platform, coupled to chemometrics, for the kinetic fluorometric determination of histamine in foodstuffs using second-order data. The obtained data were analysed through unfolded partial least squares (U-PLS) and N-way partial least squares (N-PLS). The model optimization revealed that the application of N-PLS yielded the best results and that a kinetic spectral acquisition for 5 minutes was enough to ensure reliable measurements. The developed method was evaluated using spiked samples of different complex matrices (tuna, tomato and hake fish), at different concentration levels, and the obtained results, in terms of figures of merit, confirmed its suitability, accuracy and effectiveness. In fact, a relative percentage error below 10%, with a coefficient of determination for the prediction higher than 0.9, was obtained, together with a LOD and LOQ of 1.26 and 3.80 mg L−1, respectively, which are much lower than the maximum threshold value established by European Union legislation for histamine in fishery products (200 mg kg−1). These results were obtained with samples containing uncalibrated species and without using toxic reagents, which attest the suitability of the procedure. Globally, the developed methodology proved to be accurate and much simpler and faster than the reference procedures.

Cd-free photoluminescent composites based on the ternary chalcogenides quantum dots

Ternary chalcogenides quantum dots (QDs) are attractive light-converting materials owing to the absence of highly toxic metals (Cd), which are present in currently used QDs. Besides environmental friendliness, they possess broad, composition-tunable emission peaks with long photoluminescence lifetime, in a wide spectral range, which enables their usage as down-converting luminophors for light-emitting devices. Albeit, to improve QDs stability against the environment, as well as to widen an area of their possible applications, solid-state composites with incorporated QDs are preferable. AgInS2 QDs are one of the most prominent members of ternary chalcogenides, which can be synthesized easily. Thus, pristine QDs and QDs with ZnS shell were synthesized and embedded into the CaCO3 matrix. Copper doping can significantly expand the spectral window of AgInS2 QDs to red and NIR regions. Thus we researched Cu alloying with pristine AgInS2 quantum dots by the same means. The impact of the encapsulation on QDs optical properties was investigated using photoluminescence (PL) spectroscopy at ambient and cryogenic temperatures. We observed that QDs-matrix composites show PL in a broad spectral range (550–730 nm). Overall the CaCO3 matrix maintains original PL of incorporated QDs. Insignificant red shifts of PL peaks, especially in the case of Cu-containing QDs are probably caused by the interaction with CaCO3 material. During cryogenic PL measurements (10–300 K) we revealed that generally Cu alloying dramatically suppress AgInS2 QDs thermosensitivity. Copper doping of AgInS2 QDs increases their photostability by trapping of charge carriers at Cu clusters.

Optical Properties of AgInS2 Quantum Dots Synthesized in a 3D-Printed Microfluidic Chip

Colloidal nanoparticles, and quantum dots in particular, are a new class of materials that can significantly improve the functionality of photonics, electronics, sensor devices, etc. The main challenge addressed in the article is modification of the syntheses of colloidal NP to launch them into mass production. It is proposed to use an additive printing method of chips for microfluidic synthesis, and it is shown that our approach allows to offer a cheap, easily scalable and automated synthesis method which allows to increase the product yield up to 60% with improved optical properties of AgInS2 quantum dots.

Improved Luminous Efficiency of AgInS2 Quantum Dots and Zeolitic Imidazolate Framework-70 Composite for White Light Emitting Diode Applications.

The application of multiple quantum dots (QDs) in the field of white light emitting diodes (WLEDs) is still an important challenge due to their low luminous efficiency and quenching phenomenon. In this paper, we prepared AgInS2 QDs/zeolitic imidazolate framework-70 (AIS/ZIF-70) composite by a microwave hydrothermal method. Owing to the high porosity and stability of ZIF-70, it could effectively prevent quenching issues due to the aggregation of QDs. Since the ZIF-70 and QDs were chemically bonded, the formation of the ZnS layer could effectively passivate the surface defect and thus the quantum yield reached 21.49 % in aqueous solution. The luminous efficiency (LE) of the assembled AIS/ZIF-based WLED was reinforced by 6.8 times with a molar ratio of AgIn/Zn=18, i. e. at 5.26 % molar fraction of ZIF-70. Moreover, the color rendering index (CRI) and correlated color temperature (CCT) of AIS/ZIF-based WLED were 84.3 and 3631 K, respectively, indicating its potential application in solid-state lighting.

Detection of enrofloxacin residues in dairy products based on their fluorescence quenching effect on AgInS2 QDs

Water-soluble AgInS2 (AIS) quantum dots (QDs) were successfully prepared through the one-pot water phase method with thioglycolic acid (TGA) as the stabilizing agent. Because enrofloxacin (ENR) effectively quenches the fluorescence of AIS QDs, a highly-sensitive fluorescence detection method is proposed to detect ENR residues in milk. Under optimal detection conditions, there was a good linear relationship between the relative fluorescence quenching amount (ΔF/F0) of AgInS2 with ENR and ENR concentration (C). The detection range was 0.3125–20.00 μg/mL, r = 0.9964, and the detection limit (LOD) was 0.024 μg/mL (n = 11). The average recovery of ENR in milk ranged from 95.43 to 114.28%. The method established in this study has advantages including a high sensitivity, a low detection limit, simple operation and a low cost. The fluorescence quenching mechanism of AIS QDs with ENR was discussed and the dynamic quenching mechanism of light-induced electron transfer was proposed.

Rational Control of Near-Infrared Colloidal Thick-Shell Eco-Friendly Quantum Dots for Solar Energy Conversion.

Thick-shell colloidal quantum dots (QDs) are promising building blocks for solar technologies due to their size/composition/shape-tunable properties. However, most well-performed thick-shell QDs suffer from frequent use of toxic metal elements including Pb and Cd, and inadequate light absorption in the visible and near-infrared (NIR) region due to the wide bandgap of the shell. In this work, eco-friendly AgInSe2 /AgInS2 core/shell QDs, which are optically active in the NIR region and are suitable candidates to fabricate devices for solar energy conversion, are developed. Direct synthesis suffers from simultaneously controlling the reactivity of multiple precursors, instead, a template-assisted cation exchange method is used. By modulating the monolayer growth of template QDs, gradient AgInSeS shell layers are incorporated into AgInSe2 /AgInS2 QDs. The resulting AgInSe2 /AgInSeS/AgInS2 exhibits better charge transfer than AgInSe2 /AgInS2 due to their favorable electronic band alignment, as predicted by first-principle calculations and confirmed by transient fluorescence spectroscopy. The photoelectrochemical cells fabricated with AgInSe2 /AgInSeS/AgInS2 QDs present ≈1.5-fold higher current density and better stability compared to AgInSe2 /AgInS2 . The findings define a promising approach toward multinary QDs and pave the way for engineering the QDs' electronic band structures for solar-energy conversion.

Amino group and F− ions tailored aggregation-based phase transition for manipulating optical properties of AgInS2 quantum dots

Amino group and F− ions tailored aggregation-based phase transition for manipulating optical properties of AgInS2 quantum dots

Zn, Cd and Hg doping of AgInS2 quantum dots – efficient strategy to modify nonlinear absorption

This work aims to investigate a possible strategy to enhance the nonlinear optical absorption in a well-known group of defect-rich ternary AgInS2 quantum dots.

Luminescence technique for studying the growth of AgInS2 quantum dots

Although nanoparticle production techniques are well-known, getting nanoparticles with specific characteristics that enable their application as biosensors is an entirely other problem. Many issues occur as a result of employing the method for producing repeatable and time-stable nanostructures. We created AgInS2 nanoparticles as colloidal quantum dots in a variety of methods to test the efficiency of the synthesis process on the optical characteristics of the nanoparticles, as well as their size, composition, absorption, and luminescence spectra. The capillary electrophoresis (CE) approach for AgInS2 production was employed, with modifications in solvent and temperature, to get nanocrystal (NC) particles. The researchers discovered that Ag accumulation in the InS lattice promotes deformation which leads to structural defects. Consequently, the direction of a nanoparticle light band may now be changed. The features of mixed AgInS2 nanoparticles have been examined with respect to different fabrication procedures, surface stability, and metal impurity incorporation. One band dominates in the luminescence spectra of AgxIn1–xS2 nanoparticles. The relationship between the stoichiometric ratio, luminescence amplitude, line width, and the maximum wavelength is investigated. The average size of the received nanocrystals was determined using dynamic light scattering studies. The computed nanoparticle diameter range has an average particle size of 3–3.5 nm.

High-performance photoelectrochemical immunosensor based on featured photocathode-photoanode operating system

Photocathodic immunosensors generally exhibit fortified anti-interference abilities than photoanodic ones against the detection in biological specimens. Yet, the weak photocurrent signals of the photocathodes have limited evidently the detection performance. Herein, an efficient and feasible photoelectrochemical (PEC) immunosensor was developed on the basis of the featured photocathode-photoanode operating system. In the proposal, the elaborated PEC immunosensor integrated photocathode with photoanode, and the immune recognition occurred just on the photocathode. To illustrate the performance, α-fetoprotein (AFP) was selected as a target antigen (Ag) for detection. TiO2 nanoparticles were decorated with AgInS2 quantum dots (AIS QDs) to fabricate the TiO2/AIS photoanode, and the carbon nanotubes (CNTs) were modified with CuInS2 nanoflowers (CIS NFs) to prepare the CNT/CIS photocathode for the capture AFP antibody (Ab) anchoring. Target Ag detection depended on significant decrease of the photocurrent signal produced by large steric hindrance of the captured AFP molecules. Coupling excellent photoelectric property with anti-interference ability in this elegant PEC immunosensor, sensitive and specific probing of target Ag was realized. The proposed photocathode-photoanode integrating strategy provides a promising way to explore other high-performance PEC immunosensors against the detection in biological matrixes.

Rapid synthesis of AgInS2 quantum dots by microwave assisted-hydrothermal method and its application in white light emitting diodes

Rapid synthesis of AgInS2 quantum dots (AIS QDs) with high quantum yield and crystallinity in aqueous phase has been identified as a research priority in the realm of colloidal semiconductors. Herein, microwave assisted-hydrothermal method was used to react for 5 min at 120 °C to prepare AIS QDs with high luminescence properties. Meanwhile, 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) ionic liquid (IL) was employed as a wave absorber to enhance the photoluminescence quantum yield (PLQY) and shorten the reaction time. The AIS QDs exhibited spectral tunability by adjusting the IL/AgIn molar ratio from 0 to 10, and the luminescence peak position could be tuned from 597 nm to 670 nm. The PLQY of AIS QDs reached 27.67% at the IL/AgIn molar ratio of 2.5, and the fluorescence lifetime upped to 360.4 ns. In addition, the ZnS shell was coated on the surface of the QDs with Zn/AgIn= 3 by reacting at 90 °C for 2 min, and the PLQY could reach to 35.66%, which further improved the emission performance of the AIS QDs. Finally, QDs and commercial (Ba, Sr)Si2O2N2:Eu2+ phosphors were mixed to fabricate white light emitting diodes (WLEDs) devices. AIS@ZnS QDs-based WLED showed color rendering index (CRI) of 87.7 and correlated color temperature (CCT) of 5220 K. And its luminous efficiency (LE) reached 80.13 lm/W, which is 2.16 times higher than that of AIS QDs-based WLED (37.1 lm/W), indicating the good application prospect in WLEDs.

Photoelectrochemical biosensing platform based on in situ generated ultrathin covalent organic framework film and AgInS2 QDs for dual target detection of HIV and CEA

In this work, a new photoelectrochemical (PEC) biosensing platform based on an ordered two-dimensional (2D) ultrathin covalent organic framework (COF) film and AgInS2 quantum dots (QDs) has been developed to enable dual-target detection of HIV and CEA. The porous COF film was firstly in situ generated on ITO, displaying super-stable and intense photocurrent with excellent repeatability. Moreover, an effective PEC quenching probe was specifically designed by loading large number of AgInS2 QDs on Au nanoparticles (NPs). After target HIV-induced cyclic amplification process to generate abundant DNA S0, the Au NPs-AgInS2 QDs probe was binded to the COF film through DNA hybridization, enabling PEC signal of the COF film to turn “off” for ultra-sensitive detection of HIV. Furthermore, when CEA as the second target specifically binded to its aptamer, the Au NPs-AgInS2 QDs quenching probe was released, achieving PEC signal “on” of the T-DA COF film for ultra-sensitive detection of CEA. This work opened a unique 2-D COF film-based PEC biosensing platform with excellent signal for rapid detection of dual targets, which can effectively avoid false positives and negatives and shows promising application for early prevention and detection of cancer diseases.

Aggregation-based phase transition tailored heterophase junctions of AgInS2 for boosting photocatalytic H2 evolution

Due to high defect tolerance and multiphase allowance, AgInS2 (AIS) quantum dots (QDs) provide chances for designing new type junctions via tailoring defects, size, or phase structure. These new type junctions potentially enhance photoelectric performance, such as photocatalytic H2 evolution (PHE). Here, ultra-small AIS QDs (∼1 nm) with well-defined exciton absorption were prepared aqueously via a reverse hot-injection procedure for the first time. A coalescence or fast aggregation-based growth was observed for coarsening at 95 or 135 ℃, respectively. XRD and TEM investigations revealed that the tetragonal-orthorhombic (t-o) phase transition occurred via aggregation-based growth. The studies on phase transition kinetics resulted in fine-tailoring on AIS polymorphs, favoring t-o AIS junctions. UV–vis absorption spectra confirm the double absorption edge of the t-o heterophase junction with enhanced visible absorption. Steady and transient PL spectra suggest improvements in carriers’ separation/transfer in this t-o junction. As a result, the optimized t-o AIS shows superior photocatalytic H2 evolution rates of 1022 μmol. g−1. h−1, 51.1 times that of t-AIS or 3.8 times that of o-AIS. This work is expected to provide new insight for designing ternary alloyed QDs with strongly coupled interfaces for effective H2 generations.

Spectroscopic and structural implications of hosting Zn2+, Cd2+ and Hg2+ ions in the AgInS2 quantum dots

This work address the issue of spectral implications provided by doping AgInS 2 QDs with Zn 2+ and its higher homologues including Cd 2+ and Hg 2+ . The impact of alloying AgInS 2 QD with IIB group atoms is here discussed in terms of comprehensive spectroscopic measurements as well as theoretical predictions performed within the Density Functional Theory. It is shown that each of the admixtures used induces a completely different spectral response including complete reversal character for Cd 2+ and Hg 2+ ions. Observed differences were here associated with changes in the native defects structure and possible relaxation pathways due to doping. It is shown that Zn 2+ ions results in quite weak impact on the emission properties of the AgInS 2 QDs. Highest impact was found for Cd 2+ and Hg 2+ ions. Doping AgInS 2 QDs with Cd 2+ results in successive deactivation of the relaxation pathways which were typical for pristine AgInS 2 QDs leading to significant shortening of the photoluminescence lifetime and partial band symmetrisation. Doping with Hg 2+ ions was found to be of completely opposite character. It was found that mercury adatom has the lowest affinity to the AgInS 2 surface giving rise to formation of metallic Hg-Ag complexes on a surface which may be responsible for anomalous behaviour of Hg-doped AgInS 2 QDs. • Alloying AgInS 2 QDs with Cd and Hg is of different nature to that observed for Zn. • Spectral changes induced by Zn, Cd and Hg alloying are caused by native defects. • Doping with Zn, Cd and Hg ions may either partially passivate or induce defects formation. • Both Cd and Hg ions have much stronger impact on the defects structure than Zn ions. • Mercury dopants form metallic Hg-Ag complexes in AgInS 2 resulting in spectral redshift.

Polyvinylpyrrolidone as a Stabilizer in Synthesis of AgInS2 Quantum Dots.

A synthesis protocol of polyvinylpyrrolidone-capped AgInS2 quantum dots in aqueous solution is reported. Nanoparticle morphology and chemical composition were studied by means of TEM, XRD, XPS, and FTIR. The obtained quantum dots were luminescent in the visible range. The photoluminescence intensity dependence on the polyvinylpyrrolidone amount was demonstrated. The wavelength of the emission maximum varied with changing the [Ag]:[In] molar ratio. The temperature dependence of the photoluminescence intensity of the polyvinylpyrrolidone-capped AgInS2 quantum dots was investigated within the temperature range of 11–294 K.