Paper-based vapor detection of hydrogen peroxide: colorimetric sensing with tunable interface

A H2O2 Self-Charging Zinc Battery with Ultrafast Power Generation and Storage

Self-charging power systems are considered as promising alternatives for off-grid energy devices to provide sustained electricity supply. However, the conventional self-charging systems are severely restricted by the energy availability and time-consuming charging process as well as insufficient capacity. Herein, we developed an ultrafast H2O2 self-charging aqueous Zn/NaFeFe(CN)6 battery, which simultaneously integrates the H2O2 power generation and energy storage into a battery configuration. In such battery, the chemical energy conversion of H2O2 can generate electrical energy to self-charge the battery to 1.7 V through the redox reaction between H2O2 and NaFeFe(CN)6 cathode. The thermodynamically and kinetically favorable redox reaction contributes to the ultrafast H2O2 self-charging rate and the extremely short self-charging time within 60 seconds. Moreover, the rapid H2O2 power generation can promptly compensate the energy consumption of battery to provide continuous electricity supply. Impressively, this self-charging battery shows excellent scalability of device architecture and can be designed to a H2O2 single-flow battery of 7.06 Ah to extend the long-term energy supply. This work not only provides a route to design self-charging batteries with fast charging rate and high capacity, but also pushes forward the development of self-charging power systems for advanced large-scale energy storage applications.

Fluorescence Turn-on Detection of Perfluorooctanoic Acid (PFOA) by Perylene Diimide-Based Metal-Organic Framework

A novel, water-stable, perylene diimide (PDI) based metal-organic framework (MOF), namely, U-1, has been synthesized for selective and sensitive detection of perfluorooctanoic acid (PFOA) in mixed aqueous solutions. The MOF shows highly selective fluorescence turn-on detection via the formation of a PFOA-MOF complex. This PFOA-MOF complex formation was confirmed by various spectroscopic techniques. The detection limit of the MOF for PFOA was found to be 1.68 μM in an aqueous suspension. Upon coating onto cellulose paper, the MOF demonstrated a significantly lower detection limit, down to 3.1 nM, which is mainly due to the concentrative effect of solid phase extraction (SPE). This detection limit is lower than the fluorescence sensors based on MOFs previously reported for PFAS detection. The MOF sensor is regenerable and capable of detecting PFOA in drinking and tap water samples. The PDI-MOF-based sensor reported herein represents a novel approach, relying on fluorescence turn-on response, that has not yet been thoroughly investigated for detecting per- and polyfluoroalkyl substances (PFAS) until now.

A ferroptosis-reinforced nanocatalyst enhances chemodynamic therapy through dual H2O2 production and oxidative stress amplification

The existence of a delicate redox balance in tumors usually leads to cancer treatment failure. Breaking redox homeostasis by amplifying oxidative stress and reducing glutathione (GSH) can accelerate cancer cell death. Herein, we construct a ferroptosis-reinforced nanocatalyst (denoted as HBGL) to amplify intracellular oxidative stress via dual H2O2 production-assisted chemodynamic therapy (CDT). Specifically, a long-circulating liposome is employed to deliver hemin (a natural iron-containing substrate for Fenton reaction and ferroptosis), β-lapachone (a DNA topoisomerase inhibitor with H2O2 generation capacity for chemotherapy), and glucose oxidase (which can consume glucose for starvation therapy and generate H2O2). HBGL can achieve rapid, continuous, and massive H2O2 and •OH production and GSH depletion in cancer cells, resulting in increased intracellular oxidative stress. Additionally, hemin can reinforce the ferroptosis-inducing ability of HBGL, which is reflected in the downregulation of glutathione peroxidase-4 and the accumulation of lipid peroxide. Notably, HBGL can disrupt endo/lysosomes and impair mitochondrial function in cancer cells. HBGL exhibits effective tumor-killing ability without eliciting obvious side effects, indicating its clinical translation potential for synergistic starvation therapy, chemotherapy, ferroptosis therapy, and CDT. Overall, this nanocatalytic liposome may be a promising candidate for achieving potentiated cancer treatment.

Recent Advances in Construction Strategies for Fluorescence Sensing Films

A year ago, film-based fluorescent sensors (FFSs) were recognized in the "IUPAC Top Ten Emerging Technologies in Chemistry 2022" due to their extensive application in detecting hidden explosives, illicit drugs, and volatile organic compounds. These sensors offer high sensitivity, specificity, immunity to light scattering, and noninvasiveness. The core of FFSs is the construction of high-performance fluorescent sensing films, which are dependent on the processes of "energy transfer" and "mass transfer" in the active layer and involve complex interactions between sensing molecules and analytes. This Perspective focuses on the latest strategies in constructing these films, emphasizing the design of sensing molecules with various innovative features and structures that enhance the mass transfer efficiency. Additionally, it discusses the ongoing challenges and potential advancements in the field of FFSs.

Deep Learning-Enabled Multiplexed Point-of-Care Sensor using a Paper-Based Fluorescence Vertical Flow Assay

Multiplexed computational sensing with a point-of-care serodiagnosis assay to simultaneously quantify three biomarkers of acute cardiac injury is demonstrated. This point-of-care sensor includes a paper-based fluorescence vertical flow assay (fxVFA) processed by a low-cost mobile reader, which quantifies the target biomarkers through trained neural networks, all within <15 min of test time using 50 µL of serum sample per patient. This fxVFA platform is validated using human serum samples to quantify three cardiac biomarkers, i.e., myoglobin, creatine kinase-MB, and heart-type fatty acid binding protein, achieving less than 0.52 ng mL-1 limit-of-detection for all three biomarkers with minimal cross-reactivity. Biomarker concentration quantification using the fxVFA that is coupled to neural network-based inference is blindly tested using 46 individually activated cartridges, which shows a high correlation with the ground truth concentrations for all three biomarkers achieving >0.9 linearity and <15% coefficient of variation. The competitive performance of this multiplexed computational fxVFA along with its inexpensive paper-based design and handheld footprint makes it a promising point-of-care sensor platform that can expand access to diagnostics in resource-limited settings.

A Label-Free and Ultrasensitive Prussian Blue-Based Dipstick Sensor for Bacterial and Biofilm Detection

Water and food contamination has become the major contributor to infections and deaths. However, rapid and sensitive bacterial detection still remains an unmet demand that has attracted widespread attention. Often water and food samples are sent out for laboratory testing to detect the presence of contamination, which is time-consuming and laborious. Herein, we have developed a highly sensitive, tenable, affordable, and robust (STAR) paper-based colorimetric dipstick sensor based on the principle of Prussian blue (PB) synthesis as an indicator of bacterial contamination. In the presence of bacteria, it leads to the formation of PB, a dye that acts as a colorimetric indicator. The intensity of the PB is the direct measure of the degree of contamination. The fabrication of the STAR dipstick sensor involves a simple and cost-effective process. The STAR dipstick sensor is ultrasensitive and can detect up to 101 CFU/mL of bacteria within minutes of contact with the test sample. The STAR dipstick sensor is fabricated using biodegradable components, which is speculated to facilitate quick and environmentally friendly degradation after each use. The sensor has been validated for its properties and capabilities at different pH to detect both Gram-positive and Gram-negative bacterial strains in real-time samples. The stability and degradation were also monitored. Comprehensively, the proposed STAR dipstick sensor can serve as a point-of-care device to detect bacterial contamination in a swift and sensitive manner.

A Facile Method to Fabricate an Enclosed Paper-Based Analytical Device via Double-Sided Patterning for Ionic Contaminant Detection

Microfluidic paper-based analytical devices (μPADs) have been developed for use in a variety of diagnosis and analysis fields. However, conventional μPADs with an open-channel system have limitations for application as analytical platforms mainly because of the evaporation and contamination of the sample solution. This study demonstrates the design and fabrication of an enclosed three-dimensional(3D)-μPAD and its application as a primary early analysis platform for ionic contaminants. To generate the hydrophobic PDMS barrier, double-sided patterning is carried out using a PDMS blade-coated stamp mold that is fabricated using 3D printing. The selective PDMS patterning can be achieved with controlled PDMS permeation of the cellulose substrate using 3D-designed stamp molds. We find the optimal conditions enabling the formation of enclosed channels, including round shape pattern and inter-pattern distance of 10 mm of stamp design, contact time of 0.5 min, and spacer height of 300 µm of double-sided patterning procedure. As a proof of concept, this enclosed 3D-μPAD is used for the simultaneous colorimetric detection of heavy metal ions in a concentration range of 0.1-2000 ppm, including nickel (Ni2+), copper (Cu2+), mercury (Hg2+), and radioactive isotope cesium-137 ions (Cs+). We confirm that qualitative analysis and image-based quantitative analysis with high reliability are possible through rapid color changes within 3 min. The limits of detection (LOD) for 0.55 ppm of Ni2+, 5.05 ppm of Cu2+, 0.188 ppm of Hg2+, and 0.016 ppm of Cs+ are observed, respectively. In addition, we confirm that the analysis is highly reliable in a wide range of ion concentrations with CV values below 3% for Ni2+ (0.56%), Cu2+ (0.45%), Hg2+ (1.35%), and Cs+ (2.18%). This method could be a promising technique to develop a 3D-μPAD with various applications as a primary early analysis device in the environmental and biological industries.

Platinum and palladium nanoparticles on boron-doped diamond for the electrochemical detection of hydrogen peroxide: a comparison study

Hydrogen peroxide (H2O2) plays a role in many facets - a household item, an important industrial chemical, a biomarker in vivo, and several others. For this reason, its measurement and quantification in a variety of media are important. While spectroscopic detection is primarily used for H2O2, electrochemical methods offer advantages in versatility, cost, and sensitivity. In this work, we investigate a 2-step surface metal nanoparticle (NP) modification for platinum (Pt) and palladium (Pd) on boron-doped diamond (BDD) electrodes for the detection of H2O2. Several parameters such as the metal salt concentration and electrodeposition charge in the 2-step modification were varied to find an optimum. Using cyclic voltammetry (CV), the BDD-PdNP electrode types were found to yield a sharper, more well-resolved H2O2 oxidation peak compared to the BDD-PtNP electrodes. Both metal NP electrode types significantly improved the response compared to the bare BDD electrode; a 150-200× improvement in sensitivity was observed across all modified electrode types. Calibration experiments were completed at both low and high concentration ranges in stagnant and flow-based solutions. The lowest limit of detection (LOD) obtained was 50 nM (5E-08 M) on a BDD-PdNP electrode modified with 1.0 mM PdCl2 to 5.0 mC in the wet chemical seeding and electrodeposition steps. 0.25 mM PdCl2 to 3.23 mC and 0.25 mM HPtCl6- to 3.23 mC also yielded a sufficient response for low-level H2O2, with LODs around 100 nM (1E-07 M). Overall, this work exemplifies the wide applicability of BDD and achieves sub-μM H2O2 LODs with a non-enzymatic electrode material.

A Novel Fluorescent Probe for the Detection of Hydrogen Peroxide

Hydrogen peroxide (H₂O₂) is one of the important reactive oxygen species (ROS), which is closely related to many pathological and physiological processes in living organisms. Excessive H₂O₂ can lead to cancer, diabetes, cardiovascular diseases, and other diseases, so it is necessary to detect H₂O₂ in living cells. Since this work designed a novel fluorescent probe to detect the concentration of H₂O₂, the H₂O₂ reaction group arylboric acid was attached to the fluorescein 3-Acetyl-7-hydroxycoumarin as a specific recognition group for the selective detection of hydrogen peroxide. The experimental results show that the probe can effectively detect H₂O₂ with high selectivity and measure cellular ROS levels. Therefore, this novel fluorescent probe provides a potential monitoring tool for a variety of diseases caused by H₂O₂ excess.

Synergistic effect of hydrogen bonds and π-π interactions of B(C6F5)3·H2O/amides complex: Application in photoredox catalysis

B(C₆F₅)₃·H₂O has been long recognized as a common Brønsted acid. The lack of X-ray crystal structure of B(C₆F₅)₃·H₂O with other substrates has greatly limited the development of a new catalytic mode. In this work, a complex of B(C₆F₅)₃·H₂O and amide 2-phenyl-3,4-dihydroisoquinolin-1(2H)-one with hydrogen bonds and π-π interactions is characterized by X-ray diffraction. Such noncovalent interactions in solution also exist, as verified by NMR, UV-Vis absorption, and fluorescence emission measurements. Moreover, the mixture of amide 2-phenyl-3,4-dihydroisoquinolin-1(2H)-one and B(C₆F₅)₃·H₂O, instead of other tested Brønsted acids, shows a tailing absorption band in the visible light region (400-450 nm). Based on the photoactive properties of the complex, a photoredox catalysis is developed to construct α-aminoamides under mild conditions.

Paper-Based Humidity Sensors as Promising Flexible Devices: State of the Art: Part 1. General Consideration

In the first part of the review article "General considerations" we give information about conventional flexible platforms and consider the advantages and disadvantages of paper when used in humidity sensors, both as a substrate and as a humidity-sensitive material. This consideration shows that paper, especially nanopaper, is a very promising material for the development of low-cost flexible humidity sensors suitable for a wide range of applications. Various humidity-sensitive materials suitable for use in paper-based sensors are analyzed and the humidity-sensitive characteristics of paper and other humidity-sensitive materials are compared. Various configurations of humidity sensors that can be developed on the basis of paper are considered, and a description of the mechanisms of their operation is given. Next, we discuss the manufacturing features of paper-based humidity sensors. The main attention is paid to the consideration of such problems as patterning and electrode formation. It is shown that printing technologies are the most suitable for mass production of paper-based flexible humidity sensors. At the same time, these technologies are effective both in the formation of a humidity-sensitive layer and in the manufacture of electrodes.

PEDOT Films Doped with Titanyl Oxalate as Chemiresistive and Colorimetric Dual-Mode Sensors for the Detection of Hydrogen Peroxide Vapor

Hydrogen peroxide (H2O2) is commonly used as an oxidizing, bleaching, or antiseptic agent. It is also hazardous at increased concentrations. It is therefore crucial to monitor the presence and concentration of H2O2, particularly in the vapor phase. However, it remains a challenge for many state-of-the-art chemical sensors (e.g., metal oxides) to detect hydrogen peroxide vapor (HPV) because of the interference of moisture in the form of humidity. Moisture, in the form of humidity, is guaranteed to be present in HPV to some extent. To meet this challenge, herein, we report a novel composite material based on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) doped with ammonium titanyl oxalate (ATO). This material can be fabricated as a thin film on electrode substrates for use in chemiresistive sensing of HPV. The adsorbed H2O2 will react with ATO, causing a colorimetric response in the material body. Combining colorimetric and chemiresistive responses resulted in a more reliable dual-function sensing method that improved the selectivity and sensitivity. Moreover, the composite film of PEDOT:PSS-ATO could be coated with a layer of pure PEDOT via in situ electrochemical synthesis. The pure PEDOT layer was hydrophobic, shielding the sensor material underneath from coming into contact with moisture. This was shown to mitigate the interference of humidity when detecting H2O2. A combination of these material properties makes the double-layer composite film, namely PEDOT:PSS-ATO/PEDOT, an ideal sensor platform for the detection of HPV. For example, upon a 9 min exposure to HPV at a concentration of 1.9 ppm, the electrical resistance of the film increased threefold, surpassing the bounds of the safety threshold. Meanwhile, the colorimetric response observed was 2.55 (defined as the color change ratio), a ratio at which the color change could be easily seen by the naked eye and quantified. We expect that this reported dual-mode sensor will find extensive practical applications in the fields of health and security with real-time, onsite monitoring of HPV.

Fluorescent sensor based on solid-phase extraction with negligible depletion: A proof-of-concept study with amines as analytes

This paper describes the development and proof-of-concept testing of an easy-to-use trace analysis technique, namely F-SPE, by coupling fluorescent sensor with solid phase extraction (SPE). F-SPE is a two-step methodology that concentrates an analyte from a liquid sample onto a fluorophore-modified membrane and measures the amount of analyte from the extent the extracted analyte quenches the emission of the fluorophore. By applying the principle of negligible depletion (ND) intrinsic to SPE, the procedure of F-SPE for analyzing a sample can be markedly simplified while maintaining the ability to detect analytes at low limits of detection (LOD). The merits of this approach are demonstrated by impregnating a SPE membrane with a perylene diimide (PDI) fluorophore, N,N'-di(nonyldecyl)-perylene-3,4,9,10-tetracarboxylic diimide (C9/9-PDI), for the low-level detection of organic amines (e.g., aniline) and amine-containing drugs (e.g., Kanamycin). The sensing mechanism is based on the donor-acceptor quenching of PDI by amines, which, when coupled with the concentrative nature of SPE, yields LODs for aniline and Kanamycin of 67 nM (∼6 ppb) and 32 nM (∼16 ppb), respectively.

Detection of Hydrogen Peroxide in Liquid and Vapors Using Titanium(IV)-Based Test Strips and Low-Cost Hardware

Titanium(IV) solutions are known to detect hydrogen peroxide in solutions by a colorimetric method. Xplosafe's XploSens PS commercial titanium(IV)-based peroxide detection test strips are used to detect hydrogen peroxide in liquids. The use of these test strips as gas-phase detectors for peroxides was tested using low-cost hardware. The exposure of these strips to hydrogen peroxide liquid or gas leads to the development of an intense yellow color. For liquids, a digital single-lens reflex camera was used to quantify the color change using standardized solutions containing between 50 and 500 ppm peroxide by mass. Analysis of the images with color separation can provide a more quantitative determination than visual comparison to a color chart. For hydrogen peroxide gas, an inexpensive web camera and a tungsten lamp were used to measure the reflected light intensity as a function of exposure from a test strip held in a custom cell. First-order behavior in the color change with time was observed during the exposure to peroxide vapor over a range of peroxide concentrations from 2 and 30 ppm by volume. For a 1-min measurement, the gas-phase detection limit is estimated to be 1 ppm. A 0.01 ppm detection limit can be obtained with a 1-h exposure time. Titanium(IV)-based peroxide detection test strips are sensitive enough to work as a gas-phase hydrogen peroxide detector.

Rapid and selective on-site detection of triacetone triperoxide based on visual colorimetric method

In this work, a visual colorimetric method for the rapid and selective detection of triacetone triperoxide is reported. This visual colorimetric method is based on the reaction between potassium titanyl oxalate and hydrogen peroxide (H2O2) released from triacetone triperoxide degradation. Potassium titanyl oxalate can selectively react with H2O2 to form peroxo-titanic acid (an orange complex), enabling the colorimetric detection of triacetone triperoxide. Based on the theory that triacetone triperoxide produces hydrogen peroxide under acidic conditions, acid types, acid concentration, response time, visual limit of detection, and reactants ratio are systematically studied simultaneously for this colorimetric method. Under sulfuric acid concentration is 60%, the proposed method can almost detect triacetone triperoxide instantly, and the color of the solution reaches the maximum within 1 min and remains stable with a visual limit of detection as low as 3.0 × 10−5 mol/L. Interference experiments were carried out on other kinds of explosives (hexamethylene triperoxide diamine, trinitrotoluene, etc.). The use of colorimetric card brings great convenience to the rapid, qualitative, and semi-quantitative on-site detection of triacetone triperoxide. Because of its rapidity, high sensitivity, simplicity, and selectivity, the proposed visual colorimetric method can serve as a valuable and promising reference for triacetone triperoxide’s rapid, qualitative on-site detection.

An Enzyme-Based Interdigitated Electrode-Type Biosensor for Detecting Low Concentrations of H2O2 Vapor/Aerosol

This work introduces a novel method for the detection of H2O2 vapor/aerosol of low concentrations, which is mainly applied in the sterilization of equipment in medical industry. Interdigitated electrode (IDE) structures have been fabricated by means of microfabrication techniques. A differential setup of IDEs was prepared, containing an active sensor element (active IDE) and a passive sensor element (passive IDE), where the former was immobilized with an enzymatic membrane of horseradish peroxidase that is selective towards H2O2. Changes in the IDEs’ capacitance values (active sensor element versus passive sensor element) under H2O2 vapor/aerosol atmosphere proved the detection in the concentration range up to 630 ppm with a fast response time (<60 s). The influence of relative humidity was also tested with regard to the sensor signal, showing no cross-sensitivity. The repeatability assessment of the IDE biosensors confirmed their stable capacitive signal in eight subsequent cycles of exposure to H2O2 vapor/aerosol. Room-temperature detection of H2O2 vapor/aerosol with such miniaturized biosensors will allow a future three-dimensional, flexible mapping of aseptic chambers and help to evaluate sterilization assurance in medical industry.

Naked-Eye Detection of Hydrogen Peroxide on Photoluminescent Paper Discs

We have developed a turn-on photoluminescence protocol to detect hydrogen peroxide (H₂O₂) utilizing a supramolecular hydrogel as a sensing platform. Hydrogen peroxide is widely used in formulations, starting from healthcare products to explosives. It is also known to induce deleterious health effects at its irregular physiological concentration and considered as a biomarker in various disease conditions. We designed molecule 2, which releases the Tb³⁺ sensitizer biphenyl-4-carboxylic acid (1) upon unmasking by hydrogen peroxide. This chemistry led us to develop a sensitive photoluminescence assay for H₂O₂ through the 1-induced photoluminescence of terbium (Tb³⁺) in a hydrogel matrix. Paper discs (0.45 cm) were coated with the soft hydrogel to make the sensing process simple and cost-effective. The green luminescence from the paper discs, observed under a UV lamp, allowed naked-eye detection of H₂O₂ in the micromolar level without any sophisticated instrumentation. Image processing software or a plate reader can be used for the accurate quantification of the analyte in micromolar and nanomolar ranges. Several commercial hand sanitizers containing hydrogen peroxide were tested by this method. The results indicated that this low-cost system could be practically adopted, especially in resource-limited areas, to quantify/detect H₂O₂ for quality control purposes or other applications.

Ultrafast fluorescence probe to H2O2 vapor based on organic-inorganic hybrid silica nanoparticles

A kind of organic-inorganic hybrid silica nanoparticles loaded with 1,8-naphthalimide borate ester (NIB@SiO₂) was used to detect trace hydrogen peroxide (H₂O₂) vapor via turn-off mechanism. The detailed studies showed that utilizing silica nanoparticles can improve the adsorption properties and hydrophilicity of the sensing film, accelerate the deboronation reaction between the sensing material and H₂O_2, and then shorten the response time successively, which is always the disturbing challenge for this deboronation-type fluorescent probe to H₂O₂ vapor. The fluorescence of NIB@SiO₂ film was quenched greatly under H₂O₂ saturated vapor within 5 s at room temperature and limit of detection (LOD) was estimated to be 184 ppt, which are among the best reported results. Thus, this study provides an ultrafast and highly sensitive organic-inorganic hybrid fluorescent probe to H₂O₂ vapor, moreover, a new design strategy for promising H₂O₂ fluorescent probe is revealed.

Chromogenic Anticounterfeit and Security Papers: An Easy and Effective Approach

The synthesis and preparation of 12 chromogenic polymers used to build an intelligent label for security paper applications are described. The process involves coating paper sheets with the polymers. Depending on the number of different polymers used in a combinatory way, a maximum of 12¹² combinations is possible, thus creating a matrix that is practically impossible to counterfeit. Currently, most anticounterfeiting proposals for paper-based packaging and documents involve some sort of verification under ultraviolet radiation, and the requirement of additional equipment often relegates the end-user to a passive role. In contrast, in our approach, the combination of sensory polymers in an array gives rise to an invisible label, i.e., an owner cryptographic key, which becomes visible upon scattering a nitrite solution (e.g., spraying or using an impregnated foam roller) over the printed label on the security paper. For this purpose, a monomer containing an aromatic primary amino group and another with an activated aromatic ring are covalently bonded to a polymer with high affinity toward paper, consisting essentially of units of methyl methacrylate and 1-vinyl-2-pyrrolidone. Subsequently, the paper samples are coated with the resulting sensory chromogenic polymer. By spraying, painting, or staining an aqueous acid solution of NaNO₂ (at least 1.20 g/L) and the chromogenic polymers, a well-defined color appears, because of the formation of an azo compound. This process provides users with a quick and facile authentication method without additional equipment and without affecting paper strength.

Measurement of hydrogen peroxide vapor in powders with potassium titanium oxide oxalate loaded cellulose pellets as probes

An image-based method for determining H₂O₂ vapor pressures in powder systems was developed based on cellulose pellets loaded with potassium titanium oxide oxalate (PTO Pellets) as probe particles. Solid titanyl salts change color after exposure to hydrogen peroxide vapor and the quantitative response of PTO pellets to H₂O₂ has been established by comparing reactions with H₂O₂ in liquid and solid states. Analysis of pictures of the color changes of PTO Pellets mixed into powders can be used to monitor the presence of ppm levels of H₂O₂ vapor inside powder systems such as bleach containing dry detergent powders.•H₂O₂ vapor quantification in dry systems with titanyl loaded cellulose particles.•Simple fabrication of H₂O₂ probe particles.•High sensitivity with LOD 0.190 ppm H₂O_{2 .}

NQS-Doped PDMS Solid Sensor: From Water Matrix to Urine Enzymatic Application

The development of in situ analytical devices has gained outstanding scientific interest. A solid sensing membrane composed of 1,2-naphthoquinone-4-sulfonate (NQS) derivatizing reagent embedded into a polymeric polydimethylsiloxane (PDMS) composite was proposed for in situ ammonium (NH₄⁺) and urea (NH₂CONH₂) analysis in water and urine samples, respectively. Satisfactory strategies were also applied for urease-catalyzed hydrolysis of urea, either in solution or glass-supported urease immobilization. Using diffuse reflectance measurements combined with digital image processing of color intensity (RGB coordinates), qualitative and quantitative analyte detection was assessed after the colorimetric reaction took place inside the sensing membrane. A suitable linear relationship was found between the sensor response and analyte concentration, and the results were validated by a thymol-PDMS-based sensor based on the Berthelot reaction. The suggested sensing device offers advantages such as rapidity, versatility, portability, and employment of non-toxic reagents that facilitate in situ analysis in an energy-efficient manner.

Colorimetric sensors and nanoprobes for characterizing antioxidant and energetic substances

The development of analytical techniques for antioxidant compounds is important, because antioxidants that can inactivate reactive species and radicals are health-beneficial compounds, also used in the preservation of food and protection of almost every kind of organic substance from oxidation. Energetic substances include explosives, pyrotechnics, propellants and fuels, and their determination at bulk/trace levels is important for the safety and well-being of modern societies exposed to various security threats. Most of the time, in field/on site detection of these important analytes necessitates the use of colorimetric sensors and probes enabling naked-eye detection, or low-cost and easy-to-use fluorometric sensors. The use of nanosensors brings important advantages to this field of analytical chemistry due to their various physico-chemical advantages of increased surface area, surface plasmon resonance absorption of noble metal nanoparticles, and superior enzyme-mimic catalytic properties. Thus, this critical review focuses on the design strategies for colorimetric sensors and nanoprobes in characterizing antioxidant and energetic substances. In this regard, the main themes and properties in optical sensor design are defined and classified. Nanomaterial-based optical sensors/probes are discussed with respect to their mechanisms of operation, namely formation and growth of noble metal nanoparticles, their aggregation and disaggregation, displacement of active constituents by complexation or electrostatic interaction, miscellaneous mechanisms, and the choice of metallic oxide nanoparticles taking part in such formulations.

Disposable and Low-Cost Colorimetric Sensors for Environmental Analysis

Environmental contamination affects human health and reduces the quality of life. Therefore, the monitoring of water and air quality is important, ensuring that all areas are acquiescent with the current legislation. Colorimetric sensors deliver quick, naked-eye detection, low-cost, and adequate determination of environmental analytes. In particular, disposable sensors are cheap and easy-to-use devices for single-shot measurements. Due to increasing requests for in situ analysis or resource-limited zones, disposable sensors’ development has increased. This review provides a brief insight into low-cost and disposable colorimetric sensors currently used for environmental analysis. The advantages and disadvantages of different colorimetric devices for environmental analysis are discussed.

Detection of hydrogen peroxide using dioxazaborocanes: elucidation of the sensing mechanism at the molecular level by NMR and XPS measurements

The H₂O₂vapour cleaves the N–B bond and inhibits the fluorescence of the dixazaborocane.

Combined calorimetric gas- and spore-based biosensor array for online monitoring and sterility assurance of gaseous hydrogen peroxide in aseptic filling machines

A combined calorimetric gas- and spore-based biosensor array is presented in this work to monitor and evaluate the sterilization efficacy of gaseous hydrogen peroxide in aseptic filling machines. H₂O₂ has been successfully measured under industrial conditions. Furthermore, the effect of H₂O₂ on three different spore strains , namely Bacillus atrophaeus, Bacillus subtilis and Geobacillus stearothermophilus, has been investigated by means of SEM, AFM and impedimetric measurements. In addition, the sterilization efficacy of a spore-based biosensor and the functioning principle are addressed and discussed: the sensor array is convenient to be used in aseptic food industry to guarantee sterile packages.

Titanium dioxide nanoparticles-based colorimetric sensors for determination of hydrogen peroxide and triacetone triperoxide (TATP)

Due to its relatively simple preparation and readily available precursors, determination of triacetone triperoxide (TATP) by portable devices has become important. In this work, two different titanium dioxide nanoparticles (TiO₂NPs)-based colorimetric sensors based on complex formation on the solid surface were developed for determination of H₂O₂ and TATP. The first sensor, (3-aminopropyl)triethoxysilane (APTES) modified-TiO₂NPs-based paper sensor (APTES@TiO₂NPs), exploits peroxo-titanate binary complex formation between APTES@TiO₂NPs and H₂O₂ on chromatographic paper. The second sensor, 4-(2-pyridylazo)-resorcinol-modified-TiO₂NPs-based solid sensor (PAR@TiO₂NPs), relies on the formation of a ternary complex between Ti(IV), PAR and H₂O₂. The developed sensors were also applied to TATP determination after acidic hydrolysis of samples to H₂O₂. The limits of detection (LODs) of APTES@TiO₂NPs-based paper sensor were 3.14 × 10^-4 and 5.13 × 10^-4 mol L^-1 for H₂O₂ and TATP, respectively, whereas the LODs of PAR@TiO₂NPs solid sensor were 6.06 × 10^-7 and 3.54 × 10^-7 mol L^-1 for H₂O₂ and TATP, respectively. Possible interferences of common soil ions, passenger belongings used as camouflage materials during public transport (e.g., detergent, sweetener, acetylsalicylic acid and paracetamol-caffeine based analgesic drugs) and of other explosives were examined. The developed methods were statistically validated using t- and F- tests against the titanyl sulfate (TiOSO₄) colorimetric literature method.

Fast, sensitive, selective and reversible fluorescence monitoring of TATP in a vapor phase

The development of sensors for the detection of triacetone triperoxide (TATP) has attracted great attention. Here, we constructed a low-cost, portable, reusable, visible paper-based fluorescent sensor for the sensitive detection of TATP via vapor sampling. Under optimized conditions, the fluorescent film showed a high sensitivity to TATP with a detection limit of lower than 0.5 μg mL-1 in air. The linear range of the response is from 0.5 to 8.0 μg mL-1. In addition, the paper-based sensor exhibited high selectivity to TATP. The presence of potential interferents showed little effect on sensing. Moreover, sensing is fully reversible. Fortunately, the test can also be conducted in a visualized way.

An Adenosine Triphosphate-Responsive Autocatalytic Fenton Nanoparticle for Tumor Ablation with Self-Supplied H2O2 and Acceleration of Fe(III)/Fe(II) Conversion

Chemodynamic therapy (CDT) can efficiently destroy tumor cells via Fenton reaction in the presence of H₂O₂ and a robust catalyst. However, it has faced severe challenges including the limited amounts of H₂O₂ and inefficiency of catalysts. Here, an adenosine triphosphate (ATP)-responsive autocatalytic Fenton nanosystem (GOx@ZIF@MPN), incorporated with glucose oxidase (GOx) in zeolitic imidazolate framework (ZIF) and then coated with metal polyphenol network (MPN), was designed and synthesized for tumor ablation with self-supplied H₂O₂ and TA-mediated acceleration of Fe(III)/Fe(II) conversion. In the ATP-overexpressed tumor cells, the outer shell MPN of GOx@ZIF@MPN was degraded into Fe(III) and tannic acid (TA) and the internal GOx was exposed. Then, GOx reacted with the endogenous glucose to produce plenty of H₂O₂, and TA reduced Fe(III) to Fe(II), which is a much more vigorous catalyst for the Fenton reaction. Subsequently, self-produced H₂O₂ was catalyzed by Fe(II) to generate highly toxic hydroxyl radical (•OH) and Fe(III). The produced Fe(III) with low catalytic activity was quickly reduced to reactive Fe(II) mediated by TA, forming an accelerated Fe(III)/Fe(II) conversion to guarantee efficient Fenton reaction-mediated CDT. This autocatalytic Fenton nanosystem might provide a good paradigm for effective tumor treatment.

Colorimetric sensors for rapid detection of various analytes

Sensor technology for the rapid detection of the analytes with high sensitivity and selectivity has several challenges. Despite the challenges, colorimetric sensors have been widely accepted for its high sensitive and selective response towards various analytes. In this review, colorimetric sensors for the detection of biomolecules like protein, DNA, pathogen and chemical compounds like heavy metal ions, toxic gases and organic compounds have been elaborately discussed. The visible sensing mechanism based on Surface Plasmon Resonance (SPR) using metal nanoparticles like Au, Ag, thin film interference using SiO₂ and colorimetric array-based technique have been highlighted. The optical property of metal nanoparticles enables a visual color change during its interaction with the analytes owing to the dispersion and aggregation of nanoparticles. Recently, colorimetric changes using silica substrate for detection of protein and small molecules by thin film interference as a visible sensing mechanism has been developed without the usage of fluorescent or radioisotopes labels. Multilayer of biomaterials were used as a platform where reflection and interference of scattering light occur due to which color change happens leading to rapid sensing. Colorimetric array-based technique for the detection of organic compounds using chemoresponsive dyes has also been focused wherein the interaction of the analytes with the substrate coated with chemoresponsive dyes gives colorimetric change.

Electrochemical hydrogen peroxide sensor based on carbon supported Cu@Pt core-shell nanoparticles

The Cu@Pt/C nanocomposites have been synthesized via two-step reduction method. Electrochemical observations showed that the Cu@Pt/C had better electrocatalytic activity for the reduction of hydrogen peroxide than Pt/C, with a wide linear range between 0.50μM and 32.56mM, a high sensitivity of 351.3μAmM^-1cm^-2, and a low detection limit of 0.15μM (signal/noise=3). Furthermore, the sensor based on Cu@Pt/C has potential applications due to its excellent long-time stability, good reproducibility and acceptable selectivity.

Design, synthesis and properties of a reactive chromophoric/fluorometric probe for hydrogen peroxide detection

A succinct chromophoric/fluorometric probe, AVPM, for sensitive and selective H₂O₂detection.

Facile fabrication of paper-based analytical devices for rapid and highly selective colorimetric detection of cesium in environmental samples

Cesium (Cs), a radioactive contaminant of the ecosystem, causes a major risk to human health and environments. This chemo-indicator is designed to exhibit a powerful detection capability featuring high selectivity and sensitivity to inactive Cs.

New Functionalities for Paper-Based Sensors Lead to Simplified User Operation, Lower Limits of Detection, and New Applications

In the last decade, paper analytical devices (PADs) have evolved into sophisticated yet simple sensors with biological and environmental applications in the developed and developing world. The focus of this review is the technological improvements that have over the past five years increased the applicability of PADs to real-world problems. Specifically, this review reports on advances in sample processing, fluid flow control, signal amplification, and component integration. Throughout, we have sought to emphasize advances that retain the main virtues of PADs: low cost, portability, and simplicity.

A highly facile and selective Chemo-Paper-Sensor (CPS) for detection of strontium

Chemosensors have attracted increasing attention for their usefulness on-site detection and monitoring. In this study, we elucidated a novel, facile, and highly selective Chemo-Paper-Sensor (CPS) for detection and monitoring of strontium (Sr(2+)) ions, which means a potent colorimetric sensor based on a Chrysoidine G (CG)-coated paper strip. The CPS for highly selective colorimetric detection of strontium ion was handily analyzed to determine the red-green-blue (RGB) value using portable devices such as desktop digital scanner and mobile phone camera, quantitatively. Interestingly, an orange to dark orange color transition was observed when the aqueous and solid paper colorimetric sensor was introduced to Sr(2+) ion, respectively. It was demonstrated that the value of the signal has a linear relationship with concentrations of the strontium in the 500 ppm to 100 ppb range with a detection limit of 200 ppb. We believe that a newly developed Chemo-Paper-Sensor will be useful in a wide range of sensing applications.