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Ce-based nanomaterials have been widely studied as catalyst for their unique electronic structure, but there are few reports on the combination of cerium catalytic activity and photoluminescence performance. In this paper, by adjusting the molar ratio of Ce/P, CeO 2 /CePO 4 nanocrystal were synthesized in one-step, which integrated the enzyme activities of CeO 2 and CePO 4 , as well as the optical property of CePO 4 together. Taking H 2 O 2 as analyte model, utilizing the catalase oxidization activity of CeO 2 /CePO 4 , TMB molecule can be oxidized, leading to the increased absorption intensity of 652 nm, realizing the colorimetric assay of H 2 O 2 . On the other hand, using the fluorescence of CeO 2 /CePO 4 at 338 nm as output signal, which can be quenched by H 2 O 2 since Ce 3+ ions were oxidized into Ce 4+ , realizing H 2 O 2 fluorescence detection. Compared with the single-signal probe, CeO 2 /CePO 4 provides two sensing modes of fluorescence and colorimetry for H 2 O 2 discrimination to obtain different test results, which can be mutually verified and effectively improve the detection accuracy., Competing Interests: Declarations Ethical Approval Not applicable. Supporting Information SEM of samples synthesized at different reaction times under 180℃ with Ce/P ratio of 4:1 (Fig. S1); XPS spectrum of CeO2/CePO4 (Fig. S2); Ce 3d and O1s XPS spectra of CeO2/CePO4 sample (Fig. S3); O1s XPS spectra of samples with different Ce/P molar ratio (Fig. S4); P2p XPS spectra of CeO2/CePO4 (Fig. S5); Steady-state kinetic analysis of CeO2/CePO4 (Fig. S6); Radical species study (Fig. S7); Reaction time study on CeO2/CePO4 enzyme activity (Fig. S8); Selectivity of CeO2/CePO4 toward interfering species (Fig. S9); Stability on the UV-Vis absorption durability of CeO2/CePO4 (Fig. S10); Fluorescence spectra of different samples (Fig. S11); Synthesis time study (Fig. S12); Optical stability study in NaCl solution(Fig. S13); Fluorescence stability study towards storage time (Fig. S14); Study on the percentage of different elements of CeO2/CePO4 (Table S1); Actual serum samples analysis (Table S2). Competing Interests The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

The H 2 production using N 2 H 4 splitting (OHzS) was often constrained by the requirement for insufficient stability, distinct catalysts at the anode and cathode, and the high-cost electrocatalyst associated with confined activity. This work verified the efficacy of surfactant-free branched CuAu nano-alloy as a bifunctional electrocatalyst for H 2 production. Benefiting from its favorable electronic structure and surfactant-free surface, surfactant-free CuAu nano-alloy demonstrated a reduced over-potential compared with pure Cu, pure Au, and CuAu nano-alloy prepared by surfactant. When using branched CuAu nano-alloy as both cathodic and anodic electrodes, a cell voltage of 0.768 V was required to drive a current density of 10 mA/cm 2 . After 2550 min of H 2 generation, the amplitude of the working potential for anodic reactions was found to be less than 0.92%. The enhanced electrocatalytic activity could be also applied to H 2 O 2 and NaNO 2 sensors. The CuAu nano-alloy exhibited a 2.35-folds increase in sensitivity compared to pure Au nano-crystals in the detection of H 2 O 2 . Moreover, the detection of NaNO 2 in water solution has been successfully achieved. The detection range 0-175.0 mM was much wider than that of sensors in previous works., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

The treatment of wound inflammation is intricately linked to the concentration of reactive oxygen species (ROS) in the wound microenvironment. Among these ROS, H 2 O 2 serves as a critical signaling molecule and second messenger, necessitating the urgent need for its rapid real-time quantitative detection, as well as effective clearance, in the pursuit of effective wound inflammation treatment. Here, we exploited a sophisticated 3D Cu 2- x Se/GO nanostructure-based nanonzymatic H 2 O 2 electrochemical sensor, which is further decorated with evenly distributed Pt nanoparticles (Pt NPs) through electrodeposition. The obtained Cu 2- x Se/GO@Pt/SPCE sensing electrode possesses a remarkable increase in specific surface derived from the three-dimensional surface constructed by GO nanosheets. Moreover, the localized surface plasma effect of the Cu 2- x Se nanospheres enhances the separation of photogenerated electron-hole pairs between the interface of the Cu 2- x Se NPs and the Pt NPs. This innovation enables near-infrared light-enhanced catalysis, significantly reducing the detection limit of the Cu 2- x Se/GO@Pt/SPCE sensing electrode for H 2 O 2 (from 1.45 μM to 0.53μM) under NIR light. Furthermore, this biosensor electrode enables in-situ real-time monitoring of H 2 O 2 released by cells. The NIR-enhanced Cu 2- x Se/GO@Pt/SPCE sensing electrode provide a simple-yet-effective method to achieve a detection of ROS (H 2 O 2 、-OH) with high sensitivity and efficiency. This innovation promises to revolutionize the field of wound inflammation treatment by providing clinicians with a powerful tool for accurate and rapid assessment of ROS levels, ultimately leading to improved patient outcomes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Shen, Dai, Ning, Xu, Zhou, Chen, Ren, Chen, Gao and Bao.)

Photoluminescence (PL) spectroscopy is one of the best methods to detect molecules due to its easiness, fast time of analysis and high sensitivity. In addition, zinc oxide (ZnO) possesses good optical properties and particularly PL emission in these materials have been exploited for their potential use as photocatalyst, light harvesting and photosensor. These PL properties enhance when graphene quantum dots (GQD) are added to ZnO. For these reasons, we investigated the PL performance of ZnO-GQD nanocomposites. In one experiment we evaluated the PL emission of solid samples ZnO and ZnO-GQD. In a second experiment, these samples were also evaluated in aqueous phase to investigate the H 2 O 2 effect during an experiment lasting 170 minutes. Both experiments displayed six peaks and they were related to the same PL emission source. The PL emission peak around 415 nm was found to be principal source where GQD are interacting. By varying the GQD amount to low, medium, and high concentration, the effect of H 2 O 2 acted consequently, altering the PL emission during experiment in aqueous phase. An oxygen rich environment (ORE) occurred due to H 2 O 2 which oxides the ZnO surface. Low GQD concentration resulted affected by an ORE weakening the GQD-ZnO contact, decreasing PL emission. In high GQD concentration, H 2 O 2 induced GQD to reach the ZnO surface, increasing the PL emission. Only medium GQD concentration prevented oxidation of ZnO and maintained the PL emission intensity constant. When H 2 O 2 concentration increased, for the medium GQD concentration, an excess of charge by peroxides inhibited the charge transfer from GQD to ZnO. This inhibition produces a quenching of the PL emission., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)

Multifunctional materials based on carbon xerogel (CX) with embedded bismuth (Bi) and iron (Fe) nanoparticles are tested for ultrasensitive amperometric detection of lead cation (Pb 2+ ) and hydrogen peroxide (H 2 O 2 ). The prepared CXBiFe-T nanocomposites were annealed at different pyrolysis temperatures (T, between 600 and 1050 °C) and characterized by X-ray diffraction (XRD), Raman spectroscopy, N 2 adsorption, dynamic light scattering (DLS), and electron microscopies (SEM/EDX and TEM). Electrochemical impedance spectroscopy (EIS) and square wave anodic stripping voltammetry (SWV) performed at glassy carbon (GC) electrodes modified with chitosan (Chi)-CXBiFe-T evidenced that GC/Chi-CXBiFe-1050 electrodes exhibit excellent analytical behavior for Pb 2+ and H 2 O 2 amperometric detection: high sensitivity for Pb 2+ (9.2·10 5 µA/µM) and outstanding limits of detection (97 fM, signal-to-noise ratio 3) for Pb 2+ , and remarkable for H 2 O 2 (2.51 µM). The notable improvements were found to be favored by the increase in pyrolysis temperature. Multi-scale parameters such as (i) graphitization, densification of carbon support, and oxide nanoparticle reduction and purification were considered key aspects in the correlation between material properties and electrochemical response, followed by other effects such as (ii) average nanoparticle and Voronoi domain dimensions and (iii) average CXBiFe-T aggregate dimension.

In recent years, the development of nanomaterials-based peroxidase mimics as enzyme sensors has been attracting considerable interest due to their outstanding features, including potent stability, and cost-effectiveness toward natural enzymes. In this work, mesoporous silica nanoparticles functionalized by copper (Cu-MSN) were prepared as a new artificial enzyme for the first time through the sol-gel procedure. A comprehensive investigation of the catalytic activity of Cu-MSN was done through the oxidation of chromogenic peroxidase substrates, 3,3',5,5'-tetramethylbenzidine (TMB), and (2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), in the presence of H 2 O 2 . The results indicate that the peroxidase-like activity of the as-prepared sample is significantly higher than other nanoparticles. Additionally, for the study, a facile and rapid sensing method based on the enzyme-like activity of Cu-MSN to detect H 2 O 2 and glutathione (GSH) was developed to examine the potency of the proposed biosensor. Preliminary analysis revealed that the limit of detection (LOD) of H 2 O 2 and GSH is 0.2 and 0.0126 μM, in the range of 0.9-100 and 0.042-1 μM, respectively. These findings support the claims for the efficiency of the sensor in detection fields. Also, human serum was utilized as the real sample to obtain additional evidence., (© 2023. The Author(s), under exclusive licence to The Japan Society for Analytical Chemistry.)

Vertically stacked artificial 2D superlattice hybrids fabricated through molecular-level hybridization in a controlled fashion play a vital role in scientific and technological fields, but developing an alternate assembly of 2D atomic layers with strong electrostatic interactions could be much more challenging. In this study, we have constructed an alternately stacked self-assembled superlattice composite through integration of CuMgAl layered double hydroxide (LDH) nanosheets having positive charge with negatively charged Ti 3 C 2 T x layers using well-controlled liquid-phase co-feeding protocol and electrostatic attraction and investigated its electrochemical performance in sensing early cancer biomarkers, i.e ., hydrogen peroxide (H 2 O 2 ). The molecular-level CuMgAl LDH/Ti 3 C 2 T x superlattice self-assembly possesses superb conductivity and electrocatalytic properties, which are significant for obtaining a high electrochemical sensing aptitude. Electron penetration in Ti 3 C 2 T x layers and rapid ion diffusion along 2D galleries have shortened the diffusion path and enhanced the charge transferring efficacy. The electrode modified with the CuMgAl LDH/Ti 3 C 2 T x superlattice has demonstrated admirable electrocatalytic abilities in H 2 O 2 detection with a wide linear concentration range and low real-time limit of detection (LOD) of 0.1 nM with signal/noise ratio (S/N) = 3. Practically, an electrochemical sensing podium based on the CuMgAl LDH/Ti 3 C 2 T x superlattice has been effectively applied in real-time in vitro tracking of H 2 O 2 effluxes excreted from different live cancer cells and normal cells after being encouraged by stimulation. The results exhibit that molecular-level heteroassembly holds great potential in electrochemical sensors to detect promising biomarkers.

The lack of systematic structural resolution makes it difficult to build specific transition-metal-atom-doped carbonized polymer dots (TMA-doped CPDs). Herein, the structure-activity relationship between Cu atoms and CPDs was evaluated by studying the peroxidase-like properties of Glu-Cu-CPDs prepared by using copper glutamate (Glu) with a Cu-N 2 O 2 initial structure. The results showed that the Cu atoms bound to Glu-Cu-CPDs in the form of Cu-N 2 C 2 , indicating that Cu-O bonds changed into Cu-C bonds under hydrothermal conditions. This phenomenon was also observed in other copper-doped CPDs. Moreover, the carboxyl and amino groups content decreased after copper-atom doping. Theoretical calculations revealed a dual-site catalytic mechanism for catalyzing H 2 O 2 . The detection of intracellular H 2 O 2 suggested their application prospects. Our study provides an in-depth understanding of the formation and catalytic mechanism of TMA-doped-CPDs, allowing for the generation specific TMA-doped-CPDs., (© 2022 Wiley-VCH GmbH.)

Peroxidase enzymes enable the construction of electrochemical sensors for highly sensitive and selective quantitative detection of various molecules, pathogens and diseases. Herein, we describe the immobilization of a peroxidase from Bacillus s. (BsDyP) on electrochemically reduced graphene oxide (ERGO) deposited on indium tin oxide (ITO) and polyethylene terephthalate (PET) layers. XRD, SEM, AFM, FT-IR and Raman characterization of the sensor confirmed its structural integrity and a higher enzyme surface occupancy. The BsDyP-ERGO/ITO/PET electrode performed better than other horseradish peroxidase-based electrodes, as evinced by an improved electrochemical response in the nanomolar range (linearity 0.05-280 μM of H 2 O 2 , LOD 32 nM). The bioelectrode was mechanically robust, active in the 3.5-6 pH range and exhibited no loss of activity upon storage for 8 weeks at 4 °C., (© 2022 The Authors. ChemBioChem published by Wiley-VCH GmbH.)

Single-chain polymer nanoparticles (SCNPs) are soft matter constructed by intrachain crosslinks, with promising prospects in detection and catalysis. Herein, a fluorescent core (SCNPs) with aggregation-induced emission (AIE) is prepared, applying for H 2 O 2 detection through intermolecular heavy-atom effect. In detail, the SCNPs precursors are synthesized by ring-opening copolymerization. Then the SCNPs are prepared by intramolecularly cross-linking via olefin metathesis. Imitating the structure of AIE dots, SCNPs are encapsulated by H 2 O 2 -responsive polymers. Probably due to the stable secondary structure of SCNPs, the obtained micelles show stable fluorescence performance. Furthermore, as the heavy-atom, tellurium is introduced into the carriers to construct the heavy-atom effect. In this micelle-based system, the SCNPs act as the fluorescent core, and the stimuli-responsive polymer acts as the carrier and the fluorescent switch. The hydrophilicity of the tellurium-containing segment is affected by the concentration of H 2 O 2 , resulting in a change in the distance from the SCNPs, which ultimately leads to a change in the fluorescence intensity. Furthermore, tellurium is particularly sensitive to H 2 O 2 , which can detect low concentrations of H 2 O 2 . The SCNPs are merged with AIE materials, with the hope of exploring new probe designs., (© 2022 Wiley-VCH GmbH.)

We aimed to synthesize sensitive electrochemical sensors for hydrogen peroxide sensing by using zinc oxide nanorods grown on a fluorine-doped tin oxide electrode by using the facial hydrothermal method. It was essential to keep the surface morphology of the material (nanorods structure); due to its large surface area, the concerned material has enhanced detection ability toward the analyte. The work presents a non-enzymatic H 2 O 2 sensor using vertically grown zinc oxide nanorods on the electrode (FTO) surfaces with Cu nanoparticles deposited on zinc oxide nanorods to enhance the activity. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-Ray (EDX), X-ray diffraction (XRD), and electrochemical methods were used to characterize copper-zinc oxide nanorods. In addition to the high surface area, the hexagonal Cu-ZnO nanorods exhibited enhanced electrochemical features of H 2 O 2 oxidation. Nanorods made from Cu-ZnO exhibit highly efficient sensitivity of 3415 μAmM -1 cm -2 low detection limits (LODs) of 0.16 μM and extremely wide linear ranges (0.001-11 mM). In addition, copper-zinc oxide nanorods demonstrated decent reproducibility, repeatability, stability, and selectivity after being used for H 2 O 2 sensing in water samples with an RSD value of 3.83%. Cu nanoparticles decorated on ZnO nanorods demonstrate excellent potential for the detection of hydrogen peroxide, providing a new way to prepare hydrogen peroxide detecting devices., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer DK declared a past co-authorship with the author IK to the handling editor., (Copyright © 2022 Arsalan, Saddique, Baoji, Awais, Khan, Shamseldin and Mehrez.)

Herein, an Au nanoparticles-polydopamine-poly acrylic acid-graphene (Au NPs-PDA-PAA-graphene) multicomponent nanohybrid is fabricated by surface functionalization of graphene alongside extensive in-situ growth of Au nanoparticles. The as-obtained nanocomposite possesses good hydrophilicity, excellent biocompatibility and high biomolecules loading capacity, which acts as an ideal platform for enzyme modification. Considering this fact, Horseradish peroxidase is expressively immobilized upon Au NPs-PDA-PAA-graphene surface, in order to lay the foundations of a biosensor that is majorly based on enzymatic activity. The biosensor exhibits higher sensitivity towards the determination of H 2 O 2 with linearity ranging from 0.1 μm upto 20 mm, and the limit of detection going down to 0.02 μm. Encouraged by its acceptable electrocatalytic performance, this multicomponent system can also be easily employed for carrying out the real-time tracking of H 2 O 2 coming out of Macrophage cells. Therefore, this work designs an extraordinarily updated platform for biosensing related applications, and also presents a reliable platform for the direct detection of H 2 O 2 in vivo and in vitro , which show great potential in bioelectroanalytical chemistry, cellular biology, and pathophysiology., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Tong, Asif, Ajmal, Aziz and Sun.)

It has been demonstrated that defect engineering is an effective strategy to enhance the activity of materials. Herein, a polycrystalline GaN porous layer (PGP) with high catalytic activity was grown by self-assembly on GaN-coated sapphire substrate by using low-temperature (LT) MOCVD growth. Without doping, LT growth can significantly improve the activity and electrical conductivity of PGP, owing to the presence of rich N-vacancies (∼10 20 cm -3 ). Identification of rich N-vacancies in the PGP material was realized by using atomically resolved STEM (AR-STEM) characterization. The optimized PGP was applied to catalyst-free electrochemical detection of H 2 O 2 with a limit of detection (LOD) of 50 nM, a fast response speed of 3 s, a wide linear detection range (50 nM to 12 mM), and a high stability. The LOD is exceeding 40 fold lower than that of reported metal-catalyst decorated GaN. Moreover, a quantitative relationship between the sensing performances and N-vacancy of PGP was established. To our knowledge, it is the first time that intrinsic GaN materials can exhibit high catalytic activity.

A super-porous hybrid platform can offer significantly increased number of reaction sites for the analytes and thus can offer advantages in the biosensor applications. In this work, a significantly improved sensitivity and selectivity of hydrogen peroxide (H 2 O 2 ) detection is demonstrated by a super-porous hybrid CuO/Pt nanoparticle (NP) platform on Si substrate as the first demonstration. The super-porous hybrid platform is fabricated by a physiochemical approach combining the physical vapor deposition of Pt NPs and electrochemical deposition of super-porous CuO structures by adopting a dynamic hydrogen bubble technique. Under an optimized condition, the hybrid CuO/Pt biosensor demonstrates a very high sensitivity of 2205 µA/mM·cm 2 and a low limit of detection (LOD) of 140 nM with a wide detection range of H 2 O 2 . This is meaningfully improved performance as compared to the previously reported CuO-based H 2 O 2 sensors as well as to the other metal oxide-based H 2 O 2 sensors. The hybrid CuO/Pt platform exhibits an excellent selectivity against other interfering molecules such as glucose, fructose, dopamine, sodium chloride and ascorbic acid. Due to the synergetic effect of highly porous CuO structures and underlying Pt NPs, the CuO/Pt architecture offers extremely abundant active sites for the H 2 O 2 reduction and electron transfer pathways.

The successful synthesis is reported of Mn, Fe, Co, Ni, Cu-doped g-C 3 N 4 nanoflakes via a simple one-step pyrolysis method, respectively. Among them, the Fe-doped g-C 3 N 4 nanoflakes exhibited the highest peroxidase-like activity, which can be used for colorimetric detection of hydrogen peroxide (H 2 O 2 ) and sarcosine (SA), within the detection ranges of 2-100 μM and 10-500 μM and detection limits of 1.8 μM and 8.6 μM, respectively. The catalytic mechanism of the Fe-doped g-C 3 N 4 nanoflake was also explored and verified the generation of hydroxyl radical (•OH) through fluorescence method. It is believed that the Fe-doped g-C 3 N 4 nanoflakes as enzyme mimics will greatly promote the practical applications in a variety of fields in the future including biomedical science, environmental governance, antibacterial agent, and bioimaging due to their extraordinary catalytic performance and stability. Graphical abstract.

In situ monitoring of hydrogen peroxide (H 2 O 2 ) during its production process is needed. Here, an electrochemical H 2 O 2 sensor with a wide linear current response range (concentration: 5 × 10 -8 to 5 × 10 -2 m), a low detection limit (32.4 × 10 -9 m), and a high sensitivity (568.47 µA mm -1 cm -2 ) is developed. The electrocatalyst of the sensor consists of cobalt nanoparticles and atomic Co-N x moieties anchored on nitrogen doped carbon nanotube arrays (Co-N/CNT), which is obtained through the pyrolysis of the sandwich-like urea@ZIF-67 complex. More cobalt nanoparticles and atomic Co-N x as active sites are exposed during pyrolysis, contributing to higher electrocatalytic activity. Moreover, a portable screen-printed electrode sensor is constructed and demonstrated for rapidly detecting (cost ≈40 s) H 2 O 2 produced in microbial fuel cells with only 50 µL solution. Both the synthesis strategy and sensor design can be applied to other energy and environmental fields., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

For the first time, the synthesis, characterization, and analytical application for hydrogen peroxide quantification of the hybrid materials of Co 2 TiO 4 (CTO) and reduced graphene oxide (RGO) is reported, using in situ (CTO/RGO) and ex situ (CTO+RGO) preparations. This synthesis for obtaining nanostructured CTO is based on a one-step hydrothermal synthesis, with new precursors and low temperatures. The morphology, structure, and composition of the synthesized materials were examined using scanning electron microscopy, X-ray diffraction (XRD), neutron powder diffraction (NPD), and X-ray photoelectron spectroscopy (XPS). Rietveld refinements using neutron diffraction data were conducted to determine the cation distributions in CTO. Hybrid materials were also characterized by Brunauer-Emmett-Teller adsorption isotherms, Scanning Electron microscopy, and scanning electrochemical microscopy. From an analytical point of view, we evaluated the electrochemical reduction of hydrogen peroxide on glassy carbon electrodes modified with hybrid materials. The analytical detection of hydrogen peroxide using CTO/RGO showed 11 and 5 times greater sensitivity in the detection of hydrogen peroxide compared with that of pristine CTO and RGO, respectively, and a two-fold increase compared with that of the RGO+CTO modified electrode. These results demonstrate that there is a synergistic effect between CTO and RGO that is more significant when the hybrid is synthetized through in situ methodology.

Precise designs of low-cost and efficient catalysts for the detection of hydrogen peroxide (H 2 O 2 ) over wide ranges of pH are important in various environmental applications. Herein, a versatile and ecofriendly approach is presented for the rational design of ternary bentonite-silylpropyl-polypyrrole/silver nanoarchitectures (denoted as BP-PS-PPy/Ag) via the in-situ photo polymerization of pyrrole with salinized bentonite (BP-PS) in the presence of silver nitrate. The Pyrrolyl-functionalized silane (PS) is used as a coupling agent for tailoring the formation of highly exfoliated BP-PS-PPy sheet-like nanostructures ornamented with monodispersed Ag nanoparticles (NPs). Taking advantage of the combination between the unique physicochemical properties of BP-PS-PPy and the outstanding catalytic merits of Ag nanoparticles (NPs), the as-synthesized BP-PS-PPy/Ag shows a superior electrocatalytic reduction and high-detection activity towards H 2 O 2 under different pH conditions (from 3 to 10). Intriguingly, the UV-light irradiation significantly enhances the electroreduction activity of H 2 O 2 substantially, compared with the dark conditions, due to the high photoelectric response properties of Ag NPs. Moreover, BP-PS-PPy/Ag achived a quick current response with a detection limit at 1 μM within only 1 s. Our present approach is green, facile, scalable and renewable.

3D printing technologies have been considered an important technology due to the ease manufacturing of objects, freedom of design, waste minimization, and fast prototyping. In chemistry, this technology potentializes the fabrication of conductive electrodes in large scale for sensing applications. Herein, we reported the modification of a 3D printed graphene electrode with Prussian blue. The modified electrode (3DGrE/PB) was characterized by microscopy (SEM and AFM) and spectroscopic techniques, and its electrochemical properties were compared to the traditional electrodes: glassy carbon, gold, and platinum. The 3DGrE/PB was used in the sensing of hydrogen peroxide in real-world samples of milk and mouthwash, and the results obtained according to the technique of batch-injection analysis were satisfactory for the concentration range typically found in such samples. Thus, 3DGrE/PB can be used as a new platform for sensing of molecular targets.

The mechanism behind the variation in the photoluminescence (PL) of a MoS 2 nanohybrid material with pH was investigated. Highly fluorescent MoS 2 quantum dots dispersed across MoS 2 nanosheets (MoS 2 QDNS) were synthesized by a hydrothermal route in the presence of NaOH. Upon reducing the pH from 13 to 6.5, the PL intensity was markedly quenched. The removal of dangling sulfur atoms by adding mineral acids could be a plausible mechanism for this PL quenching, together with the inner filter effect and Förster resonance energy transfer due to the resulting species. A label-free turn-on fluorescence sensor for H 2 O 2 was developed using this hybrid material. The PL of the acidified MoS 2 QDNS at pH 6.5 increased (i.e., recovered) linearly with the concentration of H 2 O 2 . The dynamic range of the sensor was found to be 2-94 μM with a limit of detection (LOD) of 2 μM. This sensing strategy was also extended for the detection of glucose by appending glucose oxidase (GOx) as a catalyst. In the presence of GOx, glucose oxidizes to gluconic acid and H 2 O 2 , so the original level of glucose can be estimated by determining the H 2 O 2 present. The absence of a complicated enzyme immobilization step is the prime advantage of the present glucose sensor. The current work exemplifies the utility of MoS 2 -based nanoparticle systems in the biological sensor domain. Graphical abstract.

Lignin is the second largest naturally renewable resource and is primarily a by-product of the pulp and paper industry; however, its inefficient use presents a challenge. In this work, Fe₃O₄ nanoparticles loaded on lignin nanoparticles (Fe₃O₄@LNPs) were prepared by the self-assembly method and it possessed an enhanced peroxidase-like activity. Fe₃O₄@LNPs catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂ to generate a blue color, was observable by the naked eye. Under the optimal conditions, Fe₃O₄@LNPs showed the ability of sensitive colorimetric detection of H₂O₂within a range of 5⁻100 μM and the limit of detection was 2 μM. The high catalytic activity of Fe₃O₄@LNPs allows its prospective use in a wide variety of applications, including clinical diagnosis, food safety, and environmental monitoring.

Various 3-dimensional C/CeO 2 hollow nanostructure frameworks (3D C/CeO 2 HNFs) were synthesized by using a polymer blowing process that is accelerated by adding a certain amount of cerium nitrate. Polyvinylpyrrolidone was used as the polymer. The resulting HNFs were characterized by scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy. The HNFs possess a large specific surface area, and the CeO 2 nanocrystals consist of a single phase. The HNFs display intrinsic peroxidase-like activity and can catalyze the oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine in the presence of H 2 O 2 to produce a blue product. The method was applied to the quantification of H 2 O 2 with a 5.2 nM detection limit. The analytical range is from 10 nM to 1 μM. Graphical abstract Schematic of the preparation of a 3-dimensional C/CeO 2 hollow nanostructure framework by a polyvinylpyrrolidone-blowing process accelerated by Ce(NO 3 ) 3 . They were applied to H 2 O 2 detection by catalyzing the oxidation of peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) to the oxidized 3,3',5,5'-tetramethylbenzidine (oxTMB) to produce blue-color reaction.

Artificial enzymes is an emerging field of research owing to the remarkable advantages of enzyme mimics over their natural counterpart, including tunable catalytic efficiencies, lower cost, ease of preparation, and excellent tolerance to variations of the reaction system. Herein, we report an efficient peroxidase mimic based on a copper-modified covalent triazine framework (CCTF). Owing to its unique specific surface area, atomically dispersed active Cu sites, efficient electron transfer, and enhanced photo-assisted enzyme-like activity, the CCTF showed enhanced peroxidase-like enzyme activity. Therefore, copper modification represents an effective route to tailor the peroxidase-like activity of the covalent triazine frameworks. Furthermore, the mechanism of the enhanced peroxidase-like activity and stability of the CCTF were investigated. As a proof of concept, the CCTF was used for the colorimetric detection of H 2 O 2 and decomposition of organic pollutants. This work provides a new strategy for the design of enzyme mimics with a broad range of potential applications., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Rare earth (RE) phosphates and vanadates are structurally similar compositions that display distinct but complementary luminescent properties. The properties of these phosphors can be combined in REPO 4 -REVO 4 heterostructures during the development of new sensing technologies for biological applications. This work presents the synthesis of hollow RE phosphate/vanadate colloidal particles and evaluates their applicability as luminescent markers. Hydrothermal treatments of RE hydroxycarbonate particles in the presence of the PO 4 3- and VO 4 3- precursors afforded the final REPO 4 -REVO 4 solids in a two-step template synthesis. We converted precursor hydroxycarbonate particles into the final heterostructures and characterized their structure and morphology. According to our detailed study into the spectroscopic properties of Eu 3+ -doped particles and their luminescence response to several species, the presence of the phosphate and vanadate phases in a single particle provided different chemical environments and enabled the design of a ratiometric approach to detect H 2 O 2 . These results open new perspectives for the development of new intracellular luminescent markers.

A green version of the "Fe" impurity-induced peroxidase mimicry exhibited by simple and cheap substrate "nanoclay (NC)" along with the highly sensitive amperometric and spectrophotometric determination of cholesterol is demonstrated. The "Fe" impurity can act as the catalyst center for hydrogen peroxide reduction similar to the horseradish peroxidase (HRP)-catalyzed reaction. The Michaelis-Menten constant for the NC-catalyzed reaction is found to be lower than that of the HRP-catalyzed reaction indicating high affinity for the substrate. The NC-modulated peroxidase-like catalytic activity originates from the electron transfer between the reducing substrate in the catalyst center and H2O2 with the intermediate generation of hydroxyl radicals. The peroxidase mimicry is successfully applied for the low-potential electrochemical detection of H2O2 (linear detection range 1.96-10.71 mM, R (2) = 0.97). The H2O2 sensing platform is further modified with cholesterol oxidase (CHOx) for the spectrophotometric (linear detection range 50-244 μM, R (2) = 0.99) and amperometric detection of cholesterol (linear detection range 0.099-1.73 mM, R (2) = 0.998). Graphical abstract Peroxidase mimicry of nanoclay for the determination of cholesterol.

Acylated xylan-based magnetic Fe₃O₄ nanocomposite hydrogels (ACX-MNP-gels) were prepared by fabricating Fe₃O₄ nanoctahedra in situ within a hydrogel matrix which was synthesized by the copolymerization of acylated xylan (ACX) with acrylamide and N -isopropylacrylamide under ultraviolet irradiation. The size of the Fe₃O₄ fabricated within the hydrogel matrix could be adjusted through controlling the crosslinking concentrations (C). The magnetic hydrogels showed desirable magnetic and mechanical properties, which were confirmed by XRD, Raman spectroscopy, physical property measurement system, SEM, TGA, and compression test. Moreover, the catalytic performance of the magnetic hydrogels was explored. The magnetic hydrogels (C = 7.5 wt %) presented excellent catalytic activity and provided a sensitive response to H₂O₂ detection even at a concentration level of 5 × 10 -6 mol·L -1 . This approach to preparing magnetic hydrogels loaded with Fe₃O₄ nanoparticles endows xylan-based hydrogels with new promising applications in biotechnology and environmental chemistry.

Controlling the shape, structure, and surface morphology of nanomaterials is of great significance in optimizing sensitivity and catalytic performances in biosensing applications. The main goal of employing Pt-based nanomaterials is to increase their utilization efficiency due to their high cost. Herein, we report the synthesis of mesoporous Pt nanotubes using Pluronic P123 as soft templates and Ag nanowires with 50 nm in diameter as hard templates. The resultant materials with unique structures show high sensitivity and stability toward H2O2 detection with low cellular cytotoxicity. The high sensitivity and catalytic properties are attributed to the mesopores and hollow structures making the inner Pt surfaces accessible to reaction media and enlarging the total surface area and one-dimensional structure facilitating the mass diffusion rate.