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A novel peroxidase-mimic with supported nanostructure, by loading surface-clean IrO 2 clusters on dendritic mesoporous silica nanospheres (DMSNs), exhibited superior peroxidase catalysis via electron transfer, which was utilized for the sensitive detection of acetylcholine esterase and its inhibitor by the colorimetric assays. [Display omitted] Nanomaterials-based enzyme mimics (nanozymes), by simulating enzyme catalysis, have shown potential in numerous biocatalytic applications, but nanozymes face significant challenges of catalytic activity and reusability that may restrict their practical uses. Herein, we report facile fabrication of surface-clean IrO 2 clusters supported on dendritic mesoporous silica nanospheres (DMSNs), which exhibit superior peroxidase-like activity, high thermal/long-term stability, and good recyclability. The IrO 2 clusters (1.4 ± 0.2 nm in size) are obtained by the laser ablation without any ligands and possess negative surface charge, which are efficiently loaded on the amino-functionalized DMSNs by electrostatic adsorption. Owing to morphological and structural advantages, the resulted DMSN/IrO 2 heterostructure displays outstanding peroxidase-like catalytic performance. Compared with horseradish peroxidase, it shows comparable affinities but higher reaction rate (2.95 × 10−7 M·s−1) towards H 2 O 2 , resulting from rapid electron transfer during the catalysis. This value is also larger than those of mesoporous silicas supported metal or metal oxides nanoparticles/clusters in the previous studies. Benefitting from excellent peroxidase-catalysis of the DMSN/IrO 2 , the colorimetric assays are further successfully established for the detection of acetylcholine esterase and its inhibitor, showing high sensitivity and selectivity. The work provides novel design of supported nanozymes for biosensing. [ABSTRACT FROM AUTHOR]

Nanocatalytic therapy, involving the nanozyme‐triggered production of reactive oxygen species (ROS) in the tumor microenvironment (TME), has demonstrated potential in tumor therapy, but nanozymes still face challenges of activity and specificity that compromise the therapeutic efficacy. Herein, we report a strategy based on a single‐atom nanozyme to initiate cascade enzymatic reactions in the TME for tumor‐specific treatment. The cobalt‐single‐atom nanozyme, with Co−N coordination on N‐doped porous carbon (Co‐SAs@NC), displays catalase‐like activity that decomposes cellular endogenous H2O2 to produce O2, and subsequent oxidase‐like activity that converts O2 into cytotoxic superoxide radicals to efficiently kill tumor cells. By incorporation with doxorubicin, the therapy achieves a significantly enhanced antitumor effect in vivo. Our findings show that cascade TME‐specific catalytic therapy combined with chemotherapy is a promising strategy for efficient tumor therapy. [ABSTRACT FROM AUTHOR]

Nanocatalytic therapy, involving the nanozyme‐triggered production of reactive oxygen species (ROS) in the tumor microenvironment (TME), has demonstrated potential in tumor therapy, but nanozymes still face challenges of activity and specificity that compromise the therapeutic efficacy. Herein, we report a strategy based on a single‐atom nanozyme to initiate cascade enzymatic reactions in the TME for tumor‐specific treatment. The cobalt‐single‐atom nanozyme, with Co−N coordination on N‐doped porous carbon (Co‐SAs@NC), displays catalase‐like activity that decomposes cellular endogenous H2O2 to produce O2, and subsequent oxidase‐like activity that converts O2 into cytotoxic superoxide radicals to efficiently kill tumor cells. By incorporation with doxorubicin, the therapy achieves a significantly enhanced antitumor effect in vivo. Our findings show that cascade TME‐specific catalytic therapy combined with chemotherapy is a promising strategy for efficient tumor therapy. [ABSTRACT FROM AUTHOR]

MoS2-based nanocomposites are emerging as novel versatile materials. Here, uniform Pt3Au1 nanoparticles ( NPs) decorated few-layer MoS2 nanosheets were fabricated as novel enzyme mimics. Compared to pure MoS2 nanosheets, the as-prepared MoS2-Pt3Au1 nanocomposites displayed enhanced peroxidase-like activity. The nanocomposites also possessed well dispersibility and high stability in water. With these findings, a simple, fast and low-cost colorimetric detection of phenol with high sensitivity and selectivity is developed, which is based on oxidative coupling reaction of phenol and 4-aminoantipyine in the presence of H2O2 as an oxidant to form pink color products. This work provides a type of MoS2-NP composites as enzyme mimics for many potential applications in catalysis. [ABSTRACT FROM AUTHOR]

Porous Au@Pt nanoparticles (NPs) with electron-rich Pt shells exhibited significantly enhanced peroxidase-like activity by changing the catalytic reaction path, which offered valuable opportunities to construct sensitive colorimetric biosensors, as exemplified by detection of spike 1 protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). [Display omitted] The development of colorimetric assays for rapid and accurate diagnosis of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is of practical importance for point-of-care (POC) testing. Here we report the colorimetric detection of spike (S1) protein of SARS-CoV-2 based on excellent peroxidase-like activity of Au@Pt nanoparticles, with merits of rapidness, easy operation, and high sensitivity. The Au@Pt NPs were fabricated by a facile seed-mediated growth approach, in which spherical Au NPs were premade as seeds, followed by the Pt growth on Au seeds, producing uniform, monodispersed and porous Au@Pt core–shell NPs. The as-obtained Au@Pt NPs showed a remarkable enhancement in the peroxidase-mimic catalysis, which well abided by the typical Michaelis-Menten theory. The enhanced catalysis of Au@Pt NPs was ascribed to the porous nanostructure and formed electron-rich Pt shells, which enabled the catalytic pathway to switch from hydroxyl radical generation to electron transfer process. On a basis of these findings, a colorimetric assay of spike (S1) protein of SARS-CoV-2 was established, with a linear detection range of 10–100 ng mL−1 of protein concentration and a low limit of detection (LOD) of 11 ng mL−1. The work presents a novel strategy for diagnosis of COVID-19 based on metallic nanozyme-catalysis. [ABSTRACT FROM AUTHOR]

Due to low cost and high stability, the applications of inorganic nanomaterials as efficient alternatives to natural enzymes are drawing much attention. In this work, novel CuO/Pt nanocomposites with high peroxidase-like activity were designed and applied for the colorimetric detection of ascorbic acid (AA). The nanocomposites were prepared by decorating Pt NPs on the surface of CuO nanosheets, which displayed good uniformity and showed improved distribution and stability. The catalytic activity of the prepared CuO/Pt nanocomposites was tested against various chromogenic substrates in the presence of H2O2, which displayed efficient peroxidase-like activity and high catalytic stability against temperature. The catalytic mechanism of the CuO/Pt nanocomposites was investigated by hydroxyl radical detection. The peroxidase-like activity decreased significantly in the presence of AA. On the basis of the inhibition property, a colorimetric biosensor was constructed by using the CuO/Pt nanocomposites for the detection of AA. It showed a high selectivity against amino acids, carbohydrates and normal ions. Thus, this work provides new insights into the application of inorganic nanocomposite-based nanozymes in the biosensing field. [ABSTRACT FROM AUTHOR]

The successful synthesis of ruthenium oxide/reduced graphene oxide (RuO2/rGO) heterostructures by one-pot hydrothermal method using graphene oxides and RuCl3 as precursors is reported. The heterostructures had high peroxidase-like (POD-like) activities, which catalyzes the oxidation of classical peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 to create a blue colored reaction product. The catalytic activity was significantly enhanced by the synergistic effect between RuO2 nanoparticles and rGO. RuO2/rGO had a low Km of 0.068 mM and a high vmax of 1.228 × 10−7 M·s−1 towards TMB in the TMB-H2O2 catalytic oxidation system. In addition, the POD-like activity originating from the electron transfer mechanism was confirmed by cytochrome C (Cyt C) oxidation experiment. A colorimetric method based on RuO2/rGO heterostructures was developed with good sensitivity and selectivity for glucose detection with a limit of detection of 3.34 μM and a linear range of 0–1500 μM. The RuO2/rGO heterostructures have potential applications in the biomedical areas, such as biosensor and diagnostics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Noble metal-semiconductor hybrid Au/ZnO nanowires have been fabricated by chemical vapor deposition method. • Compared with ZnO nanowires, Au/ZnO heterostructures exhibited significantly enhanced photocatalytic performance due to the synergistic combination of Au and ZnO. • Optical properties were modeled to support our interpretation of photocatalytic mechanisms. • Our work provides a feasible strategy to prepare plasmonic photocatalysts and will also deepen the understanding of the plasmon enhanced photocatalytic performance in hybrid photocatalysts. Using sunlight as renewable resource has stimulated the development of sustainable photocatalysts that can collect visible light. Semiconductor nanowire-based photocatalysts have attracted increasing interest due to their unique optical, electronic, and structural advantages. Here, noble metal-semiconductor hybrid Au/ZnO nanowires have been fabricated by chemical vapor deposition method. The hybrid photocatalysts were well characterized by SEM, TEM, EDS, XRD, XPS, UV–visible spectroscopy and Raman spectroscopy. Compared with ZnO nanowires, Au/ZnO heterostructures exhibited significantly enhanced photocatalytic performance due to the synergistic combination of Au and ZnO. Optical properties were modeled to support our interpretation of photocatalytic mechanisms. Our work provides a feasible strategy to prepare plasmonic photocatalysts and will also deepen the understanding of the plasmon enhanced photocatalytic performance in hybrid photocatalysts. [ABSTRACT FROM AUTHOR]

Schematic of an electrochemical sensor integrating CuAu/BSA/GA conductive antifouling complex and 3-in-1 dual-targeted aptamer for the detection of SARS-CoV-2 spike protein. [Display omitted] • The economical nanocoating (CuAu/BSA/GA) showed good conductivity and antifouling properties. • A "3-in-1″ aptamer targeting both BSA, SARS-CoV-2 spike protein was designed. • This strategy greatly simplifies the multi-step modification of the biosensor. Electrochemical biosensors have shown promise in bioanalysis and diagnosis. However, they suffer from the accumulation and adhesion of biomolecules in biofluids on sensing surfaces, while the hiring of potential antifouling is limited by the cost and complexity of the construction methods. Here, an economical three-dimensional (3D) conductive antifouling coating was prepared. This coating was composed of bovine serum albumin (BSA) crosslinked glutaraldehyde (GA) and copper-gold nanowires (CuAu NWs) with excellent electrical conductivity. Furthermore, a dual-targeted aptamer (D-Apt), with a "3-in-1″ structure of two specific binding sequences and a DNA linker, was designed to specifically recognize BSA and the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein, affording low nanomolar binding affinity. Importantly, the introduction of the D-Apt greatly simplified the functionalization procedure on the electrode surface and the immobilization of the biorecognition element. Then, a simple electrochemical biosensor based on the CuAu/BSA/GA and D-Apt was constructed for the detection of S protein. This sensor exhibited merits of cost-effectiveness, sensitivity and practicality for detection of S protein. The work could provide a facile avenue to construct electrochemical biosensors with low-cost antifouling for the accurate diagnosis of epidemic antigenic disease markers. [ABSTRACT FROM AUTHOR]

Herein we have identified an optimal catalyst, Pd1Ag1.7, for the tandem reductive amination between nitroarenes and aldehydes (selectivity ＞ 93%). Key to the success is the ability to control the compositions of the investigational Pd1−xAgx (x = 0–1) catalysts, as well as the clear composition dependent activity/selectivity trend observed in this study. This catalyst features a wide substrate scope, excellent recyclability, activity and selectivity under ambient conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Mo 2 C/MoO x films were conveniently fabricated by chemical vapor deposition. • PMS activation and photocatalysis were achieved by the films for TC degradation. • The high degradation efficiency could be maintained after 10 cycles of the films. Advanced oxidation processes (AOPs) based on photocatalysis and peroxymonosulfate (PMS) activation have shown potential in antibiotics degradation by generating series of reactive oxygen species (ROS). However, construction of AOP materials with easy preparation and high reusability is still a challenge. Herein, we prepared a Mo 2 C/MoO x thin film through one-step chemical vapor deposition (CVD), and this film could synergistically promote PMS activation and visible-light photocatalysis due to the redox cycles of multiple Mo valence states and staggered bandgap structures of Mo-based components in the film. The generated oxygen species (mainly 1O 2 radical, accompanying by other ones involving OH, SO 4 − and O 2 − radicals) could efficiently degrade the uneasily degradable antibiotics, tetracycline (TC), with a removal efficiency of 91.7 % within 60 min. Meanwhile, the film could maintain the TC degradation capability for at least 10 cycles, exhibiting promising reusability. The work could provide feasible approaches to develop easily prepared AOP thin film materials for antibiotic pollutant degradation. [ABSTRACT FROM AUTHOR]

Graphical abstract The Rh nanoparticles were prepared by pulsed Laser ablation in ethanol. Then, the obtained Rh nanoparticles were decorated on GO through the electrostatic interaction. Finally, Rh/GO nanocomposites were used to catalyze the reduction of 4-NP into 4-AP in the presence of excess sodium borohydride. Highlights • Green synthesis of ultrafine ligands-free Rh nanoparticles with no byproducts. • Uniformly supported by graphene oxide nanosheets with controllable Rh loading. • Outstanding catalytic activities in catalytic reduction of 4-nitrophenol. Abstract We report a facile and green route to prepare ligand-free ultrafine rhodium (Rh) nanoparticles decorated on graphene oxide (GO) nanosheets. The ultrafine Rh nanoparticles with average size 1.8 ± 0.4 nm were synthesized by pulsed laser ablation in liquid. The Rh nanoparticles could be uniformly supported on the surface of GO through the electrostatic interaction. The reduction of 4-nitrophenol in presence of NaBH 4 was performed as a model reaction to evaluate the catalytic properties of Rh/GO nanocomposites. The Rh/GO nanocomposites showed remarkable high catalytic activities with rapid and complete conversion of 4-nitrophenol to 4-aminophenol. The kinetic constant rate of the Rh/GO nanocomposites was 7.62 × 10−3 s−1, which is 27 times higher than commercial Rh/C catalyst, revealing the high catalytic activity in catalytic hydrogenation. The Rh/GO nanocomposites showed good stability and high catalytic activity due to the small size Rh nanoparticles, uniformly dispersed on GO nanosheets. This work may provide a green and alternative method to prepare ligand-free supported ultrafine noble metal heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Graphical abstract The fabrication process of MoO 3−x nanodots by PLA method. MoO 3−x nanodots exhibited dual enzyme mimic activities and were adopted as multifunctional agents to modulate Aβ assembly. Abstract Development of effective inhibitors toward Aβ aggregation and reactive oxygen species (ROS) scavengers are of crucial therapeutic implications for Alzheimer's disease (AD). Herein, a novel agent with dual enzyme mimic activities has been fabricated as a multifunctional Aβ fibrillation modulator. MoO 3−x nanodots were synthesized by pulsed laser ablation (PLA) method in MoS 2 nanosheets solutions, which may act directly as numerous fine targets. MoO 3−x nanodots showed a uniform and monodispersed morphology, and the tiny dots were around 3–5 nm with a narrow size distribution. Due to the efficient charge transition between Mo5+/Mo6+ on the dots surface, MoO 3−x nanodots exhibited excellent catalase and SOD mimic activities, which were adopted to alleviate Aβ-mediated oxidative stress. Moreover, MoO 3−x nanodots can efficiently inhibit Aβ aggregation and destabilize the preformed fibrils, and eventually protect neuronal cells from apoptosis induced by Aβ. Taken together, MoO 3−x nanodots with multifunctional roles can act as a potential therapeutic strategy for treatment of amyloid induced neurotoxicity. [ABSTRACT FROM AUTHOR]

The continuous evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with discovery of multiple mutants, has caused widespread panic and concern worldwide. The rapid antigen detection method via a single ligand recognition, although currently implemented in many countries, remains challenging for mutated antigens. Herein, we present a novel strategy using a dual recognition by two types of targeted ligands, based on photoelectrochemical (PEC) sensing for detection of SARS-CoV-2 spike protein. To demonstrate this strategy, the specific antibodies are modified onto the photoactive material with a supported nanostructure, created by loading the Pt nanoparticles onto MoS 2 nanosheets (Pt/MoS 2) to boost photon-to-electricity conversion efficiency. By subsequent binding of the targeted aptamers to the Au polyhedra, which act as a signal amplifier to suppress PEC photocurrent by competing with the Pt/MoS 2 for the absorption of excitation light energy, the dual recognition is successfully achieved. The constructed biosensor not only shows satisfactory stability, high sensitivity, and selectivity, but is effective for test of the pseudovirus of SARS-CoV-2. The work provides useful advance for the development of PEC biosensors for sensitive detection of SARS-CoV-2. • Introducing Pt nanoparticles induced formation of more 1T-MoS 2 in Pt/MoS 2. • Pt/MoS 2 showed enhanced conductivity, stability, and photoelectric conversion. • The aptamers-functionalized Au polyhedra acted as an effective signal amplifier. • The sensor gave a low limit of detection (0.53 ng/mL) of S1 protein. [ABSTRACT FROM AUTHOR]

[Display omitted] • MoO x /MoS 2 thin films successfully synthesized by two-step vapor deposition. • The MoO x /MoS 2 thin films having abilities of reducing bacterial adhesion and inactivating bacteria. • The MoO x /MoS 2 nanocomposites having visible-light-driven photocatalytic activity to effectively kill both gram-negative and gram- positive bacteria. • Potential applications of MoO x /MoS 2 nanocomposites for environment purification and pathogenic bacterial treatment. Multifunctional semiconductor nanomaterials have potential for a lot of applications. Recently molybdenum disulfide (MoS 2)-based nanostructures have been attracted much attention. Here, we have successfully fabricated the MoO x /MoS 2 thin films on the silicon wafer by chemical vapor deposition method and demonstrated their applications to reduce bacterial adhesion and to inactivate of bacteria. The as-prepared MoO x /MoS 2 nanocomposites have hydrophobic property and visible-light-driven photocatalytic activity. By applying visible-light irradiation, the ROS production of MoO x /MoS 2 nanocomposites could effectively kill both gram-negative and positive bacteria. The results suggest that the MoO x /MoS 2 nanocomposites may have potential applications for environment purification and pathogenic bacteria treatment. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) has been an intractable neurodegenerative disease among the elderly in the worldwide. One of the important pathogenic factors in AD is the aggregation of amyloid-β 1-42 (Aβ42) in AD patients' brain. Inhibition of Aβ peptide aggregation is considered as one of the effective approaches against AD. Herein, a pulsed laser ablation (PLA) method is used to fabricate ultra-small carbon quantum dots (C-QDs) with uniform size. The reduced Aβ42 aggregation by the C-QDs was confirmed by transmission electron microscopy (TEM), thioflavin T assay and circular dichroism (CD) spectroscopy. The results of cell viability experiments showed that the presence of the C-QDs could significantly reduce the cytotoxicity of Aβ42. Furthermore, in vivo studies demonstrate that C-QDs can decrease Aβ42 deposits and promote the biological activity of an AD model of Caenorhabditis elegans CL2006. This work demonstrates the viability of using ultrasmall C-QDs to inhibit amyloid-β aggregation and alleviate amyloid-β mediated neurotoxicity. [Display omitted] • Ultra-small carbon quantum dots have been successfully synthesized. • Carbon quantum dots can effectively inhibit Aβ42 peptide aggregation. • The cytotoxicity of Aβ42 peptides is reduced by carbon quantum dots. [ABSTRACT FROM AUTHOR]

• Surface-clean Pd-Au nanosheets with high electron mobility and good catalytic performance were synthesized by a simple method. • The detection limit for detecting SARS-CoV-2 spike protein is as low as 0.0072 ng•mL−1 (S/ N = 3). • The combination of Pd-Au nanosheets and functionalized MNPs enhances the sensitivity of the sensor. • The electrochemical immunosensor based on Pd-Au nanosheets has been developed for sensitive antigen detection. Tracking and monitoring of low concentrations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can effectively control asymptomatic transmission of current coronavirus disease 2019 (COVID-19) in the early stages of infection. Here, we highlight an electrochemical immunosensor for sensitive detection of SARS-CoV-2 antigen marker spike protein. The surface-clean Pd-Au nanosheets as a substrate for efficient sensing and signal output have been synthesized. The morphology, chemical states and excellent stable electrochemical properties of this surface-clean heterostructures have been studied. Functionalized superparamagnetic nanoparticles (MNPs) were introduced as sample separators and signal amplifiers. This biosensor was tested in phosphate buffered saline (PBS) and nasopharyngeal samples. The results showed that the sensor has a wide linear dynamic range (0.01 ng mL−1 to 1000 ng mL−1) with a low detection limit (0.0072 ng mL−1), which achieved stable and sensitive detection of the spike protein. Therefore, this immunosensing method provides a promising electrochemical measurement tool, which can furnish ideas for early screening and the reasonable optimization of detection methods of SARS-CoV-2. [Display omitted] [ABSTRACT FROM AUTHOR]

Octahedral Au-Ag nanoframes are prepared by reaction of AgNO3 with CuCl in octadecylamine solution at 115 °C, followed by dropwise addition of HAuCl4 solution (115 °C, 20 min). [ABSTRACT FROM AUTHOR]