Urease is closely associated with microorganisms, plants, and animals, playing a vital role in biomedical and agricultural fields. In this study, gold nanoclusters (Au NCs) were impregnated onto the surface of ZIF-8 to form Au-ZIF nanocomposite, which induces a confinement effect on the configuration and electrons of Au NCs, leading to a more than ten-fold enhancement in the fluorescence intensity of Au NCs at 583nm. The Au-ZIF nanocomposite exhibits excellent pH-sensitive fluorescence properties owing to the acid-induced decomposition of ZIF-8. By utilizing fluorescent silicon quantum dots (Si QDs) as a blue-emissive internal reference, the Au-ZIF/Si QDs system enables sensitive fluorescence sensing of both pH and urease. The established sensing system achieved a detection range of pH 5.5-7.5, and 5–140 U/L for urease, with a detection limit as low as 1.85 U/L. Furthermore, a portable hydrogel sensing platform was developed for the visual monitoring of pH and urease under ultraviolet light. This visual hydrogel sensing platform achieved satisfactory recoveries for urease detection in lake water and biological samples.

Herein, a novel Ti3C2Tx MXene-based nanozyme (CoN-TiC) with remarkable peroxide-like activity was successfully synthesized. CoN-TiC can catalyze hydrogen peroxide (H2O2) to produce reactive oxygen species (ROS), which could oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) into oxTMB with characteristic absorption peak at 650 nm. Cu doped silicon quantum dots (Cu-SiQDs) with excellent fluorescence property was used as the fluorescence probes. The fluorescence of Cu-SiQDs at 458 nm would be quenched by oxTMB due to inner filter effect. Gallic acid (GA) as a typical antioxidant had great free radical scavenging ability, it could inhibit the oxidization of TMB into oxTMB, so the fluorescence of Cu-SiQDs would be restored. Therefore, a colorimetric and fluorometric sensing platform that had dual output signals and self-correction function was strategically constructed for GA determination. This sensing system possessed excellent sensitivity with low limits of detection (LOD) of 0.12 μM (fluorescent method) and 0.20 μM (colorimetric method). Moreover, this proposed platform was successfully applied to detect GA in green tea samples.

Interfacial energy level mismatch and inefficient charge extraction at bioelectrochemical interfaces have remained major bottlenecks for enzymatic biofuel cell-based self-powered sensing systems. Here, we reported a built-in electric field (BIEF) enabled self-powered sensing platform for intelligent dual-mode detection of 17 beta-estradiol (E2), featuring an energy level engineered Janus bioanode that uses work function differences to drive directional charge extraction during cascade biocatalysis. The Janus heterointerface was constructed by Zn-O-Ti coordination between unsaturated Zn2+ sites in ZIF-8-NH2 and -O-terminated Ti3C2T x , inducing an intrinsic BIEF and strengthened interfacial electronic coupling. Density functional theory calculations revealed favorable energy level alignment between the enzymatic redox donor FADH2 (-4.73 eV) and the Zn-O-Ti interface (-5.11 eV), enabling low barrier electron injection and enhanced bioelectrocatalysis. For E2 sensing, an aptamer triggered hybridization chain reaction regulated methylene blue loading on the biocathode, converting target recognition into coupled electrochemical and optical outputs. The enzymatic biofuel cell was integrated on a screen-printed electrode with an IoT connected voltmeter for real-time wireless readout, while machine learning-assisted fusion improved analytical robustness in piped water, lake water, and human serum. This work highlighted Janus interfacial energy level engineering as a general strategy for regulating charge transfer in bioelectrochemical systems.

The application of metal halide perovskite (CsPbX3) nanocrystals (NCs) is often hampered by the poor stability. Herein, CsPbX3 NCs were encapsulated in dendritic mesoporous silica nanoparticles (DMSNs) to enhance stability and suppress surface defects, and consequently improved the PL (Photoluminescence) quantum yield. Through modulating the halide molar ratio, tunable multicolor emission across the entire visible spectrum of 414-682 nm was achieved. A colorimetric and fluorescence dual-signal sensing system was developed by combining Co-Fe layered double hydroxide (CoFeLDH) with red-emissive CsPb(Br/I)3@DMSNs for detection of fluoroquinolone antibiotics. 3,3',5,5'-tetramethylbenzidine (TMB) could be catalyzed by CoFeLDH to generate blue oxTMB. Furthermore, the TMB oxidation process was significantly accelerated by the addition of fluoroquinolones antibiotics. The produced oxTMB could quench the fluorescence of CsPb(Br/I)3@DMSNs, enabling dual-mode detection of enrofloxacin (ENR) through colorimetric enhancement and fluorometric suppression, which was high sensitive for the ENR with limit of detection of 4.23 nM and 2.55 nM, respectively. Besides, this sensing strategy could be extended to the detection of other fluoroquinolones antibiotics including ciprofloxacin (CIP) and norfloxacin (NOR).

The growing imperative to ensure food safety, preserve ecological integrity, and mitigate public health risks associated with pesticide residues has driven a critical demand for highly sensitive optical sensors. In this regard, optical biosensors, including fluorescence (FL), colorimetry (CL), surface-enhanced Raman scattering (SERS), surface plasmon resonance (SPR), and chemiluminescence strategies, have been developed for pesticide detection. This review aims to provide a comprehensive summary of both fundamental knowledge and advancements in the field of optical biosensors for pesticide detection. The advantages of these biosensors are highlighted, such as excellent sensitivity, high specificity, and on-site application. Subsequently, a detailed overview of the sensing mechanism of optical biosensors based on different molecular recognition elements [e.g., enzymes, antibodies, aptamers, molecularly imprinted polymers (MIPs), and supramolecular host–guest complexes] is provided. Finally, perspectives are offered on the current challenges and future directions of pesticide biosensors. This review is expected to serve as a fundamental guide for researchers in the field of optical biosensors for pesticide detection and to provide insights and avenues to enhance the performance of existing sensing mechanisms in applications across diverse fields.

Tert-butylhydroquinone (TBHQ) as a cost-effective synthetic and efficient antioxidant is extensively added to food products, excessive intake of TBHQ is associated with potential health risks. Herein, a colorimetric and fluorometric detection method integrating FeSnO(OH)5/Pt nanoparticles (Pt NPs) and CsPbBr3@DMSNs for the sensitive detection of TBHQ was developed. CsPbBr3@DMSNs nanocomposites were prepared by embedding CsPbBr3 nanocrystals (NCs) within dendritic mesoporous silica nanoparticles (DMSNs), resulting in excellent aqueous stability and enhanced luminescence properties. Pt NPs were in situ grown on FeSnO(OH)5 nanocubes with a favorable specific surface area by a coprecipitation method, yielding the FeSnO(OH)5/Pt NPs with excellent peroxidase-like activity. 3,3',5,5'-tetramethylbenzidine (TMB) could be catalyzed by FeSnO(OH)5/Pt NPs to produce oxTMB, thereby quenching the fluorescence of CsPbBr3@DMSNs by inner filter effect. TBHQ has potent antioxidant properties and could prevent TMB from being oxidized, thereby recovering the fluorescence of CsPbBr3@DMSNs. Hence, a colorimetric and fluorescence dual-signal detection system for TBHQ detection was developed, with LODs of 3.52 µM and 2.12 µM, respectively. Moreover, this sensing platform was successfully used for the TBHQ determination in edible oils, indicating good practicability.

Quercetin, a potent natural antioxidant, is gaining widespread attention for its remarkable health benefits, including the prevention of cardiovascular diseases, allergies, diabetes, and cancer. As a promising functional food ingredient, there is an urgent need for fast, sensitive, and portable methods to monitor quercetin levels in various products. In this study, we present a portable dual-mode nanozyme-driven sensor based on cerium dioxide nanoparticle-anchored metal-organic framework (CeO2@UiO-66-NH2) nanocomposite. This nanocomposite exhibits impressive oxidase-like activity and intrinsic fluorescence properties, enabling it to catalyze the oxidation of colorless N, N-diethyl-p-phenylenediamine to a pink product, which in turn quenches the fluorescence of CeO2@UiO-66-NH2 at 458 nm via an inner filter effect (IFE). The presence of quercetin inhibits reactive oxygen species generation, thus attenuating the oxidation and restoring fluorescence. A paper-based fluorescent-colorimetric dual-mode sensing platform was established for quercetin detection, enabling rapid and visual evaluation without complex instruments. The proposed method exhibited a broad linear response range of 1-60 μM. The limits of detection for the colorimetric/fluorescent and paper-based colorimetric/fluorescent were 0.35, 0.27, 0.37, and 0.29 μM, respectively. This dual-mode sensor demonstrates excellent analytical sensitivity and selectivity, with successful application in real vegetable and juice samples, offering a reliable, efficient tool for quercetin monitoring in food and functional food ingredients.

This study constructs a wearable microneedle sensing platform integrated with a bicatalytic nanozyme, enabling minimally invasive detection of dopamine (DA) in interstitial fluid. Firstly, a dual-enzyme mimic nanozyme (CMCO-S) with high catechol oxidase and catalase activities was synthesized via the Mn and S co-doping strategy. It was then employed to construct a highly efficient self-oxygenating cyclic cascade sensing system. Specifically, catechol oxidase activity catalyzes the oxidation of catechol compounds in the presence of O2, simultaneously generating H2O2 as an intermediate product. Subsequently, catalase activity immediately decomposes the generated H2O2 into O2 and H2O, thereby achieving self-sustaining oxygen recycling and efficient reuse. This closed-loop cascade reaction significantly enhances the catalytic efficiency and realizes effective signal amplification. Based on this cyclic system, the present study further developed a rapid and ultrasensitive dual-mode method for dopamine detection. In the presence of resorcinol, both the 478 nm fluorescence and 420 nm absorbance of the catalytic products display remarkable positive linear correlations with dopamine concentration. The two modes cover linear ranges of 0.03-100 μM and 0.1-100 μM, with limits of detection (LOD) of 0.016 μM and 0.049 μM, and the assay is completed within 5 min. By integrating this self-sustaining oxygen-driven cascade amplification sensing system into a gel microneedle patch, a visualized analysis platform capable of both extracting and detecting dopamine in skin interstitial fluid was ultimately constructed. This work provides a practically feasible strategy for developing wearable devices for dopamine detection in interstitial fluid.

Catecholamine neurotransmitters and their metabolites are important biomarkers associated with neurodegenerative diseases, yet their accurate discrimination and quantification remain challenging due to structural similarity and complex biological environments. Herein, we report a tri-modal sensing platform based on metal-organic framework (MOF)-derived Co3O4 hollow nanocubes with in situ grown NiMn layered double hydroxide (Co3O4@NiMn-LDH) for the discrimination and quantification of catecholamine-related biomarkers. The oxidase-like performance of Co3O4@NiMn-LDH was significantly enhanced (1.98 U mg-1) through rationally regulation of the thickness of the NiMn-LDH shell. Using o-phenylenediamine (oPD) as the signal-responsive substrate and F-doped SiQDs as a blue-emissive fluorescent probe, the platform enabled colorimetric and ratiometric fluorescence sensing. Owing to their different reducing abilities, catecholamines and their metabolites inhibited oPD oxidation to varying extents, suppressing 2,3-diaminophenazine (DAP) formation and generating distinct absorbance signals. The decreased DAP production reduced fluorescence at 565 nm, while the emission of F-doped SiQDs at 469 nm was restored, yielding a reliable ratiometric fluorescence response. In the electrochemical channel, catecholamine-related compounds generated distinct current responses due to their different electrooxidation activities. Therefore, the tri-modal sensing platform was established for the quantification of epinephrine (EP), dopamine (DA), norepinephrine (NE), vanillylmandelic acid (VMA), and homovanillic acid (HVA) with satisfactory linear responses over a wide concentration range (1-100 μM). Moreover, machine learning-assisted linear discriminant analysis (LDA) enabled effective discrimination of these biomarkers. The tri-modal platform exhibited reliable performance in complex samples, indicating its potential for multimodal analysis of structurally similar neuroactive molecules and neurodegenerative disease diagnosis.

The sensitive and accurate monitoring of acetylcholinesterase (AChE) is of vital significance for neurological diseases. Current dual-mode sensing of AChE is mostly limited to the simple physical mixing of multiple materials, making it challenging to achieve multifunctional synergistic enhancement. In this work, a novel MOF-on-MOF nanozyme (AuNC@ZIF/MIL) was fabricated by coating zeolitic imidazolate framework-8 (ZIF-8) on the outer layer of metal-organic framework NH2-MIL-101(Fe) (ZIF/MIL) and immobilizing gold nanoclusters (AuNCs) on the shell layer. By virtue of the core-shell confinement effect and intercomponent synergy, the fluorescence emission efficiency of AuNCs and the peroxidase-like (POD) activity of the AuNC@ZIF/MIL composite were simultaneously enhanced. AChE is capable of catalyzing the hydrolysis of acetylcholine (ACh) into choline (ChO), which is further converted to hydrogen peroxide (H2O2) by choline oxidase (ChOx). Subsequently, in the presence of H2O2, AuNC@ZIF/MIL can facilitate the transformation of 3,3',5,5'-tetramethylbenzidine (TMB) into its oxidized state (oxTMB), thereby yielding an ultraviolet absorption signal. Meanwhile, the fluorescence emission of AuNC@ZIF/MIL at 445nm (derived from NH2-MIL-101(Fe)) and 581nm (derived from AuNCs) are quenched by in-situ generated H2O2. Thus, a fluorescence-colorimetric dual-signal AChE detection platform was fabricated by efficiently coupling AuNC@ZIF/MIL nanozyme and AChE/ChOx cascade reaction. This sensing platform was successfully applied for the detection of AChE activity in human whole blood.

Interfacial energy level mismatch and inefficient charge extraction at bioelectrochemical interfaces have remained major bottlenecks for enzymatic biofuel cell-based self-powered sensing systems. Here, we reported a built-in electric field (BIEF) enabled self-powered sensing platform for intelligent dual-mode detection of 17β-estradiol (E2), featuring an energy level engineered Janus bioanode that uses work function differences to drive directional charge extraction during cascade biocatalysis. The Janus heterointerface was constructed by Zn-O-Ti coordination between unsaturated Zn2+ sites in ZIF-8-NH2 and -O-terminated Ti3C2Tx, inducing an intrinsic BIEF and strengthened interfacial electronic coupling. Density functional theory calculations revealed favorable energy level alignment between the enzymatic redox donor FADH2 (-4.73 eV) and the Zn-O-Ti interface (-5.11 eV), enabling low barrier electron injection and enhanced bioelectrocatalysis. For E2 sensing, an aptamer triggered hybridization chain reaction regulated methylene blue loading on the biocathode, converting target recognition into coupled electrochemical and optical outputs. The enzymatic biofuel cell was integrated on a screen-printed electrode with an IoT connected voltmeter for real-time wireless readout, while machine learning-assisted fusion improved analytical robustness in piped water, lake water, and human serum. This work highlighted Janus interfacial energy level engineering as a general strategy for regulating charge transfer in bioelectrochemical systems.

Cysteine (Cys) was essential for cellular functions, its dysregulation strongly linked to neurodegenerative diseases, cardiovascular disorders, and liver dysfunction, emphasizing the necessity of early monitoring. MOFderived nanomaterials with nanozyme activity have garnered significant attention for their high surface area and versatile incorporation of functional groups. However, their poor electrical conductivity and low enzymelike activity limit their performance. In this work, through precise control of the Ni/Co ratio and perfect etching of the MIL framework, a well-defined hollow MIL structure with in-situ grown NiCo-LDH nanosheets (MIL-Ni1Co1LDH) was achieved to maximize catalytic site exposure and accelerate efficient electron charge transfer for superior sensing performance, achieving a high peroxidase activity of 3.7 U mg-1. The subsequent incorporation of gold nanoclusters (AuNCs) onto the MIL-derived LDH configuration (MIL-Ni1Co1LDH-AuNCs) enhances the conductivity and exceptional fluorescence properties. Furthermore, based on the successful material design and employing p-phenylenediamine (pPD) as a chromogenic substrate, a multimodal sensing platform was developed by integrating UV-vis absorbance, ratiometric fluorescence, and electrochemical analysis for highly sensitive and accurate Cys detection. Upon the introduction of Cys, a pronounced decrease in the UV-vis absorption peak was observed, accompanied by a remarkable recovery of ratiometric fluorescence intensity. Simultaneously, the electrochemical oxidation of Cys leads to a significant increase in current response. Noteworthy, this multimodal sensing approach enables accurate differentiation between Alzheimer's disease patients and healthy individuals by employing Cys as the biomarker, providing a valuable platform for neurodegenerative diseases diagnosis.

Three-dimensional carbon-based nanozymes derived from ZIFs generally suffer from severe morphology and skeleton collapse due to high-temperature pyrolysis and carbonization in the synthesis process, significantly reducing their catalytic activity. Moreover, their application is limited by a single catalytic activity. Herein, a novel Pt nanoparticles (Pt NPs) modified polydopamine (PDA) supported copper-nitrogen co-doped carbon-based nanozyme (P/Cu-NC@Pt) was synthesized with dual-enzyme mimicking activities. PDA was ingeniously introduced before the pyrolysis of Cu doped ZIF (CuZIF), supporting the material to maintain its three-dimensional structure, effectively avoiding structural collapse during the pyrolysis and increasing specific surface area and metal loading, which enhanced the catalytic activity. Furthermore, modifying Pt NPs evenly on the surface of P/Cu-NC through in-situ synthesis, ultimately obtained P/Cu-NC@Pt possessed excellent peroxidase-like activity and catalase-like activity at different pH value. Based on the peroxidase-like activity of P/Cu-NC@Pt and the fluorescence of Zn-doped AgNCs (Zn-AgNCs), a fluorescence and colorimetric detection platform for tannic acid (TA) was constructed with the limits of detection (LOD) of 0.039 and 0.17 μM. Based on the catalase-like activity of P/Cu-NC@Pt, a colorimetric detection platform for dopamine (DA) monitoring was achieved with the LOD of 1.76 μM. The constructed detection platforms obtained reliable detection results in actual samples with the average recoveries range of 93.06-104.90 %. Furthermore, combining the designed paper-based hydrogel sensor with the smartphone, the rapid visual analysis of TA and DA was successfully achieved. The proposed multi-mode flexible detection methods for TA and DA could simultaneously satisfy the on-site detection and laboratory detection.

Microcystin-LR (MC-LR), a potent hepatotoxin from cyanobacteria, poses serious environmental and public health risks, demanding sensitive and portable detection methods. We present an integrated self-powered system (ISPS) based on a vacancy-engineered porous Ti3C2Tx MXene-enabled enzymatic biofuel cell (PM-EBFC) for onsite MC-LR monitoring. Porous Ti3C2Tx (P-Ti3C2Tx) was synthesized via an environmentally friendly alkaline etching strategy, in which OH- adsorption promoted selective Ti removal, thereby lowering Ti vacancy formation energy and accelerating nanoscale pore evolution, as confirmed by DFT calculations. The resulting architecture exhibited high conductivity, abundant electroactive sites, and efficient interfacial electron transfer kinetics, enabling its use as the conductive matrix for both anodic and cathodic bioelectrodes. In the presence of MC-LR, RecJf exonuclease mediated cyclic amplification enhanced GOD loading at the bioanode, glucose oxidation released electrons that were transferred to the biocathode for oxygen reduction. This coupled enzymatic redox process generated a stable open-circuit voltage (EOCV) linearly correlated with MC-LR concentration. The ISPS, utilizing a screen-printed electrode and a Bluetooth-enabled data acquisition module, enabled realtime wireless EOCV recording on a smartphone. The system demonstrated high reproducibility, long-term stability, and reliable performance in tap water, lake water, and human serum, underscoring its potential for portable, self-powered environmental monitoring and clinical diagnostics.

Dopamine (DA) is a common neurotransmitter in living organisms, which is involved in a variety of physiological functions and behavioral responses, making the monitoring of its level crucial. Herein, a novel dual-signal sensing strategy based on a silver-based bifunctional nanozymes (Ag-HA) has been proposed for sensitive detection of DA concentration. The prepared Ag-HA exhibited both blue fluorescence and peroxidase-like activity. In the presence of H2O2, Ag-HA could catalyze the generation of reactive oxygen species radicals, effectively oxidizing the colorless chromogenic substrate o-phenylenediamine (OPD) into the yellow oxidized product 2,3-diaminophenazine (DAP), which exhibited fluorescence emission at 570 nm and had a characteristic absorption peak at 415 nm. Meanwhile, due to the inner filter effect (IFE), DAP could quench the blue fluorescence of Ag-HA. The addition of DA hindered the oxidation of OPD, thereby reducing DAP formation and consequently decreasing its fluorescence and absorption signals, while recovering the blue fluorescence of Ag-HA in the system. Thus, a dual-signal detection platform was established for the determination of DA concentration by monitoring changes in the fluorescence intensity ratio (F442/F570) and colorimetric signal, with detection limits (LOD) of 0.035 μM and 0.23 μM, respectively. In addition, the proposed dual-mode strategy has achieved good practicability and application prospects in agarose hydrogel-smartphone visualization for detecting DA.

The high carbonization of carbon-based nanozymes makes them have poor hydrophilicity, and the dispersion in aqueous solution or biological medium is not ideal, which restrains their applications. In this work, we synthesized a novel ultra-thin copper/nitrogen doped carbon coated with Mo2N nanoparticles (Mo2N@CuNC) by pyrolysis of two-dimension Mo/Cu@ZIF, which was obtained via ion exchange using Na2MoO4 as the secondary metal source and morphology regulator on the basis of Cu@ZIF-L. Mo2N@CuNC showed significantly improved water dispersibility and excellent peroxidase-like and ascorbic acid oxidase-like activity. Based on the dual-enzyme mimicking activities of Mo2N@CuNC, a ratiometric colorimetric sensing platform for nitrite determination and a ratiometric fluorometric sensing platform for highly selective ascorbic acid determination were designed, respectively. Additionally, smartphone-assisted visual detection was successfully realized, demonstrating the great application prospects of dual-enzyme mimics in food and environmental analysis.

Herein, a dual-mode fluorometric and colorimetric biosensor for Pax-5a gene was developed based on zinc-doped molybdenum disulfide quantum dots (Zn-MoS2 QDs) by coupling exonuclease-assisted recycling amplification and peroxidase-mimic DNAzyme. In the presence of Pax-5a gene, the exonuclease III can cleave the duplexes formed by Pax-5a gene and the hairpin DNA (HP), releasing the output DNA (oDNA). G-rich DNA and magnetic beads (MBs) labeled with capture DNA (cDNA) can hybridize with oDNA to form the MBs-cDNA/oDNA/G-rich DNA sandwich complex. The remaining G-rich DNA in the supernatant through magnetic separation could bind hemin to produce G-quadruplex/hemin peroxidase-mimicking DNAzyme, which catalyzed the oxidization of 3,3 ' diaminobenzidine (DAB) by H2O2. The generated brown oxidation product (oxDAB) had a distinct absorption peak at 464 nm and could quench the fluorescence of Zn-MoS2 QDs at 406 nm. The high peroxidase activity of DNAzyme, recycling amplification strategy and magnetic separation technique led to excellent sensitivity and specificity of this detection platform. The detection limits of Pax-5a gene by fluorometric and colorimetric methods were 0.52 pM and 1.12 pM, respectively. Furthermore, this sensing system was successfully applied to Pax-5a gene determination in human serum samples, which had promising potential in biochemical analysis and clinical diagnosis.

Single-atom nanozymes (SANs) gain considerable attention in the construction of analytical sensing platforms because of their superior stability and atom utilization. Herein, a novel nitrogen-doped carbon-based molybdenum single-atom nanozyme (Mo/NC-SAN) with excellent peroxidase-like activity is synthesized by pyrolysis process of Mo-doped metal-organic frameworks (Mo@ZIF-8). Due to the space-confinement effect of metal--organic framework and synergy of heteroatoms, Mo atoms are uniformly dispersed in the Mo/NC-SAN leading to more active sites. The wrinkled and rough surfaces of Mo/NC-SAN with porous structures increase the specific surface area. Therefore, Mo/NC-SAN possesses excellent catalytic efficiency. Furthermore, Mo/NC-SAN and silver nanoclusters (AgNCs) with high stability and fluorescence intensity are strategically integrated to construct a sensitive dual-mode sensing platform for neurotransmitter epinephrine (EP) detection. When hydrogen peroxide (H2O2) is present, the Mo/NC-SAN can catalyze the oxidation of colorless EP to adrenochrome, which produces absorbance at 485 nm. Meanwhile, because of the inner-filter effect (IFE) between AgNCs and adrenochrome, the fluorescence of AgNCs at 474 nm can be efficiently quenched by adrenochrome. When EP concentration continuously increases, the absorption intensity of adrenochrome progressively increases at 485 nm and AgNCs fluorescence at 474 nm gradually reduces. The fluorescence and colorimetric sensing systems both respond sensitively to the EP concentration in the range of 2-500 mu M and 5-500 mu M, with the limit of detection 0.35 mu M and 0.42 mu M, respectively. Furthermore, the proposed detection platform with satisfactory results for the EP measurement is successfully validated in human serum samples.

To ensure a sensitive and accurate assessment of potential health hazards posed by tertiary butylhydroquinone (TBHQ) in food products, we developed a novel ratiometric fluorescence-colorimetric dual-mode sensing system for TBHQ monitoring, which integrated copper‑cerium oxide nanocubes (Cu-CeO2 NCs) with nitrogen-doped carbon dots (N-CDs). The Cu-CeO2 NCs with excellent peroxidase-like activity could catalyze the H2O2-mediated oxidation of o-phenylenediamine (OPD) to fluorescent 2,3-diaminophenothiazine (DAP). The DAP exhibited ultraviolet absorption at 415 nm with fluorescence emission at 565 nm, that could quench the fluorescence of N-CDs at 469 nm via inner filter effect. TBHQ with strong antioxidant capacity inhibited the oxidation of OPD, thus restoring the fluorescence of N-CDs. Therefore, a dual-mode sensing platform was established for TBHQ analysis with the limits of detection of 0.64 and 0.81 μg/mL, respectively. This platform demonstrated good practicability through its successful implementation in detecting TBHQ in edible oils.

Neurodegenerative diseases such as Parkinson's and Alzheimer's are closely associated with abnormal dopamine (DA) fluctuating, it is the critical need for sensitive and accurate DA detection for early diagnosis. Herein, we rationally designed a hierarchical nanoarchitecture by in situ growing NiMn-layered double hydroxide (NiMnLDH) nanosheets onto exfoliated MXene (eM) substrates. The resulting NiMn-LDH-eM exhibited robust oxidaselike activity, achieving a high oxidase activity of 3.6 U mg(-1) owing to abundant catalytic centers and intimate interfacial coupling. Furthermore, a tri-modal DA sensing platform was developed, which integrating UV-vis absorbance, silicon quantum dots (Si-QDs)-assisted ratiometric fluorescence, and electrochemical quantification. Upon DA addition, the competitive oxidation pathway reduces 2,3-diaminophenazine (DAP) generation, leading to a progressive decrease in the F565/F453 ratio in the fluorescence spectrum. Simultaneously, the characteristic UV-vis absorption peak of DAP at 450 nm weakens, while the electrochemical oxidation of DA induces a pronounced enhancement in current response, confirming a multi-modal response induced by DA. This study provides a promising framework for constructing multifunctional nanozyme platforms for neurochemical diagnostics.