Au Quantum Dots Research Articles

Preparation and Characterization of Au Quantum Dots Using Laser in Benzene and Study of the Pulse Energy effect on Quantum Size

Here, findings from a study on pulsed laser ablating of noble Au targets submerged in benzene solvent and a study on the effect of pulse energy on quantum size are presented. Three samples of gold quantum dots (AuQDs) are synthesized at pulse fluence of 4, 8, and 12 J/cm2, which is referred to as F1, F2, and F3, respectively. The prepared AuQDs were characterized by UV-Vis, HR-TEM, XRD, XPS, EDX, FTIR, Raman spectroscopy and Photoluminescence measurement. AuQDs that were synthesized have monocrystalline and cubic (FCC) structure, according to XRD patterns. It was found that the direct optical energy gap of AuQDs is enhanced to 2.6 eV. The emission peak of AuQDs photoluminescence emission spectra is at roughly 481, 445, and 437 nm, for F1, F2, F3 samples, respectively. The quantum size was reduced to 2 nm for sample F3. This strategy has the ability to prepare pure AuQDs in one step, with promising biosensor and bioimaging applications.

Fabrication of gradient band tin oxide electron transport layer using self-separated dual-quantum dots for perovskite solar cells

Constructing a gradient band structure electron transport layer (ETL) and thereby enhancing the performance and stability of perovskite solar cells are an effective approach. Leveraging two types of quantum dots (QDs) with different masses, namely GQDs and Au QDs, along with tin oxide (SnO2) colloidal particles, we successfully prepared an ETL with a gradient band structure. Perovskite solar cells fabricated based on this gradient band ETL achieved a power conversion efficiency (PCE) of 22.2%, whereas those prepared with a conventional SnO2 ETL yielded only 19.6% efficiency. Furthermore, under continuous AM 1.5 G and 45°C temperature illumination for 1000 hours, the cells retained 91% of their initial efficiency. Further investigation revealed that the construction of this gradient band structure effectively compensated for the defects of the SnO2, thereby improving its electrical properties. Additionally, it enhanced the transport and separate ability of charge carriers in the ETL, reducing recombination probabilities. This work provides a simple and effective method for constructing gradient band structures, which not only enhances the performance of perovskite solar cells but also holds promise for other photovoltaic conversion devices.

Construction of Au quantum dots/nitrogen-defect-enriched graphite carbon nitride heterostructure via photo-deposition towards enhanced nitric oxide photooxidation

The challenge of mitigating pollution stemming from industrial exhaust emissions is a pressing issue in both academia and industry. This study presents the successful synthesis of nitrogen-defect-enriched graphite carbon nitride (g-C3N4) using a two-step calcination technique. Furthermore, a g-C3N4-Au heterostructure was fabricated through the photo-deposited Au quantum dots (QDs). When subjected to visible light irradiation, this heterostructure exhibited robust nitric oxide (NO) photooxidation activity and stability. With its fluffy, porous structure and large surface area, the nitrogen-defect-enriched g-C3N4 provides more active sites for photooxidation processes. The ability of g-C3N4 to absorb visible light is enhanced by the local surface plasmon resonance (LSPR) effect of Au QDs. Additionally, the lifetime of photogenerated charge carriers is extended by the presence of N defects and Au, which effectively prevent photogenerated electron-hole pairs from recombining during the photooxidation process. Moreover, the oxidation pathway of NO was analyzed through In-situ Fourier transform infrared (FT-IR) spectroscopy and Density Functional Theory (DFT) calculation. Computational findings revealed that the introduction of Au QDs decreases the activation energy of the oxidation reaction, thereby facilitating its occurrence while diminishing the formation of intermediate products. As a result, NO is predominantly converted to nitrate (NO3−). This work unveils a novel approach to constructing semiconductor-cocatalyst heterostructures and elucidates their role in NO photooxidation.

Defect-induced-reduced Au quantum Dots@MXene decorated separator enables lithium-sulfur batteries with high sulfur utilization

Although lithium-sulfur (Li-S) batteries have a high theoretical energy density, their practical applications are limited by rapid capacity fading and poor cycling stability due to the dissolution of high-order polysulfides in electrolytes and the sluggish kinetics of the solid-state Li2S2/Li2S redox reaction. Herein, a polysulfide sorbent and redox reaction catalytic promoter, Au quantum dots (Au QDs)-decorated MXene nanosheet, is designed by proposing defect-induced-reduced Ti3C2Tx (MXene) to improve the performance of Li-S batteries. The polar surface functional groups and high electronic conductivity of the MXene boost the conversion of sulfur/polysulfides and restrict the dissolution of the polysulfide shuttle. The Au QDs catalyst reduces the conversion reaction activation energy to achieve rapid solid-state Li2S2/Li2S reaction kinetics. Due to the adsorption-catalysis synergistic effect between MXene and Au QDs, an initial discharge capacity of 1,500 mA h g-1 is obtained, corresponding to a sulfur utilization of 90%. A Li-S battery based on the Au QDs@MXene-decorated separator exhibits a capacity retention rate of 71.0% for 300 cycles at 1 C.

Guiding the Driving Factors on Plasma Super-Photothermal S-Scheme Core-Shell Nanoreactor to Enhance Photothermal Catalytic H2 Evolution and Selective CO2 Reduction.

Light-induced heat has a non-negligible role in photocatalytic reactions. However, it is still challenging to design highly efficient catalysts that can make use of light and thermal energy synergistically. Herein, the study proposes a plasma super-photothermal S-scheme heterojunction core-shell nanoreactor based on manipulation of the driving factors, which consists of α-Fe2 O3 encapsulated by g-C3 N4 modified with gold quantum dots. α-Fe2 O3 can promote carrier spatial separation while also acting as a thermal core to radiate heat to the shell, while Au quantum dots transfer energetic electrons and heat to g-C3 N4 via surface plasmon resonance. Consequently, the catalytic activity of Au/α-Fe2 O3 @g-C3 N4 is significantly improved by internal and external double hot spots, and it shows an H2 evolution rate of 5762.35µmol h-1 g-1 , and the selectivity of CO2 conversion to CH4 is 91.2%. This work provides an effective strategy to design new plasma photothermal catalysts for the solar-to-fuel transition.

An enzyme free self-cascade catalytic system with Au deposited bimetallic organic framework as a dual active nanozyme for glucose detection with a smartphone readout platform

A new kind of dual active biomimetic nanozyme was constructed for the establishment of an enzyme free self-cascade catalytic system. Herein, Au/FeNi-MOF nanozyme was designed and constructed by depositing Au quantum dots on a three-dimensional bimetallic organic framework via electrostatic self-assembly. By regulating the immobilization of Au quantum dots on the surface of FeNi-MOF, Au quantum dots not only exhibited stable glucose oxidase-like activity (GOx-like), but enhanced the peroxidase-like activity (POD-like) of FeNi-MOF. The obtained Au/FeNi-MOF nanozyme with both GOx-like and enhanced POD-like activities was used to mimick the cascade catalytic reaction of natural enzymes, thereby construct an enzyme free self-cascade catalytic colorimetric detection system for glucose. The detection method has a linear range of 0.02–10 mM and a detection limit as low as 15 μM with good accuracy and reproducibility. Based on the above performance, a smartphone readout platform for glucose detection was further developed. In this scheme the smartphone was used to extract and recognize the RGB values of the reaction system which were consequently converted into gray values. We recognized that evaluating glucose levels through a smartphone readout platform has the advantage of simple, convenient, and reliable, while revealing its potential application in medical monitoring.

Tuning the SERS Capabilities of ZnO Nanowire Arrays Functionalized with Au Quantum Dots for Highly Sensitive Detection of Methylene Blue

AbstractThe development of a surface enhanced Raman scattering (SERS) substrate capable of sensing the target analyte at low concentration has always been demanding. In this prospective, ZnO−Au quantum dots (QDs) hybrid structure with tunable surface properties and high chemical stability is considered a promising material for SERS applications. Here, a novel ZnO@Au QDs hybrid structures with various amounts of Au QDs (ZnO−Aux QDs, where x=0.2, 0.4, 0.6 and 1.0) was synthesized by employing solvothermal along with electrodeposition approach. The optimized substrate, ZnO@Au QDs (0.6) exhibits excellent SERS sensitivity for the detection of MB up to 1 nM with a good reproducibility. The chemical and compositional analysis show that the surface defects are formed due to the interface interactions which not only promote charge transfer between ZnO nanowires and Au QDs complex but also enhanced the Raman scattering of target analyte. The developed substrate demonstrates excellent SERS uniformity which makes them reliable choice for the detection of multi‐analyte for practical applications.

Regulation on the electrical and optical properties of two-dimensional stacked graphene quantum dots/gold quantum dots/tungsten sulfide heterostructures

Two-dimensional (2D) transition metal dichalcogenides (TMDCs), like WS2, have been particularly promising in the application of solar energy conversion. Nevertheless, how to enhance the absorption capacity and photogenerated dcharge transfer is yet challenging. Herein, 2D stacked heterostructures were firstly constructed by 2D Au quantum dots (QDs), graphene quantum dots (GQDs) and WS2 monolayer. Compared with WS2 monolayer, the absorption abilities of the Au QDs/WS2 heterostructures in visible-near infrared light region of 450–2300 nm increase evidently. Simultaneously, charge redistribution occurs at the WS2–Au interfaces and generates the built-in electric field with the direction from Au QDs to the WS2 monolayer. This built-in electric field is conducive to boosting photo-induced charge separation and transfer. Notably, more obvious charge transfer and stronger built-in electric field can be achieved in WS2–Au6 interface after introducing the GQDs. Therefore, this work provides unique insights for designing new WS2-based heterostructures to improve the solar energy conversion.

Controllable Ga/Ga2O3 Nanowire Growth at High Temperatures Enabled by Au and Pd Quantum Dot Catalysts

Controllable Ga/Ga₂O₃ Nanowire Growth at High Temperatures Enabled by Au and Pd Quantum Dot Catalysts

Construction of Au and C60 quantum dots modified materials of Institute Lavoisier-125(Ti) architectures for antibiotic degradation: Performance, toxicity assessment, and mechanistic insight

High-performance and stabilized photocatalytic degradation of antibiotic contaminants still remains a challenge in environmental photocatalysis and has been studied worldwide. In this work, hybrid Au and C60 quantum dots decorated Materials of Institute Lavoisier-125(Ti) (MIL-125(Ti)) composites were successfully fabricated for visible-light photocatalytic tetracycline degradation with pristine MIL-125(Ti) as a comparison. The experimental results revealed that the introduction of C60 quantum dots and Au nanoparticles resulted in highly enhanced visible-light harvesting and charge separation for efficient tetracycline degradation. The optimal Au/C60-MIL-125(Ti)-1.0% sample exhibited the highest visible-light photocatalytic performance, and the corresponding rate constant was approximately 9.19 times of MIL-125(Ti), indicating the significant roles of Au and C60 quantum dots in boosting visible-light absorption and charge separation. Furthermore, the radical species, possible degradation pathways and toxicity assessment, and photocatalytic mechanism were also investigated. Current work indicates a synergistic strategy for enhancing visible-light harvesting and charge separation to fabricate high-performance composite photocatalysts.

Au-quantum dot nanocluster electrochemiluminescence coupled with cycling-amplification for sensitive microRNA detection

A novel polyamidoamine (PAMAM) dendrimer-Au nanocluster composite was synthesized, and used to fabricate a new amplified electrochemiluminescence (ECL) signal probe for sensitive detection of microRNA by multiple strand displacement amplification (SDA) strategy. The as prepared PAMAM-Au nanocluster with many amino groups could assemble a large number of quantum dots (QDs) to greatly amplify ECL of the probe. In addition, a new sliver nanocluster (NC) with excellent conductivity and many reactive carboxyl groups was prepared, and used to immobilize a large amount of capture (c1) DNA molecules on the electrode. Moreover, by using bifunctional DNA strand displacement reaction-mediated multiple cycling-amplification technique, a small number of target miRNA could induce to generate abundant DNA (t1) fragments, which was used as a linker to hybridize with c1 DNA on the electrode, and then conjugate many amplified QDs probe. Thus an amplified ECL analytical method for detecting target miRNA was designed, and highly sensitive detection of miRNA was achieved. This newly established strategy paves a new way for homogeneous microRNA detection, which hold great potential for application in early clinical diagnosis.

Memory effect of vertically stacked hBN/QDs/hBN structures based on quantum-dot monolayers sandwiched between hexagonal boron nitride layer

The characteristics of a flexible write-once-read-many-times (WORM) memory fabricated with monolayered 0-dimensional (0D) CdSe–ZnS quantum dots (QDs) layers sandwiched between two insulating 2-dimensional (2D) hexagonal boron nitride (hBN) multilayers were investigated by electrical measurement method. The hBN/QDs monolayer/hBN structure was fabricated in a vertical stacked structure using a technique which control the formation of the QDs monolayer. QDs monolayer was formed by electrostatic interaction between the negative charge group on the CdSe–ZnS QDs surface and the positive charge group on the hBN surface. The device has a WORM characteristic due to the presence of QDs in the current-voltage (I–V) measurement. When a bias is applied, carriers were initially trapped by tunneling due to the QDs and then a conductive filament was formed in the hBN, which were not detrapped and exhibit characteristics of write-once-read-many-times memory. The maximum ON/OFF ratio of the current for the devices was as large as 4 × 10, and the endurance was 5 × 10 4 cycles, and a retention time was larger than 1 × 10 5 s. In order to explain the carrier transport mechanism and conductive filament of the WORM memory device caused by QDs, it through various methods such as I–V fitting data, simulation, and conductive AFM. Unlike the conventional conductive filament mechanism, through random diffusion such as Ag filament, the Au/hBN/QD/hBN/ITO/PET structures implemented a consistent conductive filament using Au metal and QDs active layer.

Nanocomposite of Au and black phosphorus quantum dots as versatile probes for amphibious SERS spectroscopy, 3D photoacoustic imaging and cancer therapy

To expand the bioimaging applications of Au and black phosphorus, black phosphorus quantum dot-Au hybrids (Au-BPQD nanohybrids) are fabricated for multiple theranostic applications in this study. By simply varying the ratios of BPQDs and Au3+, the BPQDs assisted Au3+ reduction outputs two kinds of nanohybrids with different functions. The less BPQDs lead to small size Au-BPQD nanohybrids (S-ABPs) with a core-shell structure. S-ABPs exhibit superior near-infrared (NIR) surface-enhanced Raman scattering (SERS) activity for the fingerprint analysis of biomolecules. It's also very promising for interference-free bioimaging due to the distinctive Raman band at around 2190 cm−1 in the biologically Raman-silent region, which cannot be achieved by Au or BP-based nanomaterials. Meanwhile, further addition of BPQDs would lead to large size Au-BPQD nanohybrids (L-ABPs) with strong NIR optical absorption, which facilitates the in vivo 3D photoacoustic imaging as well as the photothermal therapy against tumor. This work reports versatile nanotheranostic platforms for amphibious SERS spectroscopy, 3D photoacoustic imaging and cancer therapy, which opens a new door for the biomedical applications of BP and Au based nanomaterials.

Discussions of Fluorescence in Selenium Chemistry: Recently Reported Probes, Particles, and a Clearer Biological Knowledge.

In this review from literature appearing over about the past 5 years, we focus on selected selenide reports and related chemistry; we aimed for a digestible, relevant, review intended to be usefully interconnected within the realm of fluorescence and selenium chemistry. Tellurium is mentioned where relevant. Topics include selenium in physics and surfaces, nanoscience, sensing and fluorescence, quantum dots and nanoparticles, Au and oxide nanoparticles quantum dot based, coatings and catalyst poisons, thin film, and aspects of solar energy conversion. Chemosensing is covered, whether small molecule or nanoparticle based, relating to metal ion analytes, H2S, as well as analyte sulfane (biothiols—including glutathione). We cover recent reports of probing and fluorescence when they deal with redox biology aspects. Selenium in therapeutics, medicinal chemistry and skeleton cores is covered. Selenium serves as a constituent for some small molecule sensors and probes. Typically, the selenium is part of the reactive, or active site of the probe; in other cases, it is featured as the analyte, either as a reduced or oxidized form of selenium. Free radicals and ROS are also mentioned; aggregation strategies are treated in some places. Also, the relationship between reduced selenium and oxidized selenium is developed.

Colloidal Assembly of Au-Quantum Dot-Au Sandwiched Nanostructures with Strong Plasmon-Exciton Coupling.

Strong plasmon-exciton coupling could occur in hybrid metal-dye/semiconductor nanostructures, where the fast energy exchange between plasmons and excitons leads to two new eigenmodes of the system, known as Rabi splitting. In experiments, strongly coupled nanosystems are difficult to obtain because they require some strict conditions, such as low plasmonic damping, small plasmon mode volume, and good spectral overlap. This work demonstrates strongly coupled metal-semiconductor nanostructures can be constructed using colloidal assembly. Specifically, sandwiched Au-quantum dot-Au nanostructures were created through the assembly of Au nanoparticles and colloidal quantum dots (QDs). The sizes of the QDs and the assembly conditions were varied to control the mode volume of the plasmonic cavity formed between the two Au nanoparticles. With a decreased gap size, Rabi splitting was observed in both dark-field scattering and fluorescence spectra of single Au-QD-Au nanostructures. Theoretical simulations revealed that the strong coupling occurred between the excitons and the octupolar plasmon modes.

Selective and sensitive visible-light-prompt photoelectrochemical sensor of Cu2+ based on CdS nanorods modified with Au and graphene quantum dots

Nowadays, increasing the risk for copper leaching into the drinking water in homes, hotels and schools has become unresolved issues all around the countries such as Canada, the United States, and Malaysia. The leaching of copper in tap water is due to a combination of acidic water, damaged pipes, and corroded plumbing fixtures. To remedy this global problem, a triple interconnected structure of CdS/Au/GQDs was designed as a photo-to-electron conversion medium for a real time and selective visible-light-prompt photoelectrochemical (PEC) sensor for Cu2+ ions in real water samples. The synergistic interaction of the CdS/Au/GQDs enabled the smooth transportation of charge carriers to the charge collector and provided a channel to inhibit the charge recombination reaction. Thus, a detection limit of 2.27 nM was obtained, which is 10,000 fold lower than that of WHO’s Guidelines for Drinking-water Quality (∼30 μM). The photocurrent reduction was negligible after 30 days of storage under ambient conditions, suggesting the high stability of photoelectrode. Moreover, the real-time monitoring of Cu2+ ions in real samples was performed with satisfactory results, confirming the capability of the investigated photoelectrode as the most practical detector for trace amounts of Cu2+ ions.

Multifunctional Heterogeneous Carbon Nanotube Nanocomposites Assembled by DNA-Binding Peptide Anchors.

Although carbon nanotubes (CNTs) are remarkable materials with many exceptional characteristics, their poor chemical functionality limits their potential applications. Herein, a strategy is proposed for functionalizing CNTs, which can be achieved with any functional group (FG) without degrading their intrinsic structure by using a deoxyribonucleic acid (DNA)-binding peptide (DBP) anchor. By employing a DBP tagged with a certain FG, such as thiol, biotin, and carboxyl acid, it is possible to introduce any FG with a controlled density on DNA-wrapped CNTs. Additionally, different types of FGs can be introduced on CNTs simultaneously, using DBPs tagged with different FGs. This method can be used to prepare CNT nanocomposites containing different types of nanoparticles (NPs), such as Au NPs, magnetic NPs, and quantum dots. The CNT nanocomposites decorated with these NPs can be used as reusable catalase-like nanocomposites with exceptional catalytic activities, owing to the synergistic effects of all the components. Additionally, the unique DBP-DNA interaction allows the on-demand detachment of the NPs attached to the CNT surface; further, it facilitates a CNT chirality-specific NP attachment and separation using the sequence-specific programmable characteristics of oligonucleotides. The proposed method provides a novel chemistry platform for constructing new functional CNTs suitable for diverse applications.

Dual quantum dots decorated TiO2 nanorod arrays for efficient CO2 reduction

To meet the demand of CO2 reduction, we designed a Z-type composite photocatalyst based on vertically aligned rutile TiO2 (r-TiO2) nanorod arrays. The composite photocatalyst was obtained by decorating g-C3N4 and Au quantum dots on the r-TiO2 nanorods. Benefiting from the high charge separation efficiency of C3N4/TiO2 heterojunction and the electron capture effect of Au quantum dots, the composite catalyst indicates a significantly enhanced hydrocarbon yield efficiency. The yield rate of CO can increase to 0.138 μmol cm−2 h−1 and the yield rate of CH4 can reach 0.032 μmol cm−2 h−1 without any sacrificial agents, which is almost 5 times than that of pristine r-TiO2 nanorod arrays. This work provides an efficient strategy to rationally design high-performance photocatalysts by using quantum dots and nanorods (or nanowires) as building blocks.

Nano‐sensor Based on MoS2 Nanosheet mixed with Au quantum dot: Role of Layer Number and Temperature

AbstractThe performance of nano‐sensor based on MoS2 nanosheet mixed with Au particle is tested based electrochemical test involving cyclic voltammogram and impedance spectroscopy, where the FeIII(CN)63−/FeII(CN)64− and dopamine (DA) are chosen as research object to verify the role of layer number of MoS2 nanosheet and the temperature. The electrochemical test shows the Au nanoparticle would improve the electron exchange reaction occurring on the electrode. In the solution of FeIII(CN)63−/FeII(CN)64−, the electrode reaction follows , where increasing the layer number of MoS2 nanosheet would restrict the reaction. In the DA system, the reaction of occurs on the electrode and increasing the layer number of MoS2 nanosheet would facilitate the reaction. The difference as mentioned above is assigned to the energy level shift originated from variance of layer number of MoS2 nanosheet and the changing of reaction mechanism. In addition, temperature would mainly facilitate the kinetics of electron exchange reaction, which is assigned to the diffusion acceleration of DA molecule. Simultaneously, the desorption process of reactant in the electrolyte would enhance. The role of layer number of MoS2 nanosheet and the temperature is clarified with the thermodynamic and kinetic properties of electron exchange reaction based on MoS2 nanosheet, which would improve the understanding of nano‐sensor based on MoS2 nanosheet.

Modeling Plasmon-Induced Hot-Carrier Transfer

In this issue of Chem , Zhang et al. use first-principle simulations (i.e., no empirically adjustable parameters) to elucidate the detailed mechanisms of plasmon-induced hot-carrier transfer at a heterojunction interface between a plasmonic gold nanomaterial and a semiconductor. Together with earlier work by Long and Prezhdo, this study shows how the donor-acceptor interaction at the interface determines the mechanism by which plasmonic excitations lead to hot-electron transfer at interfaces.