Controllable Silver Release for Efficient Treatment of Drug-Resistant Bacterial-Infected Wounds.

The use of traditional Ag-based antibacterial agents is usually accompanied by uncontrollable silver release, which makes it difficult to find a balance between antibacterial performance and biosafety. Herein, we prepared a core-shell system of ZIF-8-derived amorphous carbon-coated Ag nanoparticles (Ag@C) as an ideal research model to reveal the synergistic effect and structure-activity relationship of the structural transformation of carbon shell and Ag core on the regulation of silver release behavior. It is found that Ag@C prepared at 600 °C (AC6) exhibits the best ion release kinetics due to the combination of relatively simple shell structure and lower crystallinity of the Ag core, thereby exerting stronger antibacterial properties (>99.999 %) at trace doses (20 µg mL-1) compared with most other Ag-based materials. Meanwhile, the carbon shell prevents the metal Ag from being directly exposed to the organism and thus endows AC6 with excellent biocompatibility. In animal experiments, AC6 can effectively promote wound healing by inactivating drug-resistant bacteria while regulating the expression of TNF-α and CD31. This work provides theoretical support for the scientific design and clinical application of controllable ion-releasing antibacterial agents.

Mechanisms of Lanthanum-mediated mitigation of salt stress in soybean (Glycine max L.).

Salinity is considered one of the abiotic stresses that have the greatest impact on soybean production worldwide. Lanthanum (La) is a rare earth element that can reduce adverse conditions on plant growth and productivity. However, the regulatory mechanism of La-mediated plant response to salt stress has been poorly studied, particularly in soybeans. Therefore, our study investigated the mechanisms of La-mediated salt stress alleviation from the perspectives of the antioxidant system, subcellular structure, and metabolomics responses. The results indicated that salt stress altered plant morphology and biomass, resulting in an increase in peroxidation, inhibition of photosynthesis, and damage to leaf structure. Exogenous La application effectively promoted the activity of superoxide dismutase (SOD) and peroxidase (POD), as well as the soluble protein content, while decreasing the Na+ content and Na+/K+ ratio in roots and leaves, and reducing oxidative damage. Moreover, transmission electron microscopy (TEM) demonstrated that La prevented the disintegration of chloroplasts. Fourier-transform infrared spectroscopy (FTIR) analysis further confirmed that La addition mitigated the decline in protein, carbohydrates, and pectin levels in the leaves. Lanthanum decreased the leaf flavonoid content and synthesis by inhibiting the content of key substances in the phenylalanine metabolism pathway during NaCl exposure. Collectively, our research indicates that La reduces cell damage by regulating the antioxidant system and secondary metabolite synthesis, which are important mechanisms for the adaptive response of soybean leaves, thereby improving the salt tolerance of soybeans.

Differential response of proline metabolism defense, Na+ absorption and deposition to salt stress in salt-tolerant and salt-sensitive rapeseed (Brassica napus L.) genotypes.

Soil salinization is a major abiotic factor threatening rapeseed yields and quality worldwide, yet the adaptive mechanisms underlying salt resistance in rapeseed are not clear. Therefore, this study aimed to explore the differences in growth potential, sodium (Na+) retention in different plant tissues, and transport patterns between salt-tolerant (HY9) and salt-sensitive (XY15) rapeseed genotypes, which cultivated in Hoagland's nutrient solution in either the with or without of 150 mM NaCl stress. The results showed that the inhibition of growth-related parameters of the XY15 genotype was higher than those of the HY9 in response to salt stress. The XY15 had lower photosynthesis, chloroplast disintegration, and pigment content but higher oxidative damage than the HY9. Under NaCl treatment, the proline content in the root of HY9 variety increased by 8.47-fold, surpassing XY15 (5.41-fold). Under salt stress, the HY9 maintained lower Na+ content, while higher K+ content and exhibited a relatively abundant K+/Na+ ratio in root and leaf. HY9 also had lower Na+ absorption, Na+ concentration in xylem sap, and Na+ transfer factor than XY15. Moreover, more Na+ contents were accumulated in the root cell wall of HY9 with higher pectin content and pectin methylesterase (PME) activity than XY15. Collectively, our results showed that salt-tolerant varieties absorbed lower Na+ and retained more Na+ in the root cell wall (carboxyl group in pectin) to avoid leaf salt toxicity and induced higher proline accumulation as a defense and antioxidant system, resulting in higher resistance to salt stress, which provides the theoretical basis for screening salt resistant cultivars.

Single substrate-functionalized molybdenum oxide nanozyme for specific colorimetric monitoring of xanthine oxidase activity.

Xanthine-functionalized molybdenum oxide nanodots (X-MoO3-x NDs) with peroxidase (POD)-like activity were developed for selective, sensitive, and facile colorimetric quantification of xanthine oxidase (XO). Xanthine functionalization can not only be favorable for the successful nanozyme preparation, but also for the specific recognition of XO as well as the simultaneous generation of hydrogen peroxide, which was subsequently transformed into hydroxyl radical to oxidize the chromogenic reagent based on the POD-like catalysis. Under the optimized conditions, the colorimetric biosensing platform was established for XO assay without addition of further substrates, showing good linearity relationship between absorbance difference (ΔA) and XO concentrations in the range 0.05-0.5 U/mL (R2 = 0.998) with a limit of detection (LOD) of 0.019 U/mL. The quantification of XO occurs in 25 min, which is superior to the previously reported and commercial XO assays. The proposed method has been successfully used in the assay of human serum samples, showing its high potential in the field of clinical monitoring.

To Love and to Kill: Accurate and Selective Colorimetry for Both Chloride and Mercury Ions Regulated by Electro-Synthesized Oxidase-like SnTe Nanobelts.

Herein, SnTe nanobelts (NBs) with efficient oxidase-mimetic activity were synthesized by the simple electrochemical exfoliation method. A specific inhibition effect of Cl- on the enzymatic behavior of the pure SnTe NBs was discovered, which was accordingly used for establishing a highly feasible, sensitive, selective, and stable Cl- colorimetric assay. The detection concentration range was 50 nM to 1 mM, and the lowest detection limit was 20 nM for Cl-. In addition, a signal on-off-on route based on the SnTe NB nanozyme was designed to realize the reliable and specific detection of Hg2+. Therein, the SnTe NBs were grafted with gold nanoparticles to form a hybrid of SnTe/Au, resulting in the depression of the oxidase-like activity, which can then be recovered in the presence of the Hg2+ due to the formation of a gold amalgam. Especially, it was found that the high concentration of Cl- over 3 mM could again exert suppression influence toward the enzymatic activity of the SnTe/Au-Hg system. Based on the to-love-and-to-kill interaction between Cl- and Hg2+, the detection range for Cl- can be extended to 40 to 250 mM. In return, the assays of Cl- could avoid in advance its interference toward the accurate Hg2+ assays. We systematically clarified the oxidase-like catalytic mechanism of the SnTe-derived nanozyme systems. The as-proposed colorimetry can be successfully applied in practical samples including the sweat, human serum, or seawater/tap water, relating to cystic fibrosis, hyper-/hypochloremia, or environmental control, respectively.

VO x Quantum Dots with Multienzyme-Mimic Activities and the Application in Constructing a Three-Dimensional (3D) Coordinate System for Accurate Discrimination of the Hydrogen Peroxide over a Broad Concentration Range.

The construction of efficient nanozyme with multienzyme activities in a simple way is vital for the wide biological and chemical applications. Generally, the mimic enzyme activities depend on their sizes, surface states, and materials types. Quantum dots (QDs), one type of zero-dimensional nanomaterials, are much appealing due to their abundant catalytically active surface deficiency. The vanadium oxide (VO x) is one special transition metal oxides possessing different valence states. Inspired by these views, we synthesized VO xQDs herein via a one-pot top-down ethanol-thermal method using bulk VO2 as the precursor. The VO xQDs showed not only oxidase- and peroxidase-like activities in ethanol as the main background solution (ethanol-BGS), but also exhibited additional superoxide dismutase mimetic activity in phosphate buffer solution. Furthermore, the TMB-VO xQDs system in the ethanol-BGS produced three distinct colors in the presence of hydrogen peroxide (H2O2) at three different concentration gradients (10-90 µM, 0.1-10 mM, and 20-100 mM). Accordingly, we constructed a three-dimensional (3D) coordinate system (3D-CS) by using the three variables: the initial velocities, the maximum absorption values and the visual colors of the enzymatic reaction system. As a result, the rapid detection of H2O2 can be achieved while effectively avoiding the faked appearance due to the inhibition effects to the enzymatic system at too high H2O2 concentration. The applicability of the VO xQDs based 3D-CS was further proved via the facile and accurate H2O2 assays in three different practical samples.

pH­responsive nanozyme cascade catalysis: A strategy of BiVO4 application for modulation of pathological wound microenvironment.

Persistent inflammation and bacterial infection commonly occur during the wound healing process, necessitating urgent development of effective strategies for treating drug-resistant bacterial infections. In this study, bismuth vanadate (BiVO4) was successfully synthesized as an antibacterial agent that promotes wound healing. Through In vitro antibacterial experiments, it was observed that the prepared BiVO4 exhibited excellent performance in catalyzing H2O2 to produce hydroxyl radicals (OH) at a lower concentration (0.2 mg mL-1), resulting in significant antibacterial effects against Gram-negative Extended-Spectrum ß-Lactamases-Producing Escherichia coli (ESBL-E. coli) strains. Furthermore, biosafety tests, cell scratch experiments, and ESBL-E. coli infected wound rat model experiments demonstrated high biocompatibility of BiVO4 with a cell survival rate exceeding 85 %. Additionally, BiVO4 promoted the production of vascular endothelial growth factors and fibroblasts migration while contributing to collagen production, effectively facilitating immune reconstruction at the wound site. By integrating peroxidase (POD)-like under acidic conditions (pH 4) and catalase (CAT)-like catalytic activities at under neutral conditions (pH 7), BiVO4 exhibited the ability to activate free radical sterilization and accelerate wound healing by activating O2. Therefore, our findings provide evidence for a dual enzyme regulatory mechanism involving antibacterial properties and promotion of wound tissue reconstruction for potential application in both antibacterial treatment and wound healing.

The potential and prospects of modified biochar for comprehensive management of salt-affected soils and plants: A critical review.

Soil salinization has become a global problem that threatens farmland health and restricts crop production. Salt-affected soils seriously restrict the development of agricultural, mainly because of sodium ion (Na+) toxicity, nutrient deficiency, and structural changes in the soil. Biochar is a carbon (C)-based substance produced by heating typical biomass waste at high temperatures in anaerobic circumstances. It has high cation exchange capacity (CEC), adsorption capacity, and C content, which is often used as a soil amendment. Biochar generally reduces the concentration of Na+ in soil colloids through its strong adsorption, or uses the calcium (Ca) or magnesium (Mg) rich on its surface to exchange sodium ions (Ex-Na) from soil colloids through cation exchange to accelerate salt leaching during irrigation. Nowadays, biochar is widely used for acidic soils improvement due to its alkaline properties. Although the fact that biochar has gained increasing attention for its significant role in saline alkali soil remediation, there is currently a lack of systematic research on biochar improvers and their potential mechanisms for identifying physical, chemical, and biological indicators of soil eco-environment assessment and plant growth conditions affected by salt stress. This paper reviews the preparation, modification, and activation of biochar, the effects of biochar and its combination with beneficial salt-tolerant strains on salt-affected soils and plant growth. Finally, the limitations, benefits, and future needs of biochar-based soil health assessment technology in salt-affected soils and plant were discussed. This article elaborates on the future opportunities and challenges of biochar in the treatment of saline land, and a green method was provided for the integrate control to salt-affected soils.

Defect-Engineering-Mediated Long-Lived Charge-Transfer Excited-State in Fe-Gallate Complex Improves Iron Cycle and Enables Sustainable Fenton-Like Reaction.

Fenton reactions are inefficient because the Fe(II) catalyst cannot be recycled in time due to the lack of a rapid electron transport pathway. This results in huge H2 O2 wastage in industrial applications. Here, it is shown that a sustainable heterogeneous Fenton system is attainable by enhancing the ligand-to-metal charge-transfer (LMCT) excited-state lifetime in Fe-gallate complex. By engineering oxygen defects in the complex, the lifetime is improved from 10-90 ps. The lengthened lifetime ensures sufficient concentrations of excited-states for an efficient Fe cycle, realizing previously unattainable H2 O2 activation kinetics and hydroxyl radical (• OH) productivity. Spectroscopic and electrochemical studies show the cyclic reaction mechanism involves in situ Fe(II) regeneration and synchronous supply of oxygen atoms from water to recover dissociated Fe─O bonds. Trace amounts of this catalyst effectively destroy two drug-resistant bacteria even after eight reaction cycles. This work reveals the link among LMCT excited-state lifetime, Fe cycle, and catalytic activity and stability, with implications for de novo design of efficient and sustainable Fenton-like processes.

Microenvironment-Adaptive Nanozyme for Accelerating Drug-Resistant Bacteria-Infected Wound Healing.

Reactive oxygen species (ROS) are favorable for antibacterial infection but their overproduction results in serious inflammatory response and aggravates the hypoxic state of the wound tissue, which is detrimental to healing stages of proliferation and remodeling. Here, an atomic-dispersion Fe-doped oxygen-deficient molybdenum oxide MoO3- X (ADFM) bifunctional nanozyme, featuring implanted peroxidase-like and enhanced catalase-like activity, is developed for decomposing H2 O2 into strongly oxidizing hydroxyl radicals (•OH) for prevention of bacterial infection and into plentiful O2 for healing stages. Therein, the introduction of Fe into MoO3- X primarily produces an asymmetric electron density difference by elongating the bond length between metal atoms, synchronously stabilizing adsorption of •OH and weakening the adsorption of O2 . ADFM also shows unimaginably high aqueous dispersity and pH-adaptive ROS regulation in the wound microenvironment, both of which are favorable for ADFM to fully exert enzyme-like activity for timely antibacterial and efficient wound-healing action. ADFM thus achieves efficient healing of drug-resistant bacteria-infected wounds in vivo, at an ultralow dosage of 30 µg mL-1 against 106 CFU mL-1 extended spectrum ß-lactamases-producing Escherichia coli, exhibiting a wound-healing efficiency of ≈10 mm2 per day, which sets a benchmark among these noble-metal-free nanozyme-based wound-healing agents.

Insights into the antibacterial mechanism of iron doped carbon dots.

Antibacterial nanomaterials provide promising alternative strategies to combat the bacterial infection due to deteriorating resistance. However, few have been practically applied due to the lack of clear antibacterial mechanisms. In this work, we selected good-biocompatibility iron-doped CDs (Fe-CDs) with antibacterial activity as a comprehensive research model to systematically reveal the intrinsic antibacterial mechanism. Through energy dispersive spectroscopy (EDS) mapping of in situ ultrathin sections of bacteria, we found that a large amount of iron was accumulated inside the bacteria treated with Fe-CDs. Then, combining the data of cell level and transcriptomics, it can be elucidated that Fe-CDs could interact with cell membranes, enter bacterial cells through iron transport and infiltration, increase intracellular iron levels, trigger increased reactive oxygen species (ROS), and lead to disruption of Glutathione (GSH)-dependent antioxidant mechanisms. Excessive ROS further leads to lipid peroxidation and DNA damage in cells, lipid peroxidation destroys the integrity of the cell membrane, and finally leads to the leakage of intracellular substances resulting in bacterial growth inhibition and death. This result provides important insights into the antibacterial mechanism of Fe-CDs and further provides a basis for the deep application of nanomaterials in biomedicine.

Recyclable ferroferric oxide@titanium dioxide@molybdenum disulfide with enhanced enzyme-like activity under visible light for effectively inhibiting the growth of drug-resistant bacteria in sewage.

With the development of social industry and the increase in domestic sewage discharge, pathogenic bacterial contamination in water has become a serious health and environmental problem. It is important to design sewage treatment reagents with effective pathogenic bacterial removal and recyclability. In this work, we developed a nanocomposite, Fe3O4@TiO2@MoS2, with once-for-all effects of photocatalytic, magnetic, and peroxidase-like activities for solving the above-mentioned problems. The loading of MoS2 may cause the band gap of Fe3O4@TiO2 to decrease from 3.11 eV to 2.85 eV, demonstrating increased photocatalytic activity under visible light, based on the synergistic impact of Fe3O4@TiO2 and MoS2. In return, the peroxidase-like activity of Fe3O4@TiO2@MoS2 was significantly higher than that of Fe3O4 and MoS2 alone, resulting in the generation of more hydroxyl radicals (˙OH) for combating the drug-resistant broad-spectrum ß-lactamase-producing Escherichia coli and methicillin-resistant Staphylococcus aureus. The antibacterial mechanism study showed that Fe3O4@TiO2@MoS2 could effectively inhibit bacterial growth by destroying the bacterial biofilm and genome via the peroxidase-like activity as well as photocatalytic activity. In addition, Fe3O4@TiO2@MoS2 has excellent paramagnetic properties, which can achieve magnetic recovery after wastewater treatment. Even after three times of recycling, its antibacterial effect can remain above 98.8%.

Achieving Extreme Pressure Resistance to Liquids on a Super-Omniphobic Surface with Armored Reentrants.

Static repellency and pressure resistance to liquids are essential for high-performance super-omniphobic surfaces. However, these two merits appear mutually exclusive in conventional designs because of their conflicting structural demands: Static liquid repellency necessitates minimal solid-liquid contact, which in turn inevitably undercuts the surface's ability to resist liquid invasion exerted by the elevated pressure. Here, inspired by the Springtail, these two merits can be simultaneously realized by structuring surfaces at two size scales, with a micrometric reentrant structure providing static liquid repellency and a nanometric reentrant structure providing pressure resistance, which dexterously avoids the dilemma of their structural conflicts. The nanometric reentrants are densely packed on the micrometric ones, serving as "armor" that prevents liquids invasion by generating multilevel energy barriers, thus naming the surface as the armored reentrants (AR) surface. The AR surface could repel liquids with very low surface tensions, such as silicone oil (21 mN m-1 ), and simultaneously resist great pressure from the liquids, exemplified by enduring the impact of low-surface-tension liquids under a high weber number (>400), the highest-pressure resistance ever reported. With its scalable fabrication and enhanced performance, our design could extend the application scope of liquid-repellent surfaces toward ultimate industrial settings.

Application of a Cascaded Nanozyme in Infected Wound Recovery of Diabetic Mice.

The emergence of peroxidase (POD)-like nanozyme-derived catalytic therapy has provided a promising choice for reactive oxygen species (ROS)-mediated broad-spectrum antibacterials to replace antibiotics, but it still suffers from limitations of low therapeutic efficiency and unusual addition of unstable H2O2. Considering that the higher blood glucose in diabetic wounds provides much more numerous nutrients for bacterial growth, a cascade nanoenzymatic active material was developed by coating glucose oxidase (GOx) onto POD-like Fe2(MoO4)3 [Fe2(MoO4)3@GOx]. GOx could consume the nutrient of glucose to produce gluconic acid (weakly acidic) and H2O2, which could be subsequently converted into highly oxidative •OH via the catalysis of POD-like Fe2(MoO4)3. Accordingly, the synergistic effect of starvation and ROS-mediated therapy showed significantly efficient antibacterial effect while avoiding the external addition of H2O2 that affects the stability and efficacy of the therapy system. Compared with the bactericidal rates of 46.2-59.404% of GOx or Fe2(MoO4)3 alone on extended-spectrum ß-lactamases producing Escherichia coli and methicillin-resistant Staphylococcus aureus, those of the Fe2(MoO4)3@GOx group are 98.396 and 98.776%, respectively. Animal experiments showed that the as-synthesized Fe2(MoO4)3@GOx could much efficiently promote the recovery of infected wounds in type 2 diabetic mice while showing low cytotoxicity in vivo.

Oxygen Vacancy-Mediated Activates Oxygen to Produce Reactive Oxygen Species (ROS) on Ce-Modified Activated Clay for Degradation of Organic Compounds without Hydrogen Peroxide in Strong Acid.

The treatment of acid wastewater to remove organic matter in acid wastewater and recycle valuable resources has great significance. However, the classical advanced oxidation process (AOPs), such as the Fenton reaction, encountered a bottleneck under the conditions of strong acid. Herein, making use of the oxidation properties of CeAY (CeO2@acid clay), we built an AOPs reaction system without H2O2 under a strong acid condition that can realize the transformation of organic matter in industrial wastewater. The X-ray photoelectron spectroscopy (XPS) proved that the CeAY based on Ce3+ as an active center has abundant oxygen vacancies, which can catalyze O2 to produce reactive oxygen species (ROS). Based on the electron spin-resonance spectroscopy spectrum and radical trapping experiments, the production of •O2- and •OH can be determined, which are the essential factors of the degradation of organic compounds. In the system of pH = 1.0, when 1 mg CeAY is added to 10 mL of wastewater, the degradation efficiency of an aniline solution with a 5 mg/L effluent concentration is 100%, and that of a benzoic acid solution with a 100 mg/L effluent concentration is 50% after 10 min of reaction. This work may provide novel insights into the removal of organic pollutants in a strong acid water matrix.

Silver nanoparticles with vanadium oxide nanowires loaded into electrospun dressings for efficient healing of bacterium-infected wounds.

Silver nanoparticles (AgNPs) have been widely recognised as effective antibacterial materials in textiles for enhancing wound healing. However, high loadings of AgNPs are toxic and expensive. Thus, it is ideal to prepare AgNPs in a favourable nanostructure for stable and effective conjugation with the textile carrier by selecting a reductant and stabiliser that contributes to the antibacterial effect. Here, silver nanoparticles/vanadium oxide nanowires (Ag/VOx NWs) were prepared via a one-step reduction strategy using vanadium oxide quantum dots (VOx QDs) as both the reductant and stabiliser. VOx QDs possess antibacterial properties, which aid in minimising the applied silver content while enhancing bactericidal performance. Silver can self-aggregate into nanoparticles as well as promote the formation of vanadium oxide nanowires (VOx NWs). Accordingly, the Ag/VOx NWs exhibited remarkable antibacterial effects against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The nanowire structure of the Ag/VOx NWs was favourable for effective loading into a sodium alginate (SA) gel fabric to form a wound dressing. The effective loading of Ag/VOx NWs on SA was conducive to the complete dispersion of the bacteriostatic agent and enhanced the antibacterial activity of AgNPs. The wound dressing efficiently suppressed the growth of wound bacteria and promoted wound healing in vivo.

Effect of Tool Coatings on Machining Properties of Compacted Graphite Iron.

Compacted graphite iron (CGI) has become the most ideal material for automotive engine manufacturing owing to its excellent mechanical properties. However, tools are severely worn during processing, considerably shortening their lifespan. In this study, we prepared a series of cemented carbide-coated tools and evaluated their coating properties in cutting tests. Among all tested coatings, PVD coating made of AlCrN (AC) presented with the best surface integrity and mechanical properties, achieving the best comprehensive performance in the coating test. The AC-coated tool also exhibited the best cutting performance at a low speed of 120 m/min, corresponding to a 60% longer cutting life and the lowest workpiece surface roughness relative to other coated tools. In the cutting test at a high speed of 350 m/min, the CVD double-layer coated tool (MT) with a TiCN inner layer of and an Al2O3 outer layer had a 70% longer cutting life and the lowest workpiece surface roughness relative to other coated tools.

Heterogeneous Fenton-like magnetic nanosphere coated with vanadium oxide quantum dots for enhanced organic dyes decolorization.

The conventional Fenton reaction has played a vital role in the degradation of pollutants. However, this reaction is prone to forming iron mud, which causes secondary pollution. Additionally, most of the Fenton systems are in homogeneous forms and suffer from intrinsically short lifetimes, hydroxyl radicals that have short diffusion distances (OH) and non-recyclability. Herein, using magnetic composites (Fe3O4@SiO2) as the carrier and vanadium oxide quantum dots (VOxQDs) as the catalyst, we developed a renewable, heterogeneous, magnetic Fenton-like system for dye degradation in polluted wastewater. The VOxQDs of less than 10 nm showed large specific surface areas, enhanced surface-exposed active atoms, and low toxicity, which are favourable for developing an efficient Fenton-like system. In addition, owing to the electrostatic adsorption between the as-prepared catalyst and the dye molecules, the distance for OH sterilization and decolorization can be significantly reduced, overcoming the shortcomings of the short oxidation distance of OH. Accordingly, the degradation of dyes can be achieved in five seconds. Furthermore, the catalysts can be effectively separated and recycled based on their magnetic features, while the secondary pollution from both the catalysts and the incompletely degraded dye molecules into the environment can be avoided. In addition, the Fe3O4@SiO2 is able to maintain a superior morphology, and the composite material (VOxQDs/Fe3O4@SiO2) maintains more than 90% of the degradation effects even after eight repeated tests.

Electrochemistry in Carbon-based Quantum Dots.

Electrochemistry belongs to an important branch of chemistry that deals with the chemical changes produced by electricity and the production of electricity by chemical changes. Therefore, it can not only act a powerful tool for materials synthesis, but also offer an effective platform for sensing and catalysis. As extraordinary zero-dimensional materials, carbon-based quantum dots (CQDs) have been attracting tremendous attention due to their excellent properties such as good chemical stability, environmental friendliness, nontoxicity and abundant resources. Compared with the traditional methods for the preparation of CQDs, electrochemical (EC) methods offer advantages of simple instrumentation, mild reaction conditions, low cost and mass production. In return, CQDs could provide cost-effective, environmentally friendly, biocompatible, stable and easily-functionalizable probes, modifiers and catalysts for EC sensing. However, no specific review has been presented to systematically summarize both aspects until now. In this review, the EC preparation methods of CQDs are critically discussed focusing on CQDs. We further emphasize the applications of CQDs in EC sensors, electrocatalysis, biofuel cells and EC flexible devices. This review will further the experimental and theoretical understanding of the challenges and future prospective in this field, open new directions on exploring new advanced CQDs in EC to meet the high demands in diverse applications.

Recognition of the Enzymatically Active and Inhibitive Oxygenous Groups on WO3-x Quantum Dots by Chemical Deactivation and Density Functional Theory Calculations.

The design and construction of efficient nanozymes are vital for bio/chemo-sensing applications, while the systematic catalytic mechanism study is the prerequisite. Tungsten oxide (WO3-x) quantum dots (QDs), an alternative to conventional heavy metal-containing semiconductor QDs, possess peroxidase-like activity but limited catalytic efficiency. Therefore, the functions of the typical oxygenous groups in determining the enzymatic activity of the WO3-x QDs by target-specifically shielding the carboxyl (-COOH), hydroxyl (-OH), or carbonyl (-C═O) groups, respectively, using a chemical titration method. The results show that the -C═O groups could accelerate the nanozymatic catalysis kinetically, while the -OH ones were the catalytically inhibitive sites, which were further corroborated by the density functional theory (DFT) computations. The application potential of the WO3-x derivatives with an enhanced catalytic ability was verified via the colorimetric cholesterol sensing. The proposed method based on the benzoic anhydride (BA)-modified WO3-x QDs with deactivated -OH groups showed a wider linear range and higher sensitivity than those based on the unmodified ones.