Novel Self-Assembly Route Assisted Ultra-Fast Trace Volatile Organic Compounds Gas Sensing Based on Three-Dimensional Opal Microspheres Composites for Diabetes Diagnosis

Foldable and Wearable Fabric Ammonia Sensor Based on a Polyaniline/Polyacrylonitrile Nanofiber for Smart Home Applications

Flexible gas sensors are gaining increasing recognition for their potential applications in the realm of electronic skin and smart textiles. However, owing to the insufficient adhesion property between the organic flexible substrate, metal electrodes, and sensing film, traditional flexible sensors often suffer from terrible durability under intense bending or folding conditions. In this study, a flexible fabric ammonia (NH3) sensor composed of an electrospun preoxidized polyacrylonitrile (PAN) fiber-based flexible substrate and an in situ self-assembled polyaniline (PANI) sensing film/electrode was rationally designed. Owing to the favorable adhesion capability on the polymer substrate, excellent conductivity, and outstanding sensitivity to NH3, the in situ self-assembled PANI film endowed the sensor with exceptional flexibility. Meanwhile, the low elastic modulus of the fabric sensor guarantees its comfortable wearability. Apart from the superior sensing performances toward 2-50 ppm of NH3, the fabricated fabric sensor revealed little response fluctuation (4%) to 10 ppm of NH3 under the bending angles from 0° to 180° and maintained negligible response changes (3.2%) under 1000 cycles of bending treatment with a bending angle of 120°. The designed fabric gas sensor is further developed into wearable devices for validating its versatility and reliability in multiscenario smart home applications. The design strategy presented here not only addresses the challenges associated with the durability of flexible sensors but also paves the way for the exploration of next-generation flexible gas sensors tailored across various wearable applications.

Nitrogen-Doped Carbon Quantum Dots Activated Dandelion-Like Hierarchical WO3 for Highly Sensitive and Selective MEMS Sensors in Diabetes Detection

High sensitivity, low concentration, and excellent selectivity are pronounced primary challenges for semiconductor gas sensors to monitor acetone from exhaled breath. In this study, nitrogen-doped carbon quantum dots (N-CQDs) with high reactivity were used to activate dandelion-like hierarchical tungsten oxide (WO3) microspheres to construct an efficient and stable acetone gas sensor. Benefiting from the synergistic effect of both the abundant active sites provided by the unique dandelion-like hierarchical structure and the high reaction potential generated by the sensitization of the N-CQDs, the resulting 16 wt % N-CQDs/WO3 sensor shows an ultrahigh response value (Ra/Rg = 74@1 ppm acetone), low detection limit (0.05 ppm), outstanding selectivity, and reliable stability to acetone at the optimum working temperature of 210 °C. Noteworthy that the N-CQDs facilitate the carrier migration and intensify the reaction between acetone and WO3 during the sensing process. Considering the above advantages, N-CQDs as a sensitizer to achieve excellent gas-sensitive properties of WO3 are a promising new strategy for achieving accurate acetone detection in real time and facilitating the development of portable human-exhaled gas sensors.

Imparting Chemiresistor with Humidity-Independent Sensitivity toward Trace-Level Formaldehyde via Substitutional Doping Platinum Single Atom

The modification of metal oxides with noble metals is one of the most effective means of improving gas-sensing performance of chemiresistors, but it is often accompanied by unintended side effects such as sensor resistance increases up to unmeasurable levels. Herein, a carbonization-oxidation method is demonstrated using ultrasonic spray pyrolysis technique to realize platinum (Pt) single atom (SA) substitutional doping into SnO2 (named PtSA-SnO2). The substitutional doping strategy can obviously enhance gas-sensing properties, and meanwhile decrease sensor resistance by two orders of magnitude (decreased from ≈850 to ≈2 MΩ), which are attributed to the tuning of band gap and fermi-level position, efficient single atom catalysis, and the raising of adsorption capability of formaldehyde, as validated by the state-of-the-art characterizations, such as spherical aberration-corrected scanning transmission electron microscopy (Cs-corrected STEM), in situ diffuse reflectance infrared Fourier transformed spectra (in situ DRIFT), CO temperature-programmed reduction (CO-TPR), and theoretical calculations. As a proof of concept, the developed PtSA-SnO2 sensor shows humidity-independent (30-70% relative humidity) gas-sensing performance in the selective detection of formaldehyde with high response, distinguishable selectivity (8< Sformaldehyde/Sinterferant <14), and ultra-low detection limit (10 ppb). This work presents a generalized and facile method to design high-performance metal oxides for chemical sensing of volatile organic compounds (VOCs).

Triboelectric Nanogenerators for Preventive Health Monitoring

With the improvement in life quality, the increased focus on health has expedited the rapid development of portable preventative-health-monitoring devices. As one of the most attractive sensing technologies, triboelectric nanogenerators (TENGs) are playing a more and more important role in wearable electronics, machinery condition monitoring, and Internet of Things (IoT) sensors. TENGs possess many advantages, such as ease of fabrication, cost-effectiveness, flexibility, material-selection variety, and the ability to collect low-frequency motion, offering a novel way to achieve health monitoring for human beings in various aspects. In this short review, we initially present the working modes of TENGs based on their applications in health monitoring. Subsequently, the applications of TENG-based preventive health monitoring are demonstrated for different abnormal conditions of human beings, including fall-down detection, respiration monitoring, fatigue monitoring, and arterial pulse monitoring for cardiovascular disease. Finally, the discussion summarizes the current limitations and future perspectives. This short review encapsulates the latest and most influential works on preventive health monitoring utilizing the triboelectric effect for human beings and provides hints and evidence for future research trends.

Artificial Neural Processing-Driven Bioelectronic Nose for the Diagnosis of Diabetes and Its Complications

Diabetes and its complications affect the younger population and are associated with a high mortality rate; however, early diagnosis can contribute to the selection of appropriate treatment regimens that can reduce mortality. Although diabetes diagnosis via exhaled breath has great potential for early diagnosis, research on such diagnosis is restricted to disease detection, requiring in-depth examination to diagnose and classify diseases and their complications. This study demonstrates the use of an artificial neural processing-based bioelectronic nose to accurately diagnose diabetes and classify diabetic types (type I and II) and their complications, such as heart disease. Specifically, an M13 phage-based electronic nose (e-nose) is used to explore the features of subjects with diabetes at various levels of cellular and organismal organization (cells, liver organoids, and mice). Exhaled breath samples are collected during culturing and exposed to the phage-based e-nose. Compared with cells, liver organoids cultured under conditions mimicking a diabetic environment display properties that closely resemble the characteristics of diabetic mice. Using neural pattern separation, the M13 phage-based e-nose achieves a classification success rate of over 86% for four conditions in mice, namely, type 1 diabetes, type 2 diabetes, diabetic cardiomyopathy, and cardiomyopathy.

Challenges and Opportunities of Chemiresistors Based on Microelectromechanical Systems for Chemical Olfaction

Microelectromechanical-system (MEMS)-based semiconductor gas sensors are considered one of the fastest-growing, interdisciplinary high technologies during the post-Moore era. Modern advancements within this arena include wearable electronics, Internet of Things, and artificial brain-inspired intelligence, among other modalities, thus bringing opportunities to drive MEMS-based gas sensors with higher performance, lower costs, and wider applicability. However, the high demand for miniature and micropower sensors with unified processes on a single chip imposes great challenges. This review focuses on recent developments and pitfalls in MEMS-based micro- and nanoscale gas sensors and details future trends. We also cover the background of the topic, seminal efforts, current applications and challenges, and opportunities for next-generation systems.

Metal Oxide Chemiresistors: A Structural and Functional Comparison between Nanowires and Nanoparticles

Metal oxide nanowires have become popular materials in gas sensing, and more generally in the field of electronic and optoelectronic devices. This is thanks to their unique structural and morphological features, namely their single-crystalline structure, their nano-sized diameter and their highly anisotropic shape, i.e., a large length-to-diameter aspect ratio. About twenty years have passed since the first publication proposing their suitability for gas sensors, and a rapidly increasing number of papers addressing the understanding and the exploitation of these materials in chemosensing have been published. Considering the remarkable progress achieved so far, the present paper aims at reviewing these results, emphasizing the comparison with state-of-the-art nanoparticle-based materials. The goal is to highlight, wherever possible, how results may be related to the particular features of one or the other morphology, what is effectively unique to nanowires and what can be obtained by both. Transduction, receptor and utility-factor functions, doping, and the addition of inorganic and organic coatings will be discussed on the basis of the structural and morphological features that have stimulated this field of research since its early stage.

Diversified applications of self-assembled nanocluster delivery systems- A state-of-the- art review

BACKGROUND

Self-assembled nanoclusters arrange the components into an organized structure for the nanoparticulate system and also in the transportation of cellular elements for the fabrication of microelectronic devices. Nanoclusters reduce transcytosis and increase endocytosis in intestinal mucin to strengthen the retrograde pathway that helped in the delivery of actives to the Golgi apparatus.

OBJECTIVES

This review article focuses on the self-assembled nanoclusters for cellular transportation, applications of self-assembled structures in the delivery of essential elements like the use of a peptide in targeted and stimuli-responsive drug delivery systems, self-assembly of tocopherol nanoclusters that promotes vitamin E delivery across the endothelial barrier. Methods Current innovation in the self-assembly of peptides includes the formation of nanostructures like vesicles, fibers, and rod-coil in the applications of wound healing, tissue engineering, treatment of atherosclerosis, in sensing heavy metals from biological and environmental samples and advanced drug delivery.

RESULTS

Self-assembled biodegradable nanoclusters are used as biomimetic structures for synergistic effect. Improvement in the methods of preparation like the addition of a copolymer is used for temperature-triggered drug release nanoclusters.

CONCLUSION

Green synthesis of nanoclusters, nanocluster-based biosensor and artificial intelligence are the future concept in the manufacturing and the prevention of toxicity in humans.

Emerging Theranostic Nanomaterials in Diabetes and Its Complications

Diabetes mellitus (DM) refers to a group of metabolic disorders that are characterized by hyperglycemia. Oral subcutaneously administered antidiabetic drugs such as insulin, glipalamide, and metformin can temporarily balance blood sugar levels, however, long-term administration of these therapies is associated with undesirable side effects on the kidney and liver. In addition, due to overproduction of reactive oxygen species and hyperglycemia-induced macrovascular system damage, diabetics have an increased risk of complications. Fortunately, recent advances in nanomaterials have provided new opportunities for diabetes therapy and diagnosis. This review provides a panoramic overview of the current nanomaterials for the detection of diabetic biomarkers and diabetes treatment. Apart from diabetic sensing mechanisms and antidiabetic activities, the applications of these bioengineered nanoparticles for preventing several diabetic complications are elucidated. This review provides an overall perspective in this field, including current challenges and future trends, which may be helpful in informing the development of novel nanomaterials with new functions and properties for diabetes diagnosis and therapy.

Self-Powered Respiration Monitoring Enabled By a Triboelectric Nanogenerator

In mammals, physiological respiration involves respiratory cycles of inhaled and exhaled breaths, which has traditionally been an underutilized resource potentially encompassing a wealth of physiologically relevant information as well as clues to potential diseases. Recently, triboelectric nanogenerators (TENGs) have been widely adopted for self-powered respiration monitoring owing to their compelling features, such as decent biocompatibility, wearing comfort, low-cost, and high sensitivity to respiration activities in the aspect of low frequency and slight amplitude body motions. Physiological respiration behaviors and exhaled chemical regents can be precisely and continuously monitored by TENG-based respiration sensors for personalized health care. This article presents an overview of TENG enabled self-powered respiration monitoring, with a focus on the working principle, sensing materials, functional structures, and related applications in both physical respiration motion detection and chemical breath analysis. Concepts and approaches for acquisition of physical information associated with respiratory rate and depth are covered in the first part. Then the sensing mechanism, theoretical modeling, and applications related to detection of chemicals released from breathing gases are systemically summarized. Finally, the opportunities and challenges of triboelectric effect enabled self-powered respiration monitoring are comprehensively discussed and criticized.

Morphological Effects in SnO2 Chemiresistors for Ethanol Detection: A Review in Terms of Central Performances and Outliers

SnO₂ is one of the most studied materials in gas sensing and is often used as a benchmark for other metal oxide-based gas sensors. To optimize its structural and functional features, the fine tuning of the morphology in nanoparticles, nanowires, nanosheets and their eventual hierarchical organization has become an active field of research. In this paper, the different SnO₂ morphologies reported in literature in the last five years are systematically compared in terms of response amplitude through a statistical approach. To have a dataset as homogeneous as possible, which is necessary for a reliable comparison, the analysis is carried out on sensors based on pure SnO₂, focusing on ethanol detection in a dry air background as case study. Concerning the central performances of each morphology, results indicate that none clearly outperform the others, while a few individual materials emerge as remarkable outliers with respect to the whole dataset. The observed central performances and outliers may represent a suitable reference for future research activities in the field.

A Nanostructured Microfluidic Artificial Olfaction for Organic Vapors Recognition

Selective and sensitive detection of volatile organic compounds (VOCs) is of great importance in applications involving monitoring of hazardous chemicals or non-invasive diagnosis. Here, polymethyl methacrylate nanoparticles with acetone recognition sites are synthesized and integrated into a 3D-printed microfluidic platform to enhance the selectivity of the device. The proposed microfluidic-based olfaction system includes two parylene C-coated microchannels, with or without polymer nanoparticles. The two channels are exposed to 200, 400, 800, 2000, and 4000 ppm of VOCs (methanol, ethanol, acetone, acetonitrile, butanone, and toluene), and sensor responses are compared using a 2D feature extraction method. Compared to current microfluidic-based olfaction systems, responses observed between coated and uncoated channels showed an increased recognition capability among VOCs (especially with respect to acetone), indicating the potential of this approach to increase and fine-tune the selectivity of microfluidic gas sensors.

Synthesis of Nano-Praseodymium Oxide for Cataluminescence Sensing of Acetophenone in Exhaled Breath

In this work, we successfully developed a novel and sensitive gas sensor for the determination of trace acetophenone based on its cataluminescence (CTL) emission on the surface of nano-praseodymium oxide (nano-Pr₆O₁₁). The effects of working conditions such as temperature, flow rate, and detecting wavelength on the CTL sensing were investigated in detail. Under the optimized conditions, the sensor exhibited linear response to the acetophenone in the range of 15-280 mg/m³ (2.8-52 ppm), with a correlation coefficient (R²) of 0.9968 and a limit of detection (S/N = 3) of 4 mg/m³ (0.7 ppm). The selectivity of the sensor was also investigated, no or weak response to other compounds, such as alcohols (methanol, ethanol, n-propanol, iso-propanol, n-butanol), aldehyde (formaldehyde and acetaldehyde), benzenes (toluene, o-xylene, m-xylene, p-xylene), n-pentane, ethyl acetate, ammonia, carbon monoxide, carbon dioxide. Finally, the present sensor was applied to the determination of acetophenone in human exhaled breath samples. The results showed that the sensor has promising application in clinical breath analysis.

Graphene quantum dot-functionalized three-dimensional ordered mesoporous ZnO for acetone detection toward diagnosis of diabetes

The development of a high-performance semiconductor oxide sensor for the accurate detection of trace disease biomarkers in exhaled breath is still a challenge that urgently needs to be addressed. Here, we proposed a self-assembly strategy and spin-coating process to create a graphene quantum dot (GQD)-functionalized three-dimensional ordered macroporous (3DOM) ZnO structure. The strong synergistic effect and the p-n heterojunction between the p-type GQDs and n-type ZnO effectively enlarged the resistance variation due to the change in oxygen adsorption. The specific 3DOM structure induced a hierarchical pore size (286 nm in macroscale and 26 nm in mesoscale) and 3D interconnection, which guaranteed high gas accessibility and fast carrier transportation. As a result, the GQD-modified 3DOM ZnO sensor exhibited a remarkably high response (Rair/Rgas = 15.2 for 1 ppm acetone), rapid response/recovery time (9/16 s), extremely low theoretical detection limit (8.7 ppb), and good selectivity towards acetone against other interfering gases. In particular, the proposed sensor could accurately distinguish trace acetone in the simulated breath of diabetic patients. These results demonstrate a high potential for the feasibility of the GQD-modified 3DOM SMO structure as a new sensing material for the possibility of noninvasive real-time diagnosis of diabetes.

Realizing the Control of Electronic Energy Level Structure and Gas-Sensing Selectivity over Heteroatom-Doped In2O3 Spheres with an Inverse Opal Microstructure

Understanding the effect of substitutional doping on gas-sensing performances is essential for designing high-activity sensing nanomaterials. Herein, formaldehyde sensors based on gallium-doped In₂O₃ inverse opal (IO-(Ga _xIn_{1- x})₂O₃) microspheres were purposefully prepared by a simple ultrasonic spray pyrolysis method combined with self-assembled sulfonated polystyrene sphere templates. The well-aligned inverse opal structure, with three different-sized pores, plays the dual role of accelerating the diffusion of gas molecules and providing more active sites. The Ga substitutional doping can alter the electronic energy level structure of (Ga _xIn_{1- x})₂O₃, leading to the elevation of the Fermi level and the modulation of the band gap close to a suitable value (3.90 eV), hence, effectively optimizing the oxidative catalytic activity for preferential CH₂O oxidation and increasing the amount of adsorbed oxygen. More importantly, the gas selectivity could be controlled by varying the energy level of adsorbed oxygen. Accordingly, the IO-(Ga_0.2In_0.8)₂O₃ microsphere sensor showed a high response toward formaldehyde with fast response and recovery speeds, and ultralow detection limit (50 ppb). Our findings finally offer implications for designing Fermi level-tailorable semiconductor nanomaterials for the control of selectivity and monitoring indoor air pollutants.

Understanding the noble metal modifying effect on In2O3 nanowires: highly sensitive and selective gas sensors for potential early screening of multiple diseases

Sensor arrays consisting of In₂O₃ NWs loaded with different NMNPs can accurately distinguish different trace VOC biomarkers in simulated exhaled breath.

Tailoring energy level and surface basicity of metal oxide semiconductors by rare-earth incorporation for high-performance formaldehyde detection

The elevated Fermi level and increased surface basicity of 5Y-In₂O₃ led to the improvement of response and selectivity towards formaldehyde.