Highly active nanozyme based on nitrogen-doped graphene quantum dots and iron ion nanocomposite for selective colorimetric detection of hydroquinone.

Inspired by the iron porphyrin structure of natural horseradish peroxidase (HRP), an efficient carbon-based nanozyme was fabricated using nitrogen-doped graphene quantum dots (NGQDs) and iron ion (Fe3+) nanocomposite, enabling selective distinguishment of hydroquinone (HQ) from its isomers. NGQDs with good dispersibility and uniform size were synthesized via a one-step hydrothermal process. NGQDs lacked peroxidase-like activity but the formed nanocomposite (Fe3+-NGQDs) upon Fe3+ addition possessed high peroxidase-like activity. Fe3+-NGQDs nanocomposite exhibited shuttle-shaped structure (∼30 nm), the lattice structure of NGQDs and electron transfer between Fe3+ and NGQDs. The Fe3+-NGQDs nanocomposite can catalyze the production of superoxide radicals (•O2-) from H2O2. The Michaelis constant (Km) of Fe3+-NGQDs (0.115 mM) was lower than that of natural HRP (0.434 mM) with 3,3',5,5'-tetramethylbenzidine (TMB) as the substrate and the maximum initial reaction rate (Vmax, 16.47 × 10-8 M/s) was nearly 4 times higher than that of HRP using H2O2 substrate. HQ, unlike its isomers catechol (CC) and resorcinol (RE), could consume •O2- generated from the decomposition of H2O2 catalyzed by Fe3+-NGQDs nanocomposite, reducing the oxidation of TMB. This principle enabled selective colorimetric determination of HQ ranged from 1 µM to 70 µM and a limit of detection (LOD) of 0.2 µM. Successful determination of HQ in pond water was also realized.

Machine learning-enabled colorimetric sensors for foodborne pathogen detection.

In the past decade, there have been various advancements to colorimetric sensors to improve their potential applications in food and agriculture. One application of growing interest is sensing foodborne pathogens. There are unique considerations for sensing in the food industry, including food sample destruction, specificity amidst a complex food matrix, and high sensitivity requirements. Incorporating novel technology, such as nanotechnology, microfluidics, and smartphone app development, into colorimetric sensing methodology can enhance sensor performance. Nonetheless, there remain challenges to integrating sensors with existing food safety infrastructure. Recently, increasingly advanced machine learning techniques have been employed to facilitate nondestructive, multiplex detection for feasible assimilation of sensors into the food industry. With its ability to analyze and make predictions from highly complex data, machine learning holds potential for advanced yet practical colorimetric sensing of foodborne pathogens. This article summarizes recent developments and hurdles of machine learning-enabled colorimetric foodborne pathogen sensing. These advancements underscore the potential of interdisciplinary, cutting-edge technology in providing safer and more efficient food systems.

Dithiothreitol-functionalized perovskite-based visual sensing array capable of distinguishing food oils.

At present, the combination of fingerprint recognition methods and environmentally friendly and economical analytical instruments is becoming increasingly important in the food industry. Herein, a dithiothreitol (DTT)-functionalized CsPbBr3-based colorimetric sensor array is developed for qualitatively differentiating multiple food oils. In this sensor array composition, two types of iodides (octadecylammonium iodide (ODAI) and ZnI2) are used as recognition elements, and CsPbBr3 is used as a signal probe for the sensor array. Different food oils oxidize iodides differently, resulting in different amounts of remaining iodides. Halogen ion exchange occurs between the remaining iodides and CsPbBr3, leading to different colors observed under ultraviolet light, enabling a unique fingerprint for each food oil. A total of five food oils exhibit their unique colorimetric array's response patterns and were successfully differentiated by linear discriminant analysis (LDA), realizing 100% classification accuracy.

Integrated Sensing Platform Validated for the Efficient and On-Site Screening of Amine-Containing Illicit Drugs.

Efficient and reliable technologies for the on-site detection of illicit drugs are important in drug-facilitated crime investigations. However, the development of such technologies is challenging. Based on the synthetic optimization, introducing a boron ester functional group to the two furanic indicators endows the stimulus-responsive properties synergistically. The ring-opening reaction of the indicators in the presence of amine-containing illicit drugs generated well-known donor-acceptor Stenhouse adducts, accompanied by strong color changes. A small-size and lightweight laminated sensor was integrated based on the outstanding ratiometric variations of the two active furanic indicators. A prototype platform was fabricated equipped with a circuit control, a mini pump, and a signal processing system. A user-friendly detection and efficient screening of amine-containing illicit drugs, including phenethylamines, amphetamines, cathinones, and tryptamines in the liquid states were conducted. The ratiometric response of the sensor was linear in the concentration range of 2.1-10.6 µg·mL-1 for methamphetamine·HCl and methcathinone ·HCl. The detection limits for the two illicit drugs at the sublevel (ng·mL-1) were found to be 8.4 and 9.0 ng·mL-1, respectively. Double-blind field tests and different illicit drugs were evaluated with good screening capability. Successful trials showed the potential applications of the developed prototype platform for efficient and on-site analytical determination.

Label-free colorimetric analysis strategies based on adsorption-responsive surface-enhanced photochromic phenomena of tungsten(VI) oxide nanoparticles for amino acids.

Herein, we present a colorimetric detection method based on the surface-enhanced photochromic phenomenon of tungsten (VI) oxide (WO3) nanocolloid particles for α-amino acid (AA) molecules, including L-aspartic acid (Asp), L-glutamic acid (Glu), L-histidine (His), L-isoleucine (Ile), L-leucine (Leu), L-lysine (Lys), L-phenylalanine (Phe), and L-valine (Val). The UV-induced photochromic phenomena in the AA/WO3 binary aqueous systems were investigated using UV-Vis absorption spectrometry. The adsorption properties of the AA molecules on the surface of the WO3 nanocolloid particles have been identified using a combination of adsorption isotherm analysis and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. A good linear correlation between the concentration of the AAs adsorbed on the surface of the WO3 nanocolloid particles and the initial photochromic coloration rate in the corresponding UV-irradiated WO3 colloidal aqueous solution was obtained with over three orders of magnitude, indicating that the surface-enhanced photochromic phenomenon of the WO3 nanocolloid particle can be used to detect the AA molecules. In addition, based on the results of the UV-Vis absorption, ATR-FTIR, and adsorption isotherm analyses, we have experimentally demonstrated that the AA/WO3 binary aqueous system with inner-sphere adsorbed Ile, Leu, Lys, or Val molecules on the surface of the WO3 nanocolloid particles exhibits a more significant surface-enhanced photochromic phenomenon than the system with outer-sphere adsorbed Asp, Glu, His, or Phe molecules. The strong inner-sphere adsorption of the AA molecules successfully improved the limit of detection. This study provides valuable insights into a "label-free" colorimetric assay system based on the surface-enhanced photochromic phenomenon of the WO3 nanocolloid probe.

Ultrasmall CuMn-His Nanozymes with Multienzyme Activity at Neutral pH: Construction of a Colorimetric Sensing Array for Biothiol Detection and Disease Identification.

Biothiol assays offer vital insights into health assessment and facilitate the early detection of potential health issues, thereby enabling timely and effective interventions. In this study, we developed ultrasmall CuMn-Histidine (His) nanozymes with multiple enzymatic activities. CuMn-His enhanced peroxidase (POD)-like activity at neutral pH was achieved through hydrogen bonding and electrostatic effects. In addition, CuMn-His possesses laccase (LAC)-like and superoxide dismutase (SOD)-like activities at neutral pH. Based on three different enzyme mimetic activities of CuMn-His at neutral pH, the colorimetric sensing array without changing the buffer solution was successfully constructed. The array was successfully used for the identification of three biothiols, glutathione (GSH), cysteine (Cys), and homocysteine (Hcy). Subsequently, excellent application results were shown in complex serum and cellular level analyses. This study provides an innovative strategy for the development of ultrasmall bimetallic nanozymes with multiple enzymatic activities and the construction of colorimetric sensing arrays.

Advances in Nanomaterials and Colorimetric Detection of Arsenic in Water: Review and Future Perspectives.

Arsenic, existing in various chemical forms such as arsenate (As(V)) and arsenite (As(III)), demands serious attention in water and environmental contexts due to its significant health risks. It is classified as "carcinogenic to humans" by the International Agency for Research on Cancer (IARC) and is listed by the World Health Organization (WHO) as one of the top 10 chemicals posing major public health concerns. This widespread contamination results in millions of people globally being exposed to dangerous levels of arsenic, making it a top priority for the WHO. Chronic arsenic toxicity, known as arsenicosis, presents with specific skin lesions like pigmentation and keratosis, along with systemic manifestations including chronic lung diseases, liver issues, vascular problems, hypertension, diabetes mellitus, and cancer, often leading to fatal outcomes. Therefore, it is crucial to explore novel, cost-effective, and reliable methods with rapid response and improved sensitivities (detection limits). Most of the traditional detection techniques often face limitations in terms of complexity, cost, and the need for sophisticated equipment requiring skilled analysts and procedures, which thereby impedes their practical use, particularly in resource-constrained settings. Colorimetric methods leverage colour changes which are observable and quantifiable using simple instrumentation or even visual inspection. This review explores the colorimetric techniques designed to detect arsenite and arsenate in water. It covers recent developments in colorimetric techniques, and advancements in the role of nanomaterials in colorimetric arsenic detection, followed by discussion on current challenges and future prospects. The review emphasizes efforts to improve sensitivity, selectivity, cost, and portability, as well as the role of advanced materials/nanomaterials to boost the performance of colorimetric assays/sensors towards combatting this pervasive global health concern.

Remote-Controlled Sensing and Drug Delivery via 3D-Printed Hollow Microneedles.

Remote health monitoring and treatment serve as critical drivers for advancing health equity, bridging geographical and socioeconomic disparities, ensuring equitable access to quality healthcare for those in underserved or remote regions. By democratizing healthcare, this approach offers timely interventions, continuous monitoring, and personalized care independent of one's location or socioeconomic status, thereby striving for an equitable distribution of health resources and outcomes. Meanwhile, microneedle arrays (MNAs), revolutionize painless and minimally invasive access to interstitial fluid for drug delivery and diagnostics. This paper introduces an integrated theranostic MNA system employing an array of colorimetric sensors to quantitatively measure -pH, glucose, and lactate, alongside a remotely-triggered system enabling on-demand drug delivery. Integration of an ultrasonic atomizer streamlines the drug delivery, facilitating rapid, pumpless, and point-of-care drug delivery, enhancing system portability while reducing complexities. An accompanying smartphone application interfaces the sensing and drug delivery components. Demonstrated capabilities include detecting pH (3 to 8), glucose (up to 16 mm), and lactate (up to 1.6 mm), showcasing on-demand drug delivery, and assessing delivery system performance via a scratch assay. This innovative approach confronts drug delivery challenges, particularly in managing chronic diseases requiring long-term treatment, while also offering avenues for non-invasive health monitoring through microneedle-based sensors.

MOF derivatization of multifunctional nanozyme: Peroxidase-like catalytic activity combined with magnetic solid phase extraction for colorimetric detection of Hg2.

Nanozyme-based colorimetric sensing has drawn immense attention due to the rapid development of nanozyme in recent years. However, the selectivity of nanozyme-based colorimetric sensing greatly limits its subsequent practical application. It is well known that sample pretreatment can not only improve selectivity by eliminating the sample matrix interference, but also improve sensitivity by enriching trace targets. Based on the easy facile surface modification properties of nanozyme, we rationally designed nanozyme combined with sample pretreatment for colorimetric biosensing, through separation and enrichment, thereby improving the selectivity and sensitivity of the nanozyme colorimetric biosensing. As a proof of concept, the detection of Hg2+ by nanozyme-based colorimetric sensing was used as an example. Magnetic peroxidase-like nanozyme Fe3S4 was designed and synthesized. The selectivity is improved by the specific adsorption of S-Hg bond and the interference elimination after magnetic separation. In addition, the sensitivity is improved by magnetic solid-phase extraction enrichment. Our established colorimetric sensing based on Fe3S4 nanozyme integrated sample pretreatment with an enrichment factor of 100 and the limit of detection (LOD) is 26 nM. In addition, this strategy was successfully applied to detect Hg2+ in environmental water samples. Overall, the strategy showed good selectivity and sensitivity, providing a new practical method for the application of nanozyme-based biosensing in sample pretreatment.

A facile nanozyme-based colorimetric method to realize the quantitative and specific detection of casein phosphopeptides in food samples.

As a popular nutritional enhancer, casein phosphopeptides (CPPs) have attracted growing attention in food industry. However, conventional methods for CPPs detection are usually less precise or requires expensive instruments. Herein, a nanozyme-based colorimetric method was developed to achieve the quantitative detection of CPPs in food samples. This method is based on a facilely fabricated peroxidase-like nanozyme (Fe@UiO-66), which combines the specific binding of CPPs, as well as the nanozyme-catalyzed colorimetric sensing that can be easily detected by spectrometer. The method displayed good quantitative ability toward CPPs with the linear range of 2-30 µg/mL, the low limit of detection of 0.267 µg/mL and limit of quantification of 1.335 µg/mL. We highlighted the specificity, anti-interference and practicability of this method, by investigating the performances toward food samples. Besides, a smartphone-based colorimetric sensing platform was also established, which is conducive to the portable detection. The developed nanozyme-based colorimetric sensing method provides a promising strategy for CPPs detection in food samples.

A sensitive Ag+-mediated magnetic relaxation and colorimetry dual-mode sensing platform.

To address the relatively low sensitivity of current redox reagent-mediated magnetic relaxation sensing methods, we present a novel Ag+-mediated magnetic sensing platform that enhances the sensitivity by three orders of magnitude. The new sensing platform is based on Ag+-catalyzed oxidation of Mn2+ to KMnO4, accompanied by a distinct color change, which facilitates colorimetric detection. In the case of insufficient Ag+ ions, MnO2 is an additional oxidation product and the KMnO4/MnO2 ratio is dependent on the concentration of Ag+. When combined with a specific quantity of reducing agent, both KMnO4 and MnO2 are reduced to Mn2+ with a large relaxivity, and the concentration of Mn2+ in the resultant solution inversely correlates with the amount of KMnO4 since KMnO4 consumes more reductant during reduction. Consequently, the transverse relaxation rate of the solution exhibits a negative correlation with the Ag+ concentration. Thus, by coupling this Ag+-mediated Mn2+ to KMnO4 transformation with reactions that modulate Ag+ concentration, a dual-mode sensing platform for magnetic relaxation and colorimetry can be realized. Herein, we take H2O2 as an example to verify the detection performance of this sensing platform since H2O2 can oxidize Ag0 in Ag@Fe3O4 nanoparticles to Ag+. Experimental findings demonstrate detection limits of 10 nM and 20 nM for the magnetic relaxation and colorimetry modes, respectively, affirming the excellent sensitivity and the potential practical application of this strategy.

Smart Contact Lens for Colorimetric Visualization of Glucose Levels in the Body Fluid.

Frequent blood glucose monitoring is a crucial routine for diabetic patients. Traditional invasive methods can cause discomfort and pain and even pose a risk of infection. As a result, researchers have been exploring noninvasive techniques. However, a limited number of products have been developed for the market due to their high cost. In this study, we developed a low-cost, highly accessible, and noninvasive contact lens-based glucose monitoring system. We functionalized the surface of the contact lens with boronic acid, which has a strong but reversible binding affinity to glucose. To achieve facile conjugation of boronic acid, we utilized a functional coating layer called poly(tannic acid). The functionalized contact lens binds to glucose in body fluids (e.g., tear) and releases it when soaked in an enzymatic cocktail, allowing for the glucose level to be quantified through a colorimetric assay. Importantly, the transparency and oxygen permeability of the contact lens, which are crucial for practical use, were maintained after functionalization, and the lenses showed high biocompatibility. Based on the analysis of colorimetric data generated by the smartphone application and ultraviolet-visible (UV-vis) spectra, we believe that this contact lens has a high potential to be used as a smart diagnostic tool for monitoring and managing blood glucose levels.

Zirconium-porphyrin-MOF-based oxidase-like nanozyme with oxygen vacancy for aflatoxin B1 colorimetric sensing.

In this study, a porous coordination network zirconium-porphyrin-based nanoparticle with oxygen vacancies (OVs) was prepared using acetic acid and benzoic acid as modulators via a simple hydrothermal method. The presence of OVs was confirmed by various characterization methods and was found to enhance oxygen uptake and activation. This resulted in the generation of more reactive peroxyl radicals (•O2 -) and led to an improved oxidase (OXD) mimetic activity. Additionally, it promoted 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) oxidation, with a low Km value of 0.07 mM and a high Vmax of 1.47 × 10-7 M·s-1. As aflatoxin B1 (AFB1) inhibits the Pt@PCN-222-ABTS nanozyme system, a colorimetric probe for AFB1 detection was constructed. The limit of detection (LOD) was 0.074 µg·L-1. This research presents a novel approach for designing a nanozymatic-based colorimetric method to analyze trace AFB1 residues in food.

GAA/(Au-Au/IrO2)@Cu(PABA) reactor with cascade catalytic activity for α-glucosidase inhibitor screening.

BACKGROUND: In vitro screening strategies based on the inhibition of α-glucosidase (GAA) activity have been widely used for the discovery of potential antidiabetic drugs, but they still face some challenges, such as poor enzyme stability, non-reusability and narrow range of applicability. To overcome these limitations, an in vitro screening method based on GAA@GOx@Cu-MOF reactor was developed in our previous study. However, the method was still not satisfactory enough in terms of construction cost, pH stability, organic solvent resistance and reusability. Thence, there is still a great need for the development of in vitro screening methods with lower cost and wider applicability. RESULTS: A colorimetric sensing strategy based on GAA/(Au-Au/IrO2)@Cu(PABA) cascade catalytic reactor, which constructed through simultaneous encapsulating Au-Au/IrO2 nanozyme with glucose oxidase-mimicking and peroxidase-mimicking activities and GAA in Cu(PABA) carrier with peroxidase-mimicking activity, was innovatively developed for in vitro screening of GAA inhibitors in this work. It was found that the reactor not only exhibited excellent thermal stability, pH stability, organic solvent resistance, room temperature storage stability, and reusability, but also possessed cascade catalytic performance, with approximately 12.36-fold increased catalytic activity compared to the free system (GAA + Au-Au/IrO2). Moreover, the in vitro GAA inhibitors screening method based on this reactor demonstrated considerable anti-interference performance and detection sensitivity, with a detection limit of 4.79 nM for acarbose. Meanwhile, the method owned good reliability and accuracy, and has been successfully applied to the in vitro screening of oleanolic acid derivatives as potential GAA inhibitors. SIGNIFICANCE: This method not only more effectively solved the shortcomings of poor stability, narrow scope of application, and non-reusability of natural enzymes in the classical method compared with our previous work, but also broaden the application scope of Au-Au/IrO2 nanozyme with glucose oxidase and peroxidase mimicking activities, and Cu(PABA) carrier with peroxidase mimicking activity, which was expected to be a new generation candidate method for GAA inhibitor screening.

Integrated Fruit Ripeness Assessment System Based on an Artificial Olfactory Sensor and Deep Learning.

Artificial scent screening systems, inspired by the mammalian olfactory system, hold promise for fruit ripeness detection, but their commercialization is limited by low sensitivity or pattern recognition inaccuracy. This study presents a portable fruit ripeness prediction system based on colorimetric sensing combinatorics and deep convolutional neural networks (DCNN) to accurately identify fruit ripeness. Using the gas chromatography-mass spectrometry (GC-MS) method, the study discerned the distinctive gases emitted by mango, peach, and banana across various ripening stages. The colorimetric sensing combinatorics utilized 25 dyes sensitive to fruit volatile gases, generating a distinct scent fingerprint through cross-reactivity to diverse concentrations and varieties of gases. The unique scent fingerprints can be identified using DCNN. After capturing colorimetric sensor image data, the densely connected convolutional network (DenseNet) was employed, achieving an impressive accuracy rate of 97.39% on the validation set and 82.20% on the test set in assessing fruit ripeness. This fruit ripeness prediction system, coupled with a DCNN, successfully addresses the issues of complex pattern recognition and low identification accuracy. Overall, this innovative tool exhibits high accuracy, non-destructiveness, practical applicability, convenience, and low cost, making it worth considering and developing for fruit ripeness detection.

Extensive optical and DFT studies on novel AIE active fluorescent sensor for Colorimetric and fluorometric detection of nitrobenzene in Solid, solution and vapor phase.

An electron rich isophthalamide based sensor IPA has been synthesized through a simple two-step reaction, containing noteworthy aggregation induced emission (AIE) properties. Considering the significant emission with λmax at 438 nm, sensor IPA has been employed for the sensing of nitrobenzene (NB) in solid, solution and vapor state with high sensitivity and selectivity. Sensor IPA showed noteworthy colorimetric and fluorometric quenching in fluorescence emission when exposed to NB. Small size of NB and involvement of photoinduced electron transfer (PET) lead to detection of NB down to 60 nM. IPA-NB interaction was studied through UV-Vis. spectroscopic studies along with fluorescence spectroscopy. Moreover, 1H and 13C NMR titration experiments provided additional support for determination of interaction type. Furthermore, by using density functional theory (DFT) calculations, thermodynamic stability was studied. Additionally, non-covalent interactions (NCI), frontier molecular orbitals (FMO), density of states (DOS), were investigated for providing further evidence of nitrobenzene sensing and its interaction with sensor. Natural bond orbital (NBO) analysis was carried out for charge transfer studies. Quantum theory of atom in molecule (QTAIM) and SAPT0 studies provided information about interaction points and binding energy. Additionally, IPA was investigated for NB sensing in real water samples, and its effective participation in solid state on-site detection as well as in solution phase was brought to light along with logic gate construction.

Copper regulation of PtRhRuCu nanozyme targeted boosting peroxidase-like activity for ultrasensitive smartphone-assisted colorimetric sensing of glucose.

Point-of-care testing (POCT) is promising for biodetection in home healthcare due to advantages of simplicity, rapidity, low cost, portability, high sensitivity and accuracy, and object-oriented POCT platform can be developed by nanozyme-based biosensing. However, designing high-performance nanozymes with targeted regulated catalytic activity remains challenging. Herein, advanced PtRhRuCu quaternary alloy nanozymes (QANs) were rationally designed and successfully synthesized. Cu atoms induced mechanisms of hydrogen peroxide (H2O2) activation and d-band center regulation, achieving high enhancement of peroxide (POD)-like activity and inhibition of oxidase (OXD)-like activity. Inspired by this, a smartphone-assisted colorimetric platform integrated with test strips was established for glucose detection of soft drinks, with a detection limit of 0.021 mM and a recovery rate of 97.87 to 103.36 %. This work not only provides a novel path for tuning specific enzyme-like activities of metal nanozymes, but also shows the potential feasibility for rational design of POCT sensors in actual samples.

A portable colorimetric sensing platform for rapid and sensitive quantification of dichlorvos pesticide based on Fe-Mn bimetallic oxide nanozyme-participated highly efficient chromogenic catalysis.

BACKGROUND: Dichlorvos (DDVP), as a highly effective insecticide, is widely used in agricultural production. However, DDVP residue in foodstuffs adversely affects human health. Conventional instrumental analysis can provide highly sensitive and accurate detection of DDVP, while the need of bulky and expensive equipment limits their application in resource-poor areas and on-site detection. Therefore, the development of easily portable sensing platforms for convenient, rapid and sensitive quantification of DDVP is very essential for ensuring food safety. RESULT: A portable colorimetric sensing platform for rapid and sensitive quantification of DDVP is developed based on nanozyme-participated highly efficient chromogenic catalysis. The Fe-Mn bimetallic oxide (FeMnOx) nanozyme possesses excellently oxidase-like activity and can efficiently catalyze oxidation of 3, 3', 5, 5'-tetramethylbenzidine (TMB) into a blue oxide with a very low Michaelis constant (Km) of 0.0522 mM. The nanozyme-catalyzed chromogenic reaction can be mediated by DDVP via inhibiting the acetylcholinesterase (AChE) activity. Thus, trace DDVP concentration-dependent color evolution is achieved and DDVP can be sensitively detected by spectrophotometry. Furthermore, a smartphone-integrated 3D-printed miniature lightbox is fabricated as the colorimetric signal acquisition and processing device. Based on the FeMnOx nanozyme and smartphone-integrated lightbox system, the portable colorimetric sensing platform of DDVP is obtained and it has a wide linear range from 1 to 3000 ng mL-1 with a low limit of detection (LOD) of 0.267 ng mL-1 for DDVP quantification. SIGNIFICANCE: This represents a new portable colorimetric sensing platform that can perform detection of DDVP in foodstuffs with simplicity, sensitivity, and low cost. The work not only offers an alternative to rapid and sensitive detection of DDVP, but also provides a new insight for the development of advanced sensors by the combination of nanozyme, 3D-printing and information technologies.

Research Progress on the Application of Nanocellulose in Glucose Sensing.

BACKGROUND: Nanocellulose is not only a biocompatible and environmentally friendly material but also has excellent mechanical properties, biodegradability, and a large number of hydroxyl groups that have a strong affinity for water. These characteristics have attracted significant attention from researchers in the field of glucose sensing. OBJECTIVE: This review provides a brief overview of the current research status of traditional materials used in glucose sensors. The sensing performance, chemical stability, and environ-mental properties of nanocellulose-based glucose sensors are compared and summarized based on the three sensing methods: electrochemical sensing, colorimetric sensing, and fluo-rescence sensing. The article focuses on recent strategies for glucose sensing using nanocel-lulose as a matrix. The development prospects of nanocellulose-based glucose sensors are also discussed. CONCLUSION: Nanocellulose has outstanding structural characteristics that contribute signifi-cantly to the sensing performance of glucose sensors in different detection modes. However, the preparation process for high-quality nanocellulose is complicated and has a low yield. Furthermore, the sensitivity and selectivity of nanocellulose-based glucose sensors require further improvement.

Imine-Linked 2D Conjugated Porous Organic Polymer Films for Tunable Acid Vapor Sensing.

Two-dimensional (2D) films of conjugated porous organic polymers (C-POPs) can translate the rich in-plane functionalities of conjugated frameworks into diverse optical and electronic applications while addressing the processability issues of their crystalline analogs for adaptable device architectures. However, the lack of facile single-step synthetic routes to obtain large-area high-quality films of 2D-C-POPs has limited their application possibilities so far. Here, we report the synthesis of four mechanically robust imine-linked 2D-C-POP free-standing films using a single-step fast condensation route that is scalable and tunable. The rigid covalently bonded 2D structures of the C-POP films offer high stability for volatile gas sensing in harsh environments while simultaneously enhancing site accessibility for gas molecules due to mesoporosity by structural design. Structurally, all films were composed of exfoliable layers of 2D polymeric nanosheets (NSs) that displayed anisotropy from disordered stacking, evinced by out-of-plane birefringent properties. The tunable in-plane conjugation, different nitrogen centers, and porous structures allow the films to act as ultraresponsive colorimetric sensors for acid sensing via reversible imine bond protonation. All the films could detect hydrogen chloride (HCl) gas down to 0.05 ppm, far exceeding the Occupational Safety and Health Administration's permissible exposure limit of 5 ppm with fast response time and good recyclability. Computational insights elucidated the effect of conjugation and tertiary nitrogen in the structures on the sensitivity and response time of the films. Furthermore, we exploited the exfoliated large 2D NSs and anisotropic optoelectronic properties of the films to adapt them into micro-optical and triboelectric devices to demonstrate their real-time sensing capabilities.