Copper-cobalt dual-site on N-doped carbon nanotube with dual-promoted synergy for glucose electrochemical detection.

Doping specific active sites and accelerating the decisive step of glucose catalysis to construct highly active glucose sensing electrochemical catalysts remains a major challenge for glucose sensing. Herein, we report the detailed design of Cu-Co dual active site N-doped carbon nanotube (CuCo-NCNTs) obtained by electrodeposition modification, programmed warming and calcination for electrochemical glucose detection. In the CuCo-NCNTs material system, Cu serves as the main active site for glucose sensing. Co with good adsorption of hydroxyl groups acts as the site providing hydroxyl groups to provide oxygen source for Cu oxidized glucose sensing. The synergistic effect between the two active sites in the Cu-Co system and the abundant micro-reactive sites exposed by carbon nanotubes greatly ensure the excellent electrocatalytic performance of glucose oxidation reaction. Therefore, CuCo-NCNTs have good electrocatalytic performance with a sensitivity of 0.84 mA mM-1 cm-2 and a detection limit of 1 µM, and also have excellent stability and specificity. DFT calculations elucidate the decisive steps of H-atom removal in the oxidation of glucose by Cu active site N-doped carbon nanotube (Cu-NCNTs) and Co active site N-doped carbon nanotube (CuCo-NCNTs) materials, illustrating the role of oxygen source provided by hydroxyl group adsorption in the electrochemical sensing process of glucose, thus demonstrating that the electrochemical sensing signal of glucose can be effectively enhanced when cobalt species that readily adsorb hydroxyl groups are introduced into the materials.

Fluorometric "AND" logic gate for detection of tyramine and tyrosinase based on in-situ formation of silicon-containing nanoparticles.

BACKGROUND: Tyramine is an important index of food freshness degree, and tyrosinase that can specifically oxidized monophenolamine to catecholamine plays a crucial part in the occurrence and development of melanin-related skin diseases. Therefore, it is crucial to develop sensitive and efficient methods for the detection of tyramine and tyrosinase. RESULTS: In this work, encouraged by tyrosinase-triggered specific oxidation of tyramine to dopamine and the unique fluorescent reaction between dopamine and amino silane, we have developed a one-step synthetic strategy of silicon containing nanoparticles (Si CNPs) for "turn-on" detection of tyramine and tyrosinase. The Si CNPs formed with thoroughly studied mechanism exhibit uniform structure and robust yellow-green fluorescence. The low detection limits for tyramine (1.87 µM) and tyrosinase (0.0029 U/mL) demonstrate admirable sensitivity outstripping most methods. The proposed assay achieves satisfactory results in the determination of tyramine and tyrosinase activity in real samples. Furthermore, we leverage this new fluorescent assay to enable the fabrication of an "AND" Boolean logic gate. SIGNIFICANCE: The entire process can be completed at easily available temperature and pressure with rapid response, convenient operation and visual observation. This fluorescent assay featured with excellent sensitivity, selectivity and stability has considerable prospects in the application of biosensors and disease diagnosis.

Natural Enzyme-Inspired Design of the Single-Atom Cu Nanozyme as Dual-Enzyme Mimics for Distinguishing Total Antioxidant Capacity and the Ascorbic Acid Level.

Although various oxidase mimetic or peroxidase (POD) mimetic nanozymes have been extensively studied, their poor substrate selectivity significantly inhibits their practical applications. Nanozymes with specific biomolecules as substrates, especially ascorbic acid oxidase (AAO) mimetic nanozymes with ascorbic acid (AA) as a substrate, have scarcely been studied. Herein, inspired by the multi-Cu atom sites and the redox electron transfer pathway of Cu2+/Cu+ in the natural AAO, atomically dispersed Cu sites immobilized on N-doped porous carbon (Cu-N/C) are artificially designed to simulate the function of natural AAO. Compared with their natural counterparts, the Cu-N/C catalysts exhibited higher catalytic efficiency and superior stability. Combined theoretical calculation and experimental characterizations reveal that the Cu-N/C nanozymes could catalyze the AA oxidation through a 2e- oxygen reduction pathway with H2O2 as the product. Moreover, the Cu-N/C nanozymes also possess high POD activity. As a proof-of-concept application, Cu-N/C can simultaneously realize AA detection in fluorescent mode based on its AAO activity and total antioxidant capacity detection in colorimetric mode utilizing its POD activity.

Enhanced biomimetic catalysis via self-cascade photocatalytic hydrogen peroxide production over modified carbon nitride nanozymes for total antioxidant capacity evaluation.

The peroxidase mimics usually requires the addition of exogenous hydrogen peroxide (H2O2), which greatly hinder their practical applications. Herein, through rational co-modification of multiple elements (potassium (K), chlorine (Cl) and iodine (I)), the modified carbon nitride nanomaterials (KCl/KI-CN) could serve as efficient bifunctional catalysts. The multiple elements doping and the incorporation of cyano groups (CN) are deemed to enhance their photocatalytic and peroxidase-like activity, respectively. Based on the photocatalytic function, H2O2 can be produced continuously and steadily via two-electron oxygen reduction over modified carbon nitride under visible light irradiation. Subsequently, the KCl/KI-CN could catalyze the chromogenic substrate by the in-situ produced H2O2. Taking advantage of the bifunctional properties of modified carbon nitride, we for the first time demonstrate a self-cascade catalytic process and apply successfully for the ascorbic acid (AA) detection and versatile total antioxidant capacity (TAC) evaluation. This paper not only prepares an efficiently bifunctional catalyst but also provides a new self-cascade photocatalytic H2O2 production strategy for the peroxidase-like application.

Alkaline liquid-derived NaxTi11.5MoVOx/C-40 material with controlled electron transfer rate for sensitive electrochemical detection of dopamine.

The neurotransmitter dopamine (DA) is associated with many physiological and pathological processes, so the importance of low detection limits and high sensitivity analysis cannot be overstated, especially for early disease detection. Here, 2 M NaOH aqueous solution is used to precipitate metal ions in an ethanol solution containing carbon black (CB), and then nanocomposite catalysts (NaxTi11.5MoVOx/C-40 (40 denoted as 40 mg CB)) were obtained by calcining the precipitation. When used for DA detection, NaxVOx acts as the main active site for electrochemical oxidation of DA and NaxTi11.5MoOx plays a role in facilitating the binding of DA to the active site and stabilizing the active site. The NaxTi11.5MoVOx/C-40 electrochemical biosensor has a limit of detection (LOD) of 0.003 µM with a linear range of 0.005-51.665 µM for DA. This sensor can be used to sensitively identify the concentration of DA in human blood and urine. Catalysts containing varying amounts of CB exhibit diverse electron transfer rates, and surprisingly, we found that the appropriate electron transfer rate is optimal for the detection of low concentrations of DA. Because the performance of the electrochemical biosensors is affected by both the activity of the catalysts and the accuracy of the electrochemical testing instrumentation. To better explain this phenomenon, we propose the concept of resolution (Rn) and present the formula to derive it, offering a new approach to evaluating the performance of electrochemical biosensors.

Ultrathin porous PdCu metallenezymes as oxidase mimics for colorimetric analysis.

Ultrathin porous and highly curved two-dimensional PdCu alloy metallene are shown to be highly efficient oxidase mimics. Serving as intrinsic oxidase mimic, the ultrathin porous structure of the PdCu metallenezymes could effectively utilize all the Pd atoms of the metallenezymes during catalytic reactions. By using the oxidation capability of 3,3'5,5'-tetramethylbenzidine as distinctive chromogenic substrate, the PdCu metallenezymes was used as oxidase-like mimics for determination of total antioxidant capacity (TAC) of vitamin C containing real products including fresh orange juice, commercial beverages, Vitamin C tablets and dermo-cosmetic products. AAP was hydrolyzed using ALP to generate AA and the corresponding ALP activity was successfully detected in the 0-100 U/L range with a lowest detection limit of 0.9 U/L. This study demonstrates the significant catalytic performance and oxidase-like activity of PdCu metallene nanozyme providing a strategy to develop a TAC assay for the assessment of antioxidant food quality as well as oxidative stress in skin and health care products.

Single-atom Fe nanozymes with excellent oxidase-like and laccase-like activity for colorimetric detection of ascorbic acid and hydroquinone.

Although traditional Fe-based nanozymes have shown great potential, generally only a small proportion of the Fe atoms on the catalyst's surface are used. Herein, we synthesized single-atom Fe on N-doped graphene nanosheets (Fe-CNG) with high atom utilization efficiency and a unique coordination structure. Active oxygen species including superoxide radicals (O2•-) and singlet oxygen (1O2) were efficiently generated from the interaction of the Fe-CNG with dissolved oxygen in acidic conditions. The Fe-CNG nanozymes were found to display enhanced oxidase-like and laccase-like activity, with Vmax of 2.07 × 10-7 M∙S-1 and 4.54 × 10-8 M∙S-1 and Km of 0.324 mM and 0.082 mM, respectively, which is mainly due to Fe active centers coordinating with O and N atoms simultaneously. The oxidase-like performance of the Fe-CNG can be effectively inhibited by ascorbic acid (AA) or hydroquinone (HQ), which can directly obstruct the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). Therefore, a direct and sensitive colorimetric method for the detection of AA and HQ activity was established, which exhibited good linear detection and limit of detection (LOD) of 0.048 µM and 0.025 µM, respectively. Moreover, a colorimetric method based on the Fe-CNG catalyst was fabricated for detecting the concentration of AA in vitamin C. Therefore, this work offers a new method for preparing a single-atom catalyst (SAC) nanozyme and a promising strategy for detecting AA and HQ.

Ultrathin porous Pd metallene as highly efficient oxidase mimics for the colorimetric detection of chromium (VI).

Palladium (Pd)-based nanomaterials are the emerging class of catalysts with individual physiochemical properties. Unlike traditional catalysts, metallenes showed abundant active sites, large surface area, and high atomic utilization. Based on these benefits, we demonstrate a highly active 2D graphene-like Pd metallene with abundant accessible active sites serving as a highly efficient oxidase mimic. The structure and morphology of Pd metallenezymes were controlled to enhance the catalytic performance and to efficiently utilize all the Pd atoms. Pd metallenezymes with excellent oxidase-like activity were successfully applied for colorimetric-based chromium (VI) (Cr(VI)) detection in a real environment. 3,3',5,5'-Tetramethylbenzidine (TMB) was used as a typical chromogenic substrate catalyzed by Pd metallene to show that blue oxidized TMB (ox TMB) was significantly reduced to colorless TMB by the reducing agent 8-hydroxyquinoline (8-HQ). The reaction process was impressively reversed by the addition of Cr(VI), which interacted with 8-HQ to restore the blue color of TMB. Based on the above results, a facile and effective colorimetric sensing system for the detection of Cr(VI) with a low detection limit of 2.8 nM was developed and could be successfully applied to the detection of Cr(VI) in a real environment.

Effect of different synthesis methodologies on the adsorption of iodine.

Radioactive nuclides such as cesium, ruthenium, and iodine are difficult to remove in radioactive wastewater, which could be removed by coprecipitation of special chemical precipitants. In this study, dynamic Cu/Ag-mordenite (Cu/Ag-MOR) material was synthesized to be treated as the precipitant to selectively adsorb the iodine ion (I-) through controlled chemisorption combined with physical adsorption. XRD, XPS, and FTIR characterization demonstrated the successful modification of the MOR carrier surface by Cu/Ag particles and the high selectivity of the active component Cu (I) on the dynamic Cu/Ag-MOR material. SEM, TEM, and BET methods were used to characterize the Cu/Ag-MOR material, demonstrating these results: the MOR carried a stable porous structure, which allowed the silver to be well dispersed on its surface. The silver improved the copper distribution by being well-coated by the copper species. Furthermore, the analysis of the factors influencing the chemical plating of copper showed that the pH, the concentration of EDTA-2Na and the temperature all influenced the deposition rate of Cu2O. The activation energy for Cu2O deposition in dynamic Cu/Ag-MOR was 20.31 kJ/mol. The highest removal of I- in the presence of dynamic Cu/Ag-MOR could reach 99.1% in the adsorption tests. The adsorption kinetics was under a proposed second-order model, with chemisorption being the controlling step of the reaction. The adsorption/desorption experiments demonstrated the reusability of the nano-sorbent. It was also demonstrated that dynamic Cu/Ag-MOR materials showed good applicability in complex situations where multiple pollutants co-exist.

Cobalt-Nitrogen Co-Doped Carbon as Highly Efficient Oxidase Mimics for Colorimetric Assay of Nitrite.

Transition metal-N-doped carbon has been demonstrated to mimic natural enzyme activity; in this study, cobalt-nitrogen co-doped carbon (Co-N-C) nanomaterial was developed, and it could be an oxidase mimic. Firstly, Co-N-C with oxidase-like activity boosts the chromogenic reaction of 3,3',5,5'-tetramethylbenzidine (TMB) to produce the oxidized TMB (oxTMB). And the aromatic primary amino group of oxTMB reacts with nitrite (NO2-) to form diazo groups. Based on this background, we developed a cascade system of a Co-N-C-catalyzed oxidation reaction and a diazotization reaction for nitrite determination. The low detection limit (0.039 µM) indicates that Co-N-C is superior compared with the vast majority of previously reported nitrite assays. This study not only provides a novel nanozyme with sufficiently dispersed active sites, but it also further applies it to the determination of nitrite, which is expected to expand the application of nanozymes in colorimetric analysis.

Fluorescence detection of 4-nitrophenol and α-glucosidase activity based on 4-nitrophenol-regulated fluorescence of silicon nanoparticles.

A fluorescence assay for the detection of 4-nitrophenol (4-NP), α-glucosidase (α-Glu) activity and α-Glu inhibitors (AGIs) is developed based on the inner filter effect (IFE), a flexible and simple signal transfer strategy. In this assay, silicon nanoparticles (Si NPs) synthesized under mild and easily accessible conditions are employed as fluorescent indicators. 4-NP efficaciously quenches the fluorescence of Si NPs through the IFE at a very rapid rate, thus achieving 4-NP detection in a mix-to-read manner, which is suitable for on-site detection. The quenching mechanism has been comprehensively studied and confirmed. More significantly, based on the fact that 4-NP can be generated through α-Glu-catalyzed hydrolysis of 4-nitrophenyl-α-D-glucopyranoside (NPG), the fluorescence detection of α-Glu activity is legitimately achieved by employing NPG as the substrate. The linear ranges for 4-NP and α-Glu activity detection are 0.5-60 µM and 0.5-60 mU mL-1 with low detection limits of 0.074 µM and 0.094 mU mL-1, respectively. This method not only can preciously assay targets in real samples, but is also capable of screening AGIs as drugs as well as assessing their inhibition efficiency.

A Forceful "Dendrite-Killer" of Polyoxomolybdate with Reusability Effectively Dominating Dendrite-Free Lithium Metal Anode.

In this work, a series of Mo-containing polyoxometalates (POMs) modified separators to inhibit the growth of lithium dendrites, and thus improving the lifespan and safety of the cells is proposed. When the deposited lithium forms dendrites and touches the separator, the optimized Dawson-type POM of (NH4 )6 [P2 Mo18 O62 ]·11H2 O (P2 Mo18 ) with the stronger oxidizability, acts like a "killer", is more inclined to oxidize Li0 into Li+ , thus weakening the lethality of lithium dendrites. The above process is accompanied by the formation of Lix [P2 Mo18 O62 ] (x = 6-10) in its reduced state. Converting to the stripping process, the reduced state Lix [P2 Mo18 O62 ] (x = 6-10) can be reoxidized to P2 Mo18 , which achieves the reusability of P2 Mo18 functional material. Meanwhile, lithium ions are released into the cell system to participate in the subsequent electrochemical cycles, thus the undesired lithium dendrites are converted into usable lithium ions to prevent the generation of "dead lithium". As a result, the Li//Li symmetrical cell with P2 Mo18 modified separator delivers exceptional cyclic stability for over 1000 h at 3 mA cm-2 and 5 mAh cm-2 , and the assembled Li-S full cell maintains superior reversible capacity of 600 mAh g-1 after 200 cycles at 2 C.

Malathion detection based on polydopamine enhanced oxidase-mimetic activity of palladium nanocubes.

Nowadays, fabricating simple and efficient pesticide detection methods become a research focus due to the great threat pesticide residues posed to human health and environment. Herein, we constructed a high-efficiency and sensitive colorimetric detection platform for malathion detection based on polydopamine-dressed Pd nanocubes (PDA-Pd/NCs). The Pd/NCs coated with PDA exhibited excellent oxidase-like activity, which was attributed to the substrates accumulation and accelerated electron transfer induced by PDA. What's more, we successfully achieved sensitive detection of acid phosphatase (ACP) using 3,3',5,5'-tetramethylbenzidine (TMB) as the chromogenic substrate, relying on the satisfactory oxidase activity from PDA-Pd/NCs. However, the addition of malathion could inhibit the activity of ACP and limit the production of medium AA. Therefore, we constructed a colorimetric assay for malathion based on PDA-Pd/NCs + TMB + ACP system. The wide linear range (0-8 µM) and low detection limit (0.023 µM) indicate excellent analytical performance, which is superior to most malathion analysis methods previously reported. This work not only provides a new idea for dopamine coated nano-enzyme to improve its catalytic activity, but also creates a new tactics for the detection of pesticides such as malathion.

Regulating the N Coordination Environment of Co Single-Atom Nanozymes for Highly Efficient Oxidase Mimics.

Single-atom catalysts with well-defined atomic structures and precisely regulated coordination environments have been recognized as potential substitutes for natural metalloenzymes. Inspired by the metal coordination structure of natural enzymes, we show here that the oxidase-like activity of single-atom Co catalysts greatly depends on their local N coordination around the Co catalytic sites. We synthesized a series of Co single-atom catalysts with different nitrogen coordination numbers (Co-Nx(C), x = 2, 3, and 4) and demonstrated that the oxidase-like activity of single-atom Co catalysts could be effectively tailored by fine-tuning the N coordination. Among the studied single-atom Co catalysts, the Co-N3(C) with three-coordinate N atoms shows the optimum oxygen adsorption structure and robust reactive oxygen species (ROS) generation, thus presenting the preferable oxidase-like catalytic activity. This work facilitates the future development of rational nanozyme designs for targeting reactions at the atomic level.

BSA-stabilized silver nanoclusters for efficient photoresponsive colorimetric detection of chromium(VI).

Hexavalent chromium is a highly toxic substance, which will pose a serious threat to human life and health and the entire ecosystem. Therefore, it is crucial to establish a simple and rapid detection method for hexavalent chromium. In this work, we fabricated bovine serum albumin-stabilized silver nanocluster (BSA-Ag13 NC) which exhibited photoresponsive oxidase-like activity, catalyzing the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to the blue oxidized state TMB (oxTMB) in a short time. Interestingly, 8-hydroxyquinoline (8-HQ) can significantly inhibit the color reaction of TMB oxidation while Cr(VI) can interact specifically with 8-HQ to restore this chromogenic reaction. Based on the above facts, a colorimetric sensing system for detecting Cr(VI) was developed. The sensing system shows a wide linear range, and good selectivity, with a low detection limit of 2.32 nM. Moreover, this sensing system could be successfully applied to the detection of Cr(VI) in lake water, tap water, and sewage with satisfactory results.

In situ formed silicon-based nanoparticles enabled highly efficient dual-mode biosensing of chlorpyrifos.

Chlorpyrifos is widely used in agriculture but their residue is a threat to food safety and human health. The study aims to find an accurate and sensitive detection method for chlorpyrifos. Silicon-based nanoparticles (Si BNPs) with fluorescent and colorimetric dual signals are in-situ formed through the alkaline phosphatase (ALP) triggered reaction. The dual-mode sensor for chlorpyrifos can be facilely fabricated because the existence of chlorpyrifos would inhibit the activity of ALP and thus affect the production of Si BNPs. Under optimal condition, the fluorescence intensity and absorption intensity linearly correlate with the logarithm of chlorpyrifos concentration over wide range of 0.5-5000 ng/mL and 1-5000 ng/mL with low detection limit by the two detection modes, respectively. The dual-mode sensor is further applied to the detection of spiked chlorpyrifos in practical samples with satisfactory recovery, rendering it as a promising candidate to current methodologies for the simple and accurate detection of chlorpyrifos.

Platinum nanoparticles confined in metal-organic frameworks as excellent peroxidase-like nanozymes for detection of uric acid.

High levels of uric acid (UA) in humans can cause a range of diseases, and traditional assays that rely on uric acid enzymes to break down uric acid are limited by the inherent deficiencies of natural enzymes. Fortunately, the rapid development of nanozymes in recent years is expected to solve the above-mentioned problems. Hence, we used a host-guest strategy to synthesize a platinum nanoparticle confined in a metal-organic framework (Pt NPs@ZIF) that can sensitively detect UA levels in human serum. Unlike previously reported free radical-catalyzed oxidation systems, its unique electron transfer mechanism confers excellent peroxidase-like activity to Pt NPs@ZIF. In addition, UA can selectively inhibit the chromogenic reaction of TMB, thus reducing the absorbance of the system. Therefore, using the peroxidase-like activity of Pt NPs@ZIF and using TMB as a chromogenic substrate, UA can be detected directly without relying on natural enzymes. The results showed a relatively wide detection range (10-1000 µM) and a low detection limit (0.2 µM). Satisfactory results were also obtained for UA in human serum. This study with simple operation and rapid detection offers a promising method for efficiently detecting UA in serum.

Efficacy and safety of non-prostanoid prostacyclin receptor agonist for pulmonary hypertension: A meta-analysis.

BACKGROUND: Oral non-prostanoid prostacyclin receptor agonists therapies have been recommended for pulmonary arterial hypertension in many countries. OBJECTIVE: We aimed to evaluate the specific impact of non-prostanoid prostacyclin receptor agonists on pulmonary hypertension and to explore the influence of study characteristics on results. METHODS: PubMed, Embase, and ClinicalTrials.gov were systematically searched from inception to July 12, 2022. Randomized controlled trials comparing non-prostanoid prostacyclin receptor agonists administration with placebo for treating pulmonary hypertension were included. Two researchers independently selected eligible studies, assessed the bias risk and extracted related data. RevMan5.1 was used for performing the statistical analysis and the assessment of bias risk of the enrolled studies. PROSPERO registered number CRD42022304172. RESULTS: Seven trials involving 1727 patients were included. Pooled analyses indicated non-prostanoid prostacyclin receptor agonists significantly reduced clinical worsening events (risk ratio [RR], 0.63; 95% confidence interval [CI], 0.54 to 0.74), increased 6-min walk distance (mean difference [MD], 10 m; 95% CI, 3-17 m), decreased pulmonary vascular resistance (MD, -121 dyn s/cm5; 95% CI, -172 to -69 dyn s/cm5) and increased cardiac index (MD, 0.38 L/min/m2; 95% CI, 0.26-0.50 L/min/m2) compared with the control. No significant differences in all-cause mortality (RR, 0.86; 95% CI, 0.26 to 2.78), NYHA/WHO functional class (RR, 1.16; 95% CI, 0.61 to 2.18), mean pulmonary artery pressure (MD, -0.88 mmHg; 95% CI, -2.20 to 0.44 mmHg), right atrial pressure (MD, 0.66 mmHg; 95% CI, -0.59 to 1.90 mmHg) and total adverse events (RR, 1.05; 95% CI, 0.99 to 1.10) were found between non-prostanoid prostacyclin receptor agonists group and control group. CONCLUSION: Non-prostanoid prostacyclin receptor agonists treatment exerted benefits on clinical worsening, pulmonary vascular resistance, and cardiac index in pulmonary hypertension patients, without increasing the incidence of total adverse events.

Rational design and fabrication of MoSx nanoclusters decorated Mn0.3Cd0.7S nanorods with promoted interfacial charge transfer toward robust photocatalytic H2 generation.

In this work, we report a novel MoSx/Mn0.3Cd0.7S composite catalyst that has been designed and fabricated by in situ coupling MoSx nanoclusters with 1D Mn0.3Cd0.7S nanorods for photocatalytic H2 production. The catalyst features a 1D nanostructure with MoSx nanoclusters uniformly dispersed along the Mn0.3Cd0.7S nanorod. It was found that an intimate interface is built between MoSx nanoclusters and Mn0.3Cd0.7S nanorods thanks to the facile in situ photoreduction route, which contributes to a high-efficiency interfacial charge separation. The resulting MoSx/Mn0.3Cd0.7S photocatalyst shows a dramatically enhanced visible-light-driven photocatalytic H2 production activity compared with the control samples, owing to more efficient spatial charge separation as well as enriched active sites. This work is expected to provide an optimized structure model for rational design and constructing novel, inexpensive, efficient and stable cocatalyst/metal sulfide photocatalyst systems for H2 production.

Self-deposited ultrasmall Ru nanoparticles on carbon nitride with high peroxidase-mimicking activity for the colorimetric detection of alkaline phosphatase.

Carbon nitride (C3N4) nanosheets are known as peroxidase mimics, but the low activity hinders their further application. Embedding active metal nanoparticles onto the C3N4 nanosheets is expected to break this limitation. Herein, highly dispersed ultrasmall Ru nanoparticles are anchored onto the C3N4 through spontaneous redox reaction. The as-obtained Ru-C3N4 exhibits excellent peroxidase-like activity, which can be further regulated by adjusting the loading of Ru nanoparticles on C3N4. Using Ru-C3N4 as a mimetic peroxidase, a colorimetric sensing method for alkaline phosphatase (ALP) detection is developed based on the inhibitory effect of ascorbic acid produced by hydrolysis of ALP and l-ascorbic acid 2-phosphate (AAP) on the color development reaction of TMB catalyzed by Ru-C3N4. The sensor exhibits wide linear range and low detection limit for the ALP sensing. Finally, the assay is applied to ALP detection in human serum and satisfactory results are obtained, which provides a promising strategy for colorimetric sensing of ALP.