Ag Quantum Research Articles

Ag quantum dots-doped poly (vinyl alcohol)/chitosan hydrogel coatings to prevent catheter-associated urinary tract infections

The prevention of catheter-associated urinary tract infections (CAUTIs) significantly impacts the reduction of morbidity and mortality associated with the use of indwelling urinary catheters. This study focused on developing an antibacterial double network hydrogel coating for latex urinary catheters, which incorporated Ag quantum dots (Ag QDs) in a polyvinyl alcohol (PVA)-chitosan (CS) double network hydrogel matrix. The PVA-CS-Ag QDs, referred to as the PCA hydrogel coating exhibited excellent mechanical and physiochemical properties with controlled release of Ag QDs. The antibacterial properties of the PCA hydrogel-coated urinary catheters were studied against both gram-negative Escherichia coli (E. coli, ATCC25922) and gram-positive Staphylococcus aureus (S. aureus, ATCC29213). The continuous release of CS oligomers and Ag QDs from the hydrogel coating contributed to the synergistic antibacterial and antiadhesion effects. Measurements of the Ag release rate revealed that even after 30 days, the concentration of Ag QDs from the PCA hydrogel-coated urinary catheters remained significantly higher than the effective antibacterial concentration of the total Ag (0.1 μg·L−1). These results indicated that the PCA hydrogel coating not only efficiently prevented bacteria attachment, but also exhibited long-term antibacterial activity, thereby inhibiting biofilm formation. Furthermore, the PCA hydrogel-coated urinary catheter demonstrated excellent biocompatibility and hemocompatibility. Overall, this novel PCA hydrogel-coated urinary catheter, with its exceptional antibacterial properties, holds great potential in reducing the incidence of CAUTIs.

Construction of 0-dimensional silver quantum dot/MoSe2@MXene/3-dimensional porous copper foam composite electrodes with heterogeneous interfaces for synergistic electrocatalytic degradation of antibiotics

This study proposes a novel and efficient Ag quantum dots (QDs)/MoSe2@two-dimensional transition metal carbide/nitride (MXene)/copper foam (CF) composite electrode to address the challenge of electrocatalytic degradation of antibiotics in water. The electrode formed a unique electron donor–acceptor system by loading Ag QDs and heterostructured nanosheets on CF, significantly facilitating charge transfer and segregation at the interface. The catalytically active sites at the edges and defective locations of MoSe2 in conjunction with the two-dimensional MXene structure, which formed an efficient electron transfer channel, promoted the electron transfer from the interior to the surface and accelerated the hydrogen adsorption and reduction reactions. Moreover, the charge redistribution at the interface of Ag QDs and MoSe2@MXene formed interfacial dipoles, increasing the active sites on the catalyst surface and promoting the generation of cathodic atomic hydrogen (H*). Under optimal conditions, the degradation rate of tigecycline (TGC) reached as high as 90.1 % ± 2.4 % within 60 min. The anode-generated OH and HClO, along with the cathode-generated H, further promoted the degradation of TGC through co-catalysis. The degradation pathways were analyzed using density-functional theory (DFT) calculations and liquid chromatography-mass spectrometry (LC-MS) techniques. Moreover, toxicity analysis of the degradation products was carried out to ensure the safety of the treated wastewater discharge. A reflux continuous effluent reactor was also designed to achieve high degradation efficiency and low energy consumption after stable operation, laying the foundation for industrial applications. This technology provides new ideas for the design of green, efficient, stable, and low-consumption electrocatalytic reactors and contributes to a sustainable future environment.

Ag QDs modified BiOCl/UiO-66-NH2 Z-scheme heterojunction for accelerated visible light-driven photocatalytic degradation of ciprofloxacin

Ag quantum dots (QDs) anchored on the surface of BiOCl/UiO-66-NH2 Z-scheme heterojunctions were synthesized and characterized by various techniques such as X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (UV–vis DRS), electrochemical impedance spectroscopy (EIS), and photoluminescence (PL). The effects of Ag QDs loading, pH values and co-existing anions on the photocatalytic performance were comprehensively analyzed. The results concluded that the Ag QDs modified catalysts exhibited excellent photocatalytic performance for the degradation of ciprofloxacin (CIP), especially, the catalyst with 5 % Ag QDs loading (referred to as ABU-5) achieved a degradation efficiency of 72 % within 120 min and the apparent reaction rate constant was 0.00538 min−1. The outstanding performance of the ABU-5 catalyst is attributed to the introduction of Ag QDs as electron transfer bridges, improving visible light absorption and enhancing charge transfer between BiOCl and UiO-66-NH2. Free radical trapping experiments and leaching tests were carried out to determine the contribution rates of reactive species to the degradation efficiency and the concentration of Ag+ in solution after the reaction. The possible degradation pathways of CIP by ABU-5 were investigated by gas chromatography-mass spectrometry (GC-MS).

Oxygen-deficient NH4V4O10 cathode with Ag quantum dots and interlayer Ag+ towards high-performance aqueous zinc ion batteries

Herein, oxygen-deficient NH4V4O10 micro-flowers with loaded Ag quantum dots and pre-intercalated Ag+ (NVO-Ag) for aqueous zinc ion battery (AZIB) cathode materials were successfully synthesized by a one-step hydrothermal method. The reversible redox reaction between Ag+ and Ag quantum dots, and the abundant Zn2+ storage sites from oxygen vacancies provided capacity contributions for NVO-Ag. Meanwhile, the loaded Ag quantum dots, pre-intercalated Ag+ and introduced oxygen vacancies synergistically optimized the electronic structure and distribution of NVO-Ag, promoting the transport of electrons in NVO-Ag. The pre-intercalated Ag+ could also replace the NH4+ in the interlayer of NH4V4O10, weakening the repulsion between the interlayer NH4+ and Zn2+, which achieved rapid Zn2+ diffusion kinetics. Moreover, the abundant oxygen vacancies in NVO-Ag could alleviate the strong electrostatic interaction between Zn2+ and V-O framework, boosting the transmission of Zn2+ in NVO-Ag. Finally, the structural stability of NH4V4O10 micro-flowers was improved due to the high bonding strength between Ag+ and V-O layers. Benefiting from the above effects, NVO-Ag-100 achieved excellent capacity performance (387.2 mAh g−1 at 0.5 A g−1), rate performance (178.9 mAh g−1 at 12 A g−1) and cycle stability (91.7 % capacity retention after 1700 cycles at 8 A g−1). This work provided effective ideas to achieve high-performance AZIB cathode materials.

Ultrasound-responsive ZnS:Ag QDs loaded TiO2 biointerfaces: In situ sonodynamic antimicrobial therapy for biomedical implants

Sonodynamic therapy (SDT) is extensively utilized for its profound tissue penetration capabilities in treating deep-seated infections, yet achieving precise ultrasonic treatment at the implant surface remains challenging. Herein, details the development of a novel infection microenvironment-sensitive nano-interface (TN-HHTZ), aimed at enhancing SDT efficacy for treating implant-related infections. The ZnS:Ag quantum dots (ZnS:Ag QDs) are functionalized using tyramine-modified hyaluronic acid (HA-Tyr) and horseradish peroxidase (HRP), resulting in the formation of a hydrogen peroxide (H2O2)-sensitive composite sonosensitizer (HHTZ). HHTZ is loaded onto a titanium dioxide nanotube (TN) array to form TN-HHTZ. Upon infection, ultrasonic triggering causes the rapid release of HHTZ, which interacts with H2O2 in the infected area to form a gel, thereby enabling prolonged enrichment of ZnS:Ag QDs at the site of implant infection. The doping of Ag in ZnS:Ag QDs enhances energy conversion, enabling TN-HHTZ to generate a significant amount of reactive oxygen species (ROS) during the SDT process, thereby boosting its antimicrobial efficacy and ensuring sustained antimicrobial activity throughout the infection period. The TN-HHTZ hydrogel on the implant surface promotes bone cell proliferation and recovery, providing an innovative and holistic strategy for treating and recovering from implant-associated microbial infections.

Highly dispersed Ag quantum dots anchored on palmitic acid/ graphitic carbon nitride composite phase change materials for enhanced photo-thermal storage

Phase change materials (PCM) have attracted much attention in the field of thermal energy storage because of exceptional heat storage capacity, stable operating temperature, and recyclability. However, organic phase change materials, represented by palmitic acid (PA), are limited by inherent leakage problem, unsatisfactory thermal responsiveness and inefficient photo-thermal storage capacity, which severely hamper the development of PCMs technology. As a means of addressing these challenges, we developed one novel support material with 2D/0D structure for palmitic acid via thermal polymerization, specifically, in which highly dispersed Ag quantum dots (Ag QDs) was firmly anchored on graphitic carbon nitride (g-C3N4). PA was further infiltrated into the layered structure of nanoporous g-C3N4/Ag QDs to successfully synthesize novel shape-stabilized PA/g-C3N4/Ag QDs composite phase change materials (CPCM). On the one hand, benefiting from the tightly stacked porous structure of g-C3N4/Ag QDs, PA is effectively encapsulated to avoid leakage problem during the solid-liquid transition with a superior adsorption capacity up to 65 %. On the other hand, the combination of g-C3N4 and Ag QDs in PA/g-C3N4/Ag QDs CPCM demonstrated a synergistic effect resulting in faster heat transfer capability and more efficient solar energy capture capability compared to pure PA, which is capable of dual utilization of heat and solar energy. The newly developed PA/g-C3N4/Ag QDs CPCM features a high melting latent heat and an appropriate phase change temperature, which are 128.35 J/g and 61.92 °C, respectively. The corresponding solidification enthalpy and temperature are 121.70 J/g and 60.02 °C. The photo-thermal conversion efficiency of the material is improved to 78.6 %, facilitating a rapid capture and storage of solar energy. Furthermore, through the optimization of the preparation process, Ag QDs are densely anchored on the surface of g-C3N4, which retains the excellent properties of metallic silver while eliminates the metal agglomeration phenomenon after repeated utilization of CPCMs. PA/g-C3N4/Ag QDs CPCM is proved to be extremely recyclable and thermally stable after massive thermal cycles. This innovative and operational encapsulation modified method significantly optimizes the practicality of phase change materials. The obtained shape-stabilized PA/g-C3N4/Ag QDs CPCM is more versatile, and its unique comprehensive properties can provide high-quality materials for photo-thermal storage systems.

Folic acid capping Bi3+-doped Ag quantum dots for enzyme-like dual-mode recognition of toxic S2− and visual sensing of NO2−

BackgroundNO2− and S2− are two kinds of common toxic anions widely distributed in environmental water, soil and food products. Human beings have suffered a lot of diseases from intake of excessive NO2− or S2−, i.e., infantile methemoglobin, cancer and even to death. Although tremendous efforts have been afforded to monitor NO2− and S2−, most were high instrument-depended with complex processing procedures. To keep food safety and to protect human health, it will be a huge challenge to develop a convenient and efficient way to monitor S2− and NO2− in practice. ResultsA kind of folic acid capping Bi3+-doped Ag quantum dots (FA@Bi3+-Ag QDs) was developed for the first time by one-pot homogeneous reduced self-assembly. Not only did FA@Bi3+-Ag QDs possess intrinsic fluorescent property, it expressed synergistic peroxidase-like activity to catalyze the redox of 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2 with Km/vmax of 0.087 mM/6.61 × 10−8 M s−1 and 6.42 mM/6.25 × 10−7 M s−1 respectively. Interestingly, trace S2− could exclusively alter its fluorescent property and peroxidase-like activity, exhibiting significant hypochromic and “turn-on” fluorescent effects. While trace NO2− could make FA@Bi3+-Ag QDs-TMB-H2O2 system hyperchromic. Under the optimized conditions, FA@Bi3+-Ag QDs were applied for dual-mode recognition of S2− and visual sensing of NO2− in real food samples with satisfactory recoveries, i.e., 100.7–107.9 %/95.8–104.7 % and 97.2–104.8 % respectively. The synergistic enzyme-mimic mechanism of FA@Bi3+-Ag QDs and its selective response mechanisms to S2− and NO2− were also proposed. SignificanceThis represents the first nanozyme-based FA@Bi3+-Ag QDs system for dual-mode recognition of S2− and visual sensing of NO2−, well meeting the basic requirement in drinking water set by WHO. It will offer a promising way for multi-mode monitoring of different pollution using the same nanozyme-based sensor.

Localized surface plasmon-enhanced nanorod micro-LEDs with Ag nanoparticles embedded in insulating and planarizing spin-on glass

To enhance the emission of GaN-based Micro-LEDs (μLEDs), we etched uniform nanorods (NRs) on the μLED surface and filled the nanorod gaps with spin-on glass (SOG) containing mixed Ag nanoparticles (NPs). The nanorod structure creates a conducive environment for close interaction between Ag NPs and quantum wells (QWs), facilitating the coupling of Ag NPs as localized surface plasmons (LSPs) with the QWs to enhance light emission. The SOG acts as an insulating layer between Ag NPs and NRs, preventing electron leakage, while also serving as a planarization material for the nanorod structure. This configuration allows for the fabrication of a planar Indium Tin Oxide layer without short-circuiting the nanorod structure. Compared to traditional planar Micro-LEDs, NR-μLEDs with SOG-encased Ag NPs exhibit a 50% increase in electroluminescence (EL) intensity and a 56% increase in photoluminescence (PL) intensity. This work paves the way for broader applications of LSP in μLEDs.

Fluorescence Enhancement of CdS:Ag Quantum Dots Co-Assembled with Au Nanoparticles in a Hollow Nanosphere Form.

Colloidal quantum dots (QDs) have exceptional fluorescence properties. Overcoming aggregation-induced quenching and enhancing the fluorescence of colloidal QDs have remained a challenging issue in this field. In this study, composite hollow nanospheres composed of Au nanoparticles (NPs) and CdS:Ag-doped QDs were successfully constructed through controlled microemulsion-based cooperative assembly. This method harnessed the localized surface plasmon resonance (LSPR) effect of Au NPs nearby doped QDs, resulting in enhanced doped QD fluorescence and the observation of the Purcell effect. The composite hollow nanospheres show a fluorescence enhancement compared to that of the pure CdS:Ag QDs. The enhanced fluorescence was demonstrated to come from the synergetic enhancement of the absorption and emission transition of the doped QDs. This approach provides a feasible technological pathway to address the challenge of improving the fluorescence performance of the doped QDs.

High Color Conversion Efficiency Realized in Graphene‐Connected Nanorod Micro‐LEDs Using Hybrid Ag Nanoparticles and Quantum Dots

AbstractIn this paper, a uniform nanorod (NR) array is etched onto the surface of Micro‐Light‐Emitting‐Diodes (µLEDs) and mix Ag nanoparticles (NPs) with QDs to fill the gaps between the nanorods. Simultaneously, the study utilizes graphene to connect individual nanorods and enhance current spreading. The nanorod array's structure significantly reduces the distance between the QDs and the quantum well (QW), reducing energy loss from the excitation light source through a non‐radiative energy transfer (NRET) mechanism. Additionally, the Ag NPs function as localized surface plasmons (LSPs), further enhancing the CCE of QDs via the absorption resonance. In this study, the effects of two types of Ag NPs are compared with different absorption resonance peaks on device performance. The results demonstrate that Ag NPs with absorption resonance peaks matching the emission wavelength of QDs play a more crucial role in the system. This configuration achieves a CCE of 77.78% for µLEDs with nanorod arrays, operating at a current of 10 mA. Compared to the conventional µLED structure with QDs only on the surface, the proposed method improves the CCE of µLEDs by an impressive 86.5%. This outcome underscores the significant contribution of the NR structure and LSPs in enhancing the CCE of QD‐µLEDs.

Exploring superparamagnetic and intercalated Ag quantum particles in manganese oxide/graphene oxide for rapid and scalable organic pollutant removal

Exploring superparamagnetic and intercalated Ag quantum particles in manganese oxide/graphene oxide for rapid and scalable organic pollutant removal

3D porous ZnO microspheres sensitized by Ag quantum dots for highly responsive TEA sensors

The study aims to create a highly responsive gas sensor for TEA. In order to achieve this goal, spherical ZnO with layered structure was synthesized by a simple hydrothermal method. Subsequently, Ag quantum dots (QDs) are precipitated onto the surface of the ZnO microspheres. The ZnO microspheres were analyzed to demonstrate that they are comprised of porous nanosheets measuring roughly 10 μm in diameter. The composite with the optimal mass percentage displayed outstanding sensitivity to triethylamine (TEA), yielding a response of 1223, approximately 90 times higher than that of the pure ZnO sensor. Furthermore, this composite also demonstrated remarkable selectivity towards TEA. The exceptional detection results were achieved due to the catalytic influence of Ag as a precious metal, coupled with the distinctive structure of quantum dots and ZnO materials.

Simultaneous photocatalytic degradation and SERS detection of tetracycline with self-sustainable and recyclable ternary PI/TiO2/Ag flexible microfibers

Facile and efficient photocatalysts using sunlight, as well as fast and sensitive surface-enhanced Raman spectroscopy (SERS) substrates, are urgently needed for practical degradation of tetracycline (TC). To meet these requirements, a new paradigm for PI/TiO2/Ag organic‒inorganic ternary flexible microfibers based on semiconducting titanium dioxide (TiO2), the noble metal silver (Ag) and the conjugated polymer polyimide (PI) was developed by engineering a simple method. Under sunlight, the photocatalytic characteristics of the PI/TiO2/Ag flexible microfibers containing varying amounts of Ag quantum dots (QDs) were evaluated with photocatalytic degradation of TC in aqueous solution. The results demonstrated that the amount of Ag affected the photocatalytic activity. Among the tested samples, PI/TiO2/Ag-0.07 (93.1%) exhibited a higher photocatalytic degradation rate than PI/TiO2 (25.7%), PI/TiO2/Ag-0.05 (77.7%), and PI/TiO2/Ag-0.09 (63.3%). This observation and evaluation conducted in the present work strongly indicated a charge transfer mechanism. Moreover, the PI/TiO2/Ag-0.07 flexible microfibers exhibited highly sensitive SERS detection, as demonstrated by the observation of the Raman peaks for TC even at an extremely low concentration of 10–10 moles per liter. The excellent photocatalytic performance and SERS detection capability of the PI/TiO2/Ag flexible microfibers arose from the Schottky barrier formed between Ag and TiO2 and also from the outstanding plasmonic resonance and visible light absorptivity of Ag, along with immobilization by the PI. The successful synthesis of PI/TiO2/Ag flexible microfibers holds significant promise for sensitive detection and efficient photocatalytic degradation of antibiotics.

Low-temperature and high-selectivity Ag/Co3O4 toluene sensor based on lattice oxygen and d-band and investigation of response behavior shifts induced by Ag nanoparticles

Currently, the sensing mechanism of toluene remains controversial. The sensing action of toluene is often attributed to adsorbed oxygen based on acknowledged Wolkenstein model. However, the role of lattice oxygen often remains neglected. To investigate toluene sensing mechanism, Ag quantum dot-modified Co3O4 were successfully synthesized by the thermal method. X-ray photoelectron spectroscopy (XPS) of Ag-Co3O4 before and after exposure to toluene reveal the role of lattice oxygen, and Gas Chromatography-Mass Spectrometry (GC-MS) and Density Functional Theory (DFT) reveal the catalytic role of Ag particles. Ag particles caused the upshift of Co D-band, more readily hybridizing the s and p orbitals in the toluene and O2 molecules, possibly contributing to the enhanced catalytic and adsorption activity of the materials. Moreover, Ag-induced response behaviors switching from oxidation-reduction transitions were found and explained. Excitingly, the synthesized 16 at% Ag-Co3O4 has good selectivity for toluene at 180 °C. And the response of 16 at% Ag-Co3O4 to 100 ppm toluene reached 2113% with a detection limit 100 ppb. This work provides a novel insight into the toluene sensing mechanism, aiding the design of high-performance toluene sensors.

Study of bismuth metal organic skeleton composites with photocatalytic antibacterial activity

A composite based on Ag and carbon quantum dot (CQDs) doped bismuth metal organic framework (CAU-17) was synthesized by a one-step thermal solvent in situ growth. The microstructure, chemical composition, morphology, photogenerated electron-hole pairs, and photocatalytic activity of the composite were characterized. The produced composite with its unique energy band structure, enhances the visible light absorption and effectively delays the recombination of the photogenerated carriers. On the other hand, the modification with CQDs increases the concentration and transport rate of photogenerated carriers mainly attributed to their superior electron transport capacity and light trapping ability. The photocatalytic antibacterial effect of CAU-17/Ag/CQDs against common Gram-positive, Gram-negative bacteria (Staphylococcus aureus, Escherichia coli) and drug-resistant bacteria (methicillin-resistant Staphylococcus aureus), as well as its inhibition against HepG2 tumor cell were investigated. The results showed that CAU-17/Ag/CQDs exhibited a photocatalytic antibacterial effect with an inactivation rate as high as 99.9 %. At the low dose (0.2 mg/mL), CAU-17/Ag/CQDs indicated a significant inhibition against bacterial growth 20 min after visible light exposure, whereas at the concentration of 0.5 mg/mL, CAU-17/Ag/CQDs completely killed all the tested bacteria. At the concentration of 0.8 mg/mL, the inhibition rate against HepG2 tumor cells reached 75 %. The excellent photocatalytic property of the as prepared composite contributed to the doping of Ag and CQDs, which fundamentally altered the morphology and energy band distribution. Such a composite can be developed into an effective photocatalytic disinfection system and applied to water purification systems, biofilm rejection, combating different antibiotic resistances, and tumor therapy.

Biomimicking synovial joints trans-scale structured AgQDs/MXene/SiOC achieving macroscale high lubrication and superior wear resistance

Naturally optimized successful synovial joints with lightweight, high load-carrying, ultra-low friction and wear have attracted tribological communities to constantly imitate and replicate. Despite impressive advances in cartilage lubrication, extending such extraordinary performance advantages to macroscale solid lubrication remains a challenge. Herein, inspired by the fascinating interplay of synovial joints, a novel kind of trans-scale hierarchical structured ceramic-based composite was developed. Introducing microscale Ag microspheres (AgMs) “cartilage” layer and nanoscale Ag quantum dots/MXene (AgQDs/MXene) “synovial fluid” into the interior and exterior of printed macroscale SiOC “hard bone” realistically restores the gradient structure of synovial joint prototype. The resulted composite with ideal compressive strength (70.44 MPa) can achieve a 60.53% friction reduction and a low wear rate (2.05 × 10−6 mm3 N−1 m−1) in dry tribo-contact for 3600 sliding cycles, while also maintaining considerable low friction (∼ 0.11) over 10,000 sliding cycles and long-term stable lubrication (∼ 0.13) for up to 50,000 reciprocating cycles. Such extraordinary performance can be explained by the division of macro contacts, full loading of AgMs and AgQDs/MXene, abrasive debris capture and removal, as well as the shear rolling effect induced by friction process. This work opens a new avenue to develop structural lubricating materials for complex engineering applications.

Efficient removal for antibiotic-resistant Escherichia coli and antibiotic resistance genes from aquatic environment by BiOCl supported Ag quantum dots

Due to the abuse and difficult removal of antibiotics, how to remove antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARGs) in the environment is facing significant challenges. A series of efficient and non-toxic photocatalytic technologies have been proposed to solve the problem of antibiotic resistance (AR) in wastewater. However, there is limited information on changes in cell behavior and characteristics during photocatalytic processing. In this study, the prepared BiOCl loaded with silver quantum dots was used to treat ARB and ARGs in water, and the physiological characteristics of ARB after photocatalytic treatment were discussed. Using tetracycline (Tet)-resistant and ampicillin (Amp)-resistant Escherichia coli (Tet-E. coli, Amp-E. coli) as target antibiotic resistant bacteria, and using Tet-resistant genes (Tet-RGs) and Amp-resistant genes(Amp-RGs) as target resistance genes, the effects of photocatalyst dosage and silver quantum dot content on photocatalytic performance were studied under UV 365 nm irradiation. The results showed that the optimal inactivation effect was achieved by Ag QDs(500)-BiOCl at a concentration of 300 mg/L, which were 6.91 lg (tet-resistant bacteria) and 6.83 lg (amp-resistant bacteria), respectively. The plasmon resonance effect between the supported silver quantum dots and BiOCl results in the generation of free radicals dominated by holes (h+) and superoxide anions (O2•-) in the system. ARB in the system will be attacked by free radicals, and the permeability of cell membrane gradually increases. For the purpose of protection, the oxidative stress system of cells will first increase the activity of intracellular antioxidant enzymes. Due to the increase of free radicals, antioxidant enzymes gradually become inactive, ultimately leading to cell inactivation. At the same time, after photocatalytic treatment, the absolute abundance of the target resistance gene decreased by 2.79 (tetA) and 3.92 (ampC) lg. Correlation analysis found that inactivation of ARB contributes to the removal of ARGs in the system.

Molecular simulation of Cu, Ag, and Au-decorated Si-doped graphene quantum dots (Si@QD) nanostructured as sensors for SO2 trapping

In view of the numerous environmental hazards and health challenges linked to sulfur (iv) oxide (SO2), an indirect greenhouse gas, and the resultant need to develop efficient gas nanosensor devices, this research had as its principal focus on the theoretical evaluation of the gas sensing potential of metals: Ag, Au and Cu functionalized silicon-doped quantum dots (Si@QD) for the detection and adsorption of SO2 gas investigated using the first-principles density functional theory (DFT) computation at the B3LYP-D3(BJ)/def2-SVP level of theory. Eight (8) possible adsorption modes: SO2_O_Si@QD, SO2_O_Ag_Si@QD, SO2_O_Au_Si@QD, SO2_O_Cu_Si@QD, SO2_S_Si@QD, SO2_S_Ag_Si@QD, SO2_S_Au_Si@QD, and SO2_S_Cu_Si@QD were considered based on SO2 interactions with the studied materials at the -S and -O sites of the SO2 molecule. The counterpoise correction (BSSE) showed that five of the eight interactions had favorable Ead + BSSE values ranging from −0.31 to −1.98 eV. All the eight interactions were observed to be thermodynamically favorable with ΔG and ΔH ranging from −129.01 to −200.24 kcal/mol and −158.26 to −229.73 kcal/mol respectively. Results from the topology analysis reveal that van der Waals forces occurred the greatest at the gas-sensor interphase while SO2_S_ Cu_Si@QD is predicted to have the highest sensing potency based on the conductivity and recovery time estimations. These results confirm the potential efficient feasibility of real-world device application of the metals (Ag, Au, Cu) functionalized Si-doped QDs.

Ag quantum dots decorated ultrathin g-C3N4 nanosheets for boosting degradation of pharmaceutical contaminants: Insight from interfacial electric field induced by local surface plasma resonance

The design of photocatalysts that can generate local surface plasmon resonance effect (LSPR) is expected to be an effective strategy for improving photocatalytic activity. However, the photocatalytic mechanism of interfacial electric field induced by quantum dot plasma is still unclear. Herein, different amount of Ag quantum dots was loaded on ultrathin carbon nitride sheets (Ag/UCN) to construct Schottky junction. The 1:1 Ag/UCN Schottky junction exhibits excellent photocatalytic activity in ofloxacin degradation with 95.2% removal, and is highly stable during four consecutive photocatalytic cycles. Ag/UCN can also effectively mineralize ofloxacin with 65.8% TOC removal, and NH4+, F− and NO3− were detected in the degradation solution of ofloxacin. Moreover, Ag/UCN shows high antibacterial activity and is effective in pharmaceutical wastewater treatment. The enhanced visible-light absorption of Ag/UCN nanocomposites is attributed to the LSPR effect of Ag quantum dots. Finite difference time domain (FDTD) simulations, density functional theory (DFT) calculations and surface potential confirm that the interfacial electric field drives the photogenerated carriers to cross the Schottky barrier, thus effectively accelerating the electron transfer rate at Ag/UCN interface. The photocatalytic mechanism of the interfacial electric field induced by LSPR effect was also revealed, which provides a new insight for design of LSPR-promoted photocatalyst with interfacial electric field induced by quantum dots.

Enhancement of bifunctional photocatalytic activity of boron-doped g-C3N4/SnO2 heterojunction driven by plasmonic Ag quantum dots

Enhancement of photocatalytic charge transfer with reduced electron–hole (e− + h+) recombination toward the targeted chemical reaction is a challenging task. In this study, we utilized boron (B) dopant as impurity levels, and the plasmonic Ag quantum dots (QDs), and g-C3N4/SnO2 heterojunction nanocomposite under visible light (λ = 385–740 nm) as a nanocomposite photocatalytic system for energy and environmental applications. The introduction of B dopant with optimal level (BCN1.0) of 1 wt% resulted in the fast migration of photoexcited electrons from valence band to the conduction band of g-C3N4 and reduced the migration distance of the electrons from valence band to the conduction band and improved surface redox reactions. The heterojunction formed with SnO2 nanorods and nanoparticles enhanced the electron–hole transfer rate across the interface of the heterojunction (BCNS15) with 15 wt% and improved the photocatalytic activity during redox reactions. The introduction of plasmonic Ag QDs (1 wt%) as a co-catalyst improved the H2 generation efficiency (BCNS–Ag1.0). Ultraviolet photoelectron spectroscopy results confirmed that the charge transfer process was initiated via the Z-scheme mechanism. Photoluminescence spectra identified the reduction of electron–hole recombination that was responsible for improved catalytic efficiency in the optimized heterojunction nanocomposite. The synergetic effect of B dopant, the visible light sensitization effect and the co-catalytic effect of the Ag QDs, the formation of a heterojunction of the B-g-C3N4/SnO2/Ag (BCNS–Ag1.0) nanocomposite resulted in 2.5 times higher methyl orange dye degradation efficiency which is 65.6% compared to pristine g-C3N4 (CN) 25.9%. Further, the photocatalysts were tested for photocatalytic H2 generation, the optimized BCNS–Ag1.0 nanocomposite heterojunction showed 3.2 times higher H2 generation activity (10.2 mmol/h/gcat) than pristine CN(3.1 mmol/h/gcat) through Z-scheme mechanism. Finally, the BCNS–Ag1.0 nanocomposite demonstrated excellent stability toward methyl orange degradation as well as H2 generation for at least 4 cycles. Therefore, the BCNS–Ag1.0 nanocomposite is a promising photocatalytic system for scale-up synthesis.