Innovative Nanosensor for Disease Diagnosis

Biomarker-triggered, spatiotemporal controlled DNA nanodevice simultaneous assembly and disassembly

Despite many advances in the use of DNA nanodevices as assembly or disassembly modules to build various complex structures, the simultaneous assembly and disassembly of DNA structures in living cells remains a challenge. In this study, we present a modular engineering approach for assembling and disassembling DNA nanodevices in response to endogenous biomarkers. As a result of pairwise prehybridization of original DNA strands, the DNA nanodevice is initially inert. In an effort to bind one of the paired strands and release its complement, nucleolin competes. Assembly of the DNA nanodevice is initiated when the released complement binds to it, and disassembly is initiated when APE1 shears the assembled binding site of the DNA nanodevice. Spatial-temporal logic control is achieved through our approach during the assembly and disassembly of DNA nanodevices. Furthermore, by means of this assembly and disassembly procedure, the sequential detection and imaging of two tumor markers can be achieved, thereby effectively reducing false-positive signal results and accelerating the detection time. This study emphasizes the simultaneous assembly and disassembly of DNA nanodevices controlled by biomarkers in a simple and versatile manner; it has the potential to expand the application scope of DNA nanotechnology and offers an idea for the implementation of precision medicine testing.

Dynamic Interchain Motion in 1D Tetrathiafulvalene-Based Coordination Polymers for Highly Sensitive Molecular Recognition

The application of electrically conductive 1D coordination polymers (1D CPs) in nanoelectronic molecular recognition is theoretically promising yet rarely explored due to the challenges in their synthesis and optimization of electrical properties. In this regard, two tetrathiafulvalene-based 1D CPs, namely [Co(m-H2TTFTB)(DMF)2(H2O)]n (Co-m-TTFTB), and {[Ni(m-H2TTFTB)(CH3CH2OH)1.5(H2O)1.5]·(H2O)0.5}n (Ni-m-TTFTB) are successfully constructed. The shorter S···S contacts between the [M(solvent)3(m-H2TTFTB)]n chains contribute to a significant improvement in their electrical conductivities. The powder X-ray diffraction (PXRD) under different organic solvents reveals the flexible and dynamic structural characteristic of M-m-TTFTB, which, combined with the 1D morphology, lead to their excellent performance for sensitive detection of volatile organic compounds. Co-m-TTFTB achieves a limit of detection for ethanol vapor down to 0.5 ppm, which is superior to the state-of-the-art chemiresistive sensors based on metal-organic frameworks or organic polymers at room temperature. In situ diffuse reflectance infrared Fourier transform spectroscopy, PXRD measurements and density functional theory calculations reveal the molecular insertion sensing mechanism and the corresponding structure-function relationship. This work expands the applicable scenario of 1D CPs and opens a new realm of 1D CP-based nanoelectronic sensors for highly sensitive room temperature gas detection.

Emerging trends in metal oxide-based electronic noses for healthcare applications: a review

An electronic nose (E-nose) is a technology fundamentally inspired by the human nose, designed to detect, recognize, and differentiate specific odors or volatile components in complex and chaotic environments. Comprising an array of sensors with meticulously designed nanostructured architectures, E-noses translate the chemical information captured by these sensors into useful metrics using complex pattern recognition algorithms. E-noses can significantly enhance the quality of life by offering preventive point-of-care devices for medical diagnostics through breath analysis, and by monitoring and tracking hazardous and toxic gases in the environment. They are increasingly being used in defense and surveillance, medical diagnostics, agriculture, environmental monitoring, and product validation and authentication. The major challenge in developing a reliable E-nose involves miniaturization and low power consumption. Various sensing materials are employed to address these issues. This review presents the key advancements over the last decade in E-nose technology, specifically focusing on chemiresistive metal oxide sensing materials. It discusses their sensing mechanisms, integration into portable E-noses, and various data analysis techniques. Additionally, we review the primary metal oxide-based E-noses for disease detection through breath analysis. Finally, we address the major challenges and issues in developing and implementing a portable metal oxide-based E-nose.

High-Performance Room Temperature Ammonia Sensors Based on Pure Organic Molecules Featuring B-N Covalent Bond

Exploring organic semiconductor gas sensors with high sensitivity and selectivity is crucial for the development of sensor technology. Herein, for the first time, a promising chemiresistive organic polymer P-BNT based on a novel π-conjugated triarylboron building block is reported, showcasing an excellent responsivity over 30 000 (Ra/Rg) against 40 ppm of NH3, which is ≈3300 times higher than that of its B-N organic small molecule BN-H. More importantly, a molecular induction strategy to weaken the bond dissociation energy between polymer and NH3 caused by strong acid-base interaction is further executed to optimize the response and recovery time. As a result, the BN-H/P-BNT system with rapid response and recovery times can still exhibit a high responsivity of 718, which is among the highest reported NH3 chemiresistive sensors. Supported by in situ FTIR spectroscopy and theoretical calculations, it is revealed that the N-H fractions in BN-H small molecule promoted the charge distribution on phenyl groups, which increases charge delocalization and is more conducive to gas adsorption in such molecular systems. Notably, these distinctive small molecules also promoted charge transfer and enhanced electron concentration of the P-BNT sensing polymer, thus achieving superior B-N-containing organic molecules with excellent sensing performance.

Encapsulation of copper phenanthroline within horse spleen apoferritin: characterisation, cytotoxic activity and ability to retain temozolomide

Protein capsules are promising drug delivery vehicles for cancer research therapies. Apoferritin (AFt) is a self-assembling 12 nm diameter hollow nanocage with many desirable features for drug delivery, however, control of drug retention inside the protein cage remains challenging. Here we report the encapsulation of copper(ii)-1,10-phenanthroline (Cu(phen)) within the horse spleen AFt (HSAFt) nanocage, by diffusion of the metal through the pores between the protein subunits. Transmission electron microscopy revealed the formation of organised copper adducts inside HSAFt, without affecting protein integrity. These structures proved stable during storage (>4 months at -20 °C). Exposure to physiologically relevant conditions (37 °C) showed some selectivity in cargo release after 24 h at pH 5.5, relevant to the internalisation of AFt within the endosome (60% release), compared to pH 7.4, relevant to the bloodstream (40% release). Co-encapsulation of temozolomide, a prodrug used to treat glioblastoma multiforme, and Cu(phen) enabled entrapment of an average of 339 TMZ molecules per cage. In vitro results from MTT and clonogenic assays identified cytotoxic activity of the Cu(phen), HSAFt-Cu(phen) and HSAFt-Cu(phen)-TMZ adducts against colorectal cancer cells (HCT-116) and glioblastoma cells (U373V, U373M). However, the presence of the metal also contributed to more potent activity toward healthy MRC5 fibroblasts, a result that requires further investigation to assess the clinical viability of this system.

A Versatile Synthesis Platform Based on Polymer Cubosomes for a Library of Highly Ordered Nanoporous Metal Oxides Particles

Polymer cubosomes (PCs) have well-defined inverse bicontinuous cubic mesophases formed by amphiphilic block copolymer bilayers. The open hydrophilic channels, large periods, and robust physical properties of PCs are advantageous to many host-guest interactions and yet not fully exploited, especially in the fields of functional nanomaterials. Here, the self-assembly of poly(ethylene oxide)-block-polystyrene block copolymers is systematically investigated and a series of robust PCs is developed via a cosolvent method. Ordered nanoporous metal oxide particles are obtained by selectively filling the hydrophilic channels of PCs via an impregnation strategy, followed by a two-step thermal treatment. Based on this versatile PC platform, the general synthesis of a library of ordered porous particles with different pore structures3 ¯ $\bar{3}$ 3 ¯ $\bar{3}$ , tunable large pore size (18-78 nm), high specific surface areas (up to 123.3 m2 g-1 for WO3) and diverse framework compositions, such as transition and non-transition metal oxides, rare earth chloride oxides, perovskite, pyrochlore, and high-entropy metal oxides is demonstrated. As typical materials obtained via this method, ordered porous WO3 particles have the advantages of open continuous structure and semiconducting properties, thus showing superior gas sensing performances toward hydrogen sulfide.

Ceria-Based Nanozymes in Point-of-Care Diagnosis: An Emerging Futuristic Approach for Biosensing

In recent years, there has been a notable increase in interest surrounding nanozymes due to their ability to imitate the functions and address the limitations of natural enzymes. The scientific community has been greatly intrigued by the study of nanoceria, primarily because of their distinctive physicochemical characteristics, which include a variety of enzyme-like activities, affordability, exceptional stability, and the ability to easily modify their surfaces. Consequently, nanoceria have found extensive use in various biosensing applications. However, the impact of its redox activity on the enzymatic catalytic mechanism remains a subject of debate, as conflicting findings in the literature have presented both pro-oxidant and antioxidant effects. Herein, we creatively propose a seesaw model to clarify the regulatory mechanism on redox balance and survey possible mechanisms of multienzyme mimetic properties of nanoceria. In addition, this review aims to showcase the latest advancements in this field by systematically discussing over 180 research articles elucidating the significance of ceria-based nanozymes in enhancing, downsizing, and enhancing the efficacy of point-of-care (POC) diagnostics. These advancements align with the ASSURED criteria established by the World Health Organization (WHO). Furthermore, this review also examines potential constraints in order to offer readers a concise overview of the emerging role of nanoceria in the advancement of POC diagnostic systems for future biosensing applications.

Synergism of Edge Effect and Interlayer Engineering of VS2 on CNFs for Rapid and Precise NO2 Detection

Although two-dimensional (2D) transition-metal dichalcogenides (TMDs) exhibit attractive prospects for gas-sensing applications, the rapid and precise sensing of TMDs at low loss remains challenging. Herein, a NO2 sensor based on an expanded VS2 (VS2-E)/carbon nanofibers (CNFs) composite (abbreviated as VS2-E-C) with ultrafast response/recovery at a low-loss state is reported. In particular, the impact of the CNF content on the NO2-sensing performance of VS2-E-C was thoroughly explored. Expanded VS2 nanosheets were grafted onto the surface of hollow CNFs, and the combination boosted the charge transport, exposing abundant active edges of VS2, which enhanced the adsorption of NO2 efficiently. The activity of the VS2 edge is further confirmed by stronger NO2 adsorption with a more negative adsorption energy (-3.42 eV) and greater than the basal VS2 surface (-1.26 eV). Moreover, the exposure of rich edges induced the emergence of the expanded interlayers, which promoted the adsorption/desorption of NO2 and the interaction of gas molecules within VS2-E-C. The synergism of edge effect and interlayer engineering confers the VS2-E-C3 sensor with ultrafast response/recovery speed (9/10 s) at 60 °C, high sensitivity (∼2.50 to 15 ppm NO2), good selectivity/stability, and a low detection limit of 23 ppb. The excellent "4S" functions indicate the promising prospect of the VS2-E-C3 sensor for fast and precise NO2 detection at low-loss condition.

Ultrasensitive Bio-H2S Gas Sensor Based on Cu2O-MWCNT Heterostructures

Developing a respiratory analysis disease diagnosis platform for the H2S biomarker has great significance for the real-time detection of various diseases. However, achieving highly sensitive and rapid detection of H2S gas at the parts per billion level at low temperatures is one of the most critical challenges for developing portable exhaled gas sensors. Herein, Cu2O-multiwalled carbon nanotube (MWCNT) heterostructures with excellent gas sensitivity to H2S at room temperature and a lower temperature were successfully synthesized by a facile two-dimensional (2D) electrodeposition in situ assembly method. The combination of Cu2O and MWCNTs via the principle of optimal conductance growth not only reduced the initial resistance of the material but also provided an ideal interfacial barrier structure. Compared to the response of the pure Cu2O sensor, that of the Cu2O-MWCNT sensor to 1 ppm of H2S increased nearly 800 times at room temperature, and the response time decreased by more than 500 s. In addition to the excellent sensitivity with detection limits as low as 1 ppb, the Cu2O-MWCNT sensor was extremely selective with low-temperature adaptability. The sensor had a response value of 80.6 to 0.1 ppm of H2S at -10 °C, which is difficult to achieve with sensors based on oxygen adsorption/desorption mechanisms. The sensor was used for the detection of real oral exhaled breath, confirming its feasibility as a real-time disease monitoring sensor. The Cu2O-MWCNT heterostructures maximized the advantages of the individual components and laid the experimental foundation for future applications of highly sensitive portable breath analysis platforms for monitoring H2S.

Fluorescent nano- and microparticles for sensing cellular microenvironment: past, present and future applications

The tumor microenvironment (TME) demonstrates distinct hallmarks, including acidosis, hypoxia, reactive oxygen species (ROS) generation, and altered ion fluxes, which are crucial targets for early cancer biomarker detection, tumor diagnosis, and therapeutic strategies. Various imaging and sensing techniques have been developed and employed in both research and clinical settings to visualize and monitor cellular and TME dynamics. Among these, ratiometric fluorescence-based sensors have emerged as powerful analytical tools, providing precise and sensitive insights into TME and enabling real-time detection and tracking of dynamic changes. In this comprehensive review, we discuss the latest advancements in ratiometric fluorescent probes designed for the optical mapping of pH, oxygen, ROS, ions, and biomarkers within the TME. We elucidate their structural designs and sensing mechanisms as well as their applications in in vitro and in vivo detection. Furthermore, we explore integrated sensing platforms that reveal the spatiotemporal behavior of complex tumor cultures, highlighting the potential of high-resolution imaging techniques combined with computational methods. This review aims to provide a solid foundation for understanding the current state of the art and the future potential of fluorescent nano- and microparticles in the field of cellular microenvironment sensing.

Micellar Nanoreactors Enabled Site-Selective Decoration of Pt Nanoparticles Functionalized Mesoporous SiO2 /WO3-x Composites for Improved CO Sensing

Site-selective and partial decoration of supported metal nanoparticles (NPs) with transition metal oxides (e.g., FeOx ) can remarkably improve its catalytic performance and maintain the functions of the carrier. However, it is challenging to selectively deposit transition metal oxides on the metal NPs embedded in the mesopores of supporting matrix through conventional deposition method. Herein, a restricted in situ site-selective modification strategy utilizing poly(ethylene oxide)-block-polystyrene (PEO-b-PS) micellar nanoreactors is proposed to overcome such an obstacle. The PEO shell of PEO-b-PS micelles interacts with the hydrolyzed tungsten salts and silica precursors, while the hydrophobic organoplatinum complex and ferrocene are confined in the hydrophobic PS core. The thermal treatment leads to mesoporous SiO2 /WO3-x framework, and meanwhile FeOx nanolayers are in situ partially deposited on the supported Pt NPs due to the strong metal-support interaction between FeOx and Pt. The selective modification of Pt NPs with FeOx makes the Pt NPs present an electron-deficient state, which promotes the mobility of CO and activates the oxidation of CO. Therefore, mesoporous SiO2 /WO3-x -FeOx /Pt based gas sensors show a high sensitivity (31 ± 2 in 50 ppm of CO), excellent selectivity, and fast response time (3.6 s to 25 ppm) to CO gas at low operating temperature (66 °C, 74% relative humidity).

Hierarchical conductive metal-organic framework films enabling efficient interfacial mass transfer

Heterogeneous reactions associated with porous solid films are ubiquitous and play an important role in both nature and industrial processes. However, due to the no-slip boundary condition in pressure-driven flows, the interfacial mass transfer between the porous solid surface and the environment is largely limited to slow molecular diffusion, which severely hinders the enhancement of heterogeneous reaction kinetics. Herein, we report a hierarchical-structure-accelerated interfacial dynamic strategy to improve interfacial gas transfer on hierarchical conductive metal-organic framework (c-MOF) films. Hierarchical c-MOF films are synthesized via the in-situ transformation of insulating MOF film precursors using π-conjugated ligands and comprise both a nanoporous shell and hollow inner voids. The introduction of hollow structures in the c-MOF films enables an increase of gas permeability, thus enhancing the motion velocity of gas molecules toward the c-MOF film surface, which is more than 8.0-fold higher than that of bulk-type film. The c-MOF film-based chemiresistive sensor exhibits a faster response towards ammonia than other reported chemiresistive ammonia sensors at room temperature and a response speed 10 times faster than that of the bulk-type film.

Swarming Responsive Photonic Nanorobots for Motile-Targeting Microenvironmental Mapping and Mapping-Guided Photothermal Treatment

Micro/nanorobots can propel and navigate in many hard-to-reach biological environments, and thus may bring revolutionary changes to biomedical research and applications. However, current MNRs lack the capability to collectively perceive and report physicochemical changes in unknown microenvironments. Here we propose to develop swarming responsive photonic nanorobots that can map local physicochemical conditions on the fly and further guide localized photothermal treatment. The RPNRs consist of a photonic nanochain of periodically-assembled magnetic Fe3O4 nanoparticles encapsulated in a responsive hydrogel shell, and show multiple integrated functions, including energetic magnetically-driven swarming motions, bright stimuli-responsive structural colors, and photothermal conversion. Thus, they can actively navigate in complex environments utilizing their controllable swarming motions, then visualize unknown targets (e.g., tumor lesion) by collectively mapping out local abnormal physicochemical conditions (e.g., pH, temperature, or glucose concentration) via their responsive structural colors, and further guide external light irradiation to initiate localized photothermal treatment. This work facilitates the development of intelligent motile nanosensors and versatile multifunctional nanotheranostics for cancer and inflammatory diseases.

Ex-Solution Hybrids Functionalized on Oxide Nanofibers for Highly Active and Durable Catalytic Materials

Ex-solution catalysts containing spontaneously formed metal nanoparticles socketed on the surface of reservoir oxides have recently been employed in various research fields including catalysis and sensing, due to the process efficiency and outstanding chemical/thermal stability. However, since the ex-solution process accompanies harsh reduction heat treatment, during which many oxides undergo phase decomposition, it restricts material selection and further advancement. Herein, we propose an elaborate design principle to uniformly functionalize ex-solution catalysts at porous oxide frameworks via an electrospinning process. As a case study, we selected the ex-solved La_0.6Ca_0.4Fe_0.95Co_0.05-xNi_xO_3-δ (x = 0, 0.025 and 0.05) and SnO₂ nanofibers as ex-solution hybrids and main frameworks, respectively. We confirmed superior dimethyl sulfide (C₂H₆S) gas sensing characteristics with excellent long-cycling stability. In particular, the high catalytic activities of ex-solved CoNiFe ternary nanoparticles, strongly socketed on reservoir oxide, accelerate the spillover process of O₂ to dramatically enhance the response toward sulfuric analytes with exceptional tolerance. Altogether, our contribution represents an important stepping-stone to a rational design of ex-solved particle-reservoir oxide hybrids functionalized on porous oxide scaffolds for a variety of applications.

Low-Power, Multi-Transduction Nanosensor Array for Accurate Sensing of Flammable and Toxic Gases

Toxic and flammable gases pose a major safety risk in industrial settings; thus, their portable sensing is desired, which requires sensors with fast response, low-power consumption, and accurate detection. Herein, a low-power, multi-transduction array is presented for the accurate sensing of flammable and toxic gases. Specifically, four different sensors are integrated on a micro-electro-mechanical-systems platform consisting of bridge-type microheaters. To produce distinct fingerprints for enhanced selectivity, the four sensors operate based on two different transduction mechanisms: chemiresistive and calorimetric sensing. Local, in situ synthesis routes are used to integrate nanostructured materials (ZnO, CuO, and Pt Black) for the sensors on the microheaters. The transient responses of the four sensors are fed to a convolutional neural network for real-time classification and regression of five different gases (H₂ , NO₂ , C₂ H₆ O, CO, and NH₃ ). An overall classification accuracy of 97.95%, an average regression error of 14%, and a power consumption of 7 mW per device are obtained. The combination of a versatile low-power platform, local integration of nanomaterials, different transduction mechanisms, and a real-time machine learning strategy presented herein helps advance the constant need to simultaneously achieve fast, low-power, and selective gas sensing of flammable and toxic gases.

Several ML Algorithms and Their Feature Vector Design for Gas Discrimination and Concentration Measurement with an Ultrasonically Catalyzed MOX Sensor

Although gas-borne ultrasound catalysis has been developed as a new method to discriminate gas species and measure the concentration, applications of machine learning methods in gas analyses with a single metal oxide (MOX) gas sensor catalyzed by gas-borne ultrasound are still scarce. In this work, with an ultrasonically catalyzed MOX gas sensor, we explored the effectiveness of K-nearest neighbors (KNN), support vector machine (SVM), and single-hidden-layer BP-ANN (SHBP) in gas discrimination and the application of the SHBP in concentration measurement. The target gases in this work are ethanol, acetone, methanol, hydrogen, and n-butane in clean air, respectively, and the discrimination and concentration regression are implemented by two different ML models. With the properly designed feature vectors, the SHBP method has an acceptable capability of both of species discrimination and concentration regression (success rate of gas discrimination = 99.5%, relative error of concentration regression = 6.406%). The KNN and SVM methods have similar capabilities of gas discrimination as the SHBP. This work also demonstrates a method to design the feature vectors for the ultrasonically catalyzed MOX gas sensor and to choose the feature parameters.

Nanosensors for the diagnosis and therapy of neurodegenerative disorders and inflammatory bowel disease

One of the areas of science which has immensely advanced in the recent years is nanotechnology. This area broadly revolves around matter at scales between 1 and 100 nm, where peculiar phenomena make way for cutting-edge applications. Today, nanotechnology has a daily impact on human life with numerous and varied possible advantages. Nanosensors are one of the products of nanotechnology and any sensor that uses nanoscale phenomena qualifies to be known as a nanosensor. Nanosensors have proven very useful in a number of sectors including medical applications, food quality analysis and agricultural controlling process, etc. One of the major human healthcare applications of nanosensors is for disease diagnosis. With the aid of nanosensors, numerous neurodegenerative disorders and inflammatory diseases are commonly identified and treated of late. Alzheimer's disease (AD) and inflammatory bowel disease fall under the categories of neurodegenerative illnesses and inflammatory diseases. There are more than 20 million cases of (AD) making it the most prevalent neurological condition globally and "inflammatory bowel disease" (IBD) refers to a variety of conditions that cause persistent inflammation of the digestive tract. Here we present a comprehensive account on the utility of nanosensors for the diagnosis and treatment of (AD) and (IBD).

Temperature-Dependent n-to-p-Type Transition of 2D Mn Oxide Nanosheets toward NO2 for Flexible Gas Sensor Application

Rapid and on-site detection of nitrogen dioxide (NO₂) is important for environmental monitoring as NO₂ is a highly toxic chemical emitted from automobiles and power plants. In this study, we proposed atomically thin two-dimensional (2D) Mn oxide nanosheets (NSs) assembled on a flexible heating substrate for application in flexible and wearable NO₂ sensors. A liquid-phase exfoliation technique was used to obtain individual Mn oxide layers that formed a homogeneous suspension. A flexible heater was fabricated by partially embedding Ag nanotubes (NTs) on the surface of a colorless polyimide (CPI) film for use as a sensor substrate. Temperature-dependent NO₂ sensing properties were investigated via control of the operating temperature using a Ag NT-embedded CPI heating film. As a result, the n-type sensing behavior of the Mn oxide NSs exhibited a response [(R_gas - R_air)/R_air × 100 (%)] of 1.20 ± 0.21% for 20 ppm NO₂ at room temperature (25 °C). Meanwhile, n-p transition occurred with p-type sensing property as the operating temperature increased to 150 °C with an improved response [(R_air - R_gas)/R_air × 100 (%)] of 4.10 ± 0.42% for 20 ppm NO₂. The characteristic n-p transition of Mn oxide NSs at different operating temperatures was evidenced by the surface-adsorbed oxygen ions (i.e., O₂^- and O^-) and nitrate species (NO₃^- and NO₃^2-).

Semiconductor Plasmon Enhanced Upconversion toward a Flexible Temperature Sensor

Noninvasive and sensitive thermometry is crucial to human health monitoring and applications in disease diagnosis. Despite recent advances in optical temperature detection, the construction of sensitive wearable temperature sensors remains a considerable challenge. Here, a flexible and biocompatible optical temperature sensor is developed by combining plasmonic semiconductor W₁₈O₄₉ enhanced upconversion emission (UCNPs/WO) with flexible poly(lactic acid) (PLA)-based optical fibers. The UCNPs/WO offers highly thermal-sensitive and obviously enhanced dual-wavelength emissions for ratiometric temperature sensing. The PLA polymer endows the sensor with excellent light-transmitting ability for laser excitation and emission collection and high biocompatibility. The fabricated UCNPs/WO-PLA sensor exhibits stable and rapid temperature response in the range 298-368 K, with a high relative sensitivity of 1.53% K^-1 and detection limit as low as ±0.4 K. More importantly, this proposed sensor is demonstrated to possess dual function on real-time detection for physiological thermal changes and heat release, exhibiting great potential in wearable health monitoring and biotherapy applications.

Elastic Fibers/Fabrics for Wearables and Bioelectronics

Wearables and bioelectronics rely on breathable interface devices with bioaffinity, biocompatibility, and smart functionality for interactions between beings and things and the surrounding environment. Elastic fibers/fabrics with mechanical adaptivity to various deformations and complex substrates, are promising to act as fillers, carriers, substrates, dressings, and scaffolds in the construction of biointerfaces for the human body, skins, organs, and plants, realizing functions such as energy exchange, sensing, perception, augmented virtuality, health monitoring, disease diagnosis, and intervention therapy. This review summarizes and highlights the latest breakthroughs of elastic fibers/fabrics for wearables and bioelectronics, aiming to offer insights into elasticity mechanisms, production methods, and electrical components integration strategies with fibers/fabrics, presenting a profile of elastic fibers/fabrics for energy management, sensors, e-skins, thermal management, personal protection, wound healing, biosensing, and drug delivery. The trans-disciplinary application of elastic fibers/fabrics from wearables to biomedicine provides important inspiration for technology transplantation and function integration to adapt different application systems. As a discussion platform, here the main challenges and possible solutions in the field are proposed, hopefully can provide guidance for promoting the development of elastic e-textiles in consideration of the trade-off between mechanical/electrical performance, industrial-scale production, diverse environmental adaptivity, and multiscenario on-spot applications.

Multilevel Self-Assembly of Block Copolymers and Polymer Colloids for a Transparent and Sensitive Gas Sensor Platform

The recent emerging significance of the Internet of Things (IoT) demands sensor devices to be integrated with many different functional structures and devices while conserving their original functionalities. To this end, optical transparency and mechanical flexibility of sensor devices are critical requirements for optimal integration as well as high sensitivity. In this work, a transparent, flexible, and sensitive gas sensor building platform is introduced by using multilevel self-assembly of block copolymers (BCPs) and polystyrene (PS) colloids. For the demonstration of an H₂ gas sensor, a hierarchically porous Pd metal mesh structure is obtained by overlaying the two different patterned template structures with synergistic, distinctive characteristic length scales. The hierarchical Pd mesh shows not only high transparency over 90% but also superior sensing performance in terms of response and recovery time owing to enhanced Pd-to-hydride ratio and short H₂ diffusion lengths from the enlarged active surface areas. The hierarchical morphology also endows high mechanical flexibility while securing reliable sensing performance even under severe mechanical deformation cycles. Our scalable self-assembly based multiscale nanopatterning offers an intriguing generalized platform for many different multifunctional devices requiring hidden in situ monitoring of environmental signals.

Nanoscale Bimetallic AuPt-Functionalized Metal Oxide Chemiresistors: Ppb-Level and Selective Detection for Ozone and Acetone

As the most widely used gas sensors, metal oxide semiconductor (MOS)-based chemiresistors have been facing great challenges in achieving ppb-level and selective detection of the target gas. The rational design and employment of bimetallic nanocatalysts (NCs) are expected to address this issue. In this work, the well-shaped and monodispersed AuPt NCs (diameter ≈ 9 nm) were functionalized on one-dimensional (1D) In₂O₃ nanofibers (NFs) to construct efficient gas sensors. The sensor demonstrated dual-selective and ppb-level detection for ozone (O₃) and acetone (C₃H₆O) at different optimal working temperatures. For the possible application exploitation, a circuit was designed to monitor O₃ concentration and provide warnings when the concentration safety limit (50 ppb) was exceeded. Moreover, simulated exhaled breath measurements were also carried out to diagnose diabetes through C₃H₆O concentration. The selective detection for O₃ and C₃H₆O was further analyzed by principal component analysis (PCA). The drastically enhanced sensing performances were attributed to the synergistic catalytic effect of AuPt NCs. Both the "spillover effect" and the Schottky barrier at the interfaces of AuPt NCs and In₂O₃ NFs promoted the sensing processes of O₃ and C₃H₆O.

Advanced wearable biosensors for the detection of body fluids and exhaled breath by graphene

Given the huge economic burden caused by chronic and acute diseases on human beings, it is an urgent requirement of a cost-effective diagnosis and monitoring process to treat and cure the disease in their preliminary stage to avoid severe complications. Wearable biosensors have been developed by using numerous materials for non-invasive, wireless, and consistent human health monitoring. Graphene, a 2D nanomaterial, has received considerable attention for the development of wearable biosensors due to its outstanding physical, chemical, and structural properties. Moreover, the extremely flexible, foldable, and biocompatible nature of graphene provide a wide scope for developing wearable biosensor devices. Therefore, graphene and its derivatives could be trending materials to fabricate wearable biosensor devices for remote human health management in the near future. Various biofluids and exhaled breath contain many relevant biomarkers which can be exploited by wearable biosensors non-invasively to identify diseases. In this article, we have discussed various methodologies and strategies for synthesizing and pattering graphene. Furthermore, general sensing mechanism of biosensors, and graphene-based biosensing devices for tear, sweat, interstitial fluid (ISF), saliva, and exhaled breath have also been explored and discussed thoroughly. Finally, current challenges and future prospective of graphene-based wearable biosensors have been evaluated with conclusion. Graphene is a promising 2D material for the development of wearable sensors. Various biofluids (sweat, tears, saliva and ISF) and exhaled breath contains many relevant biomarkers which facilitate in identify diseases. Biosensor is made up of biological recognition element such as enzyme, antibody, nucleic acid, hormone, organelle, or complete cell and physical (transducer, amplifier), provide fast response without causing organ harm.

Single-Atom Tailoring of Two-Dimensional Atomic Crystals Enables Highly Efficient Detection and Pattern Recognition of Chemical Vapors

Low-dimensional semiconductor materials, such as single-walled carbon nanotubes, two-dimensional (2D) atomic crystals, and organic frameworks, have been widely adapted as ideal platforms to construct various chemo/biosensors with satisfying sensitivity. However, the general drawbacks in chemiresistive devices, including high operation temperatures, low response to low-polarity molecules, and poor selectivity, have limited their real-world applications. In this study, 2D materials (graphene, MoS₂, and WSe₂) were systematically functionalized with series of monodispersed single atomic sites (Pt, Co, and Ru) through a facile approach to construct single-atom sensors (SASs) for the detection of VOCs at room temperature. The structural and catalytic characteristics of SAs successfully translated into enhanced gas-sensing performance, with a 1-2 orders of magnitude increase in relative response to ethanol (@5 ppm) and acetone (@20 ppm) vapors (in all M-2D SASs as compared to pristine substrates), high selectivity to VOCs against relative humidity (M-WSe₂ SASs), and fast response/recovery time (11/58 s for Pt-Graphene and 22/48 s for Pt-MoS₂ to 50 ppm ethanol, 9/57 s for Pt-Graphene and 15/75 s for Pt-MoS₂ to 200 ppm acetone) that are several times faster than the pristine 2D materials. Density functional theory (DFT) calculations revealed the signaling mechanism in SASs, and the data were further trained to build machine learning (ML) models for predicting the adsorption energies and sensing performance using the features of adsorption heights, metal charge, and charge transfer between the adsorbed VOCs and SASs sites. Finally, the rich combination of the metal single atoms and 2D atomic crystal supports were converted to cross-sensitive SA sensor array that allows for detection and identification of different VOCs.

Target Convergence Analysis of Cancer-Inspired Swarms for Early Disease Diagnosis and Targeted Collective Therapy

Sensing and perception is generally a challenging aspect of decision-making. In the nanoscale, however, these processes face further complications due to the physical limitations of devising the nanomachines with more limited perception, more noise, and fewer sensors. There is, hence, higher dependence on swarm sensing and perception of many nanomachines. Here, taking hardware and software bioinspiration, we propose Chemo-Mechanical Cancer-Inspired Swarm Perception (CMCISP) based on online nano fuzzy haptic feedback for early disease diagnosis and targeted therapy. Particularly, we use epithelial cancer cell's scaffold as a carrier, its properties as a distributed perception mechanism, and its motility patterns as the swarm movements such as anti-durotaxis, blebbing, and chemotaxis. We implement the in-silico model of CMCISP using a hybrid computational framework of the cellular Potts model, swarm intelligence, and fuzzy decision-making. Furthermore, the target convergence of CMCISP is analytically proved using swarm control theory. Finally, several numerical experiments and validations for cancer target therapy, cellular stiffness measurement, anti-durotaxis movement, and robustness analysis are also conducted and compared with a mathematical chemotherapy model and authors' previous works on targeted therapy. Results show improvements of up to 57.49% in early cancer detection, 26.64% in target convergence, and 68.01% in increased normoxic cell density. The study also reveals the strategy's robustness to environmental/sensory noise by applying six SNR levels of 0, 2, 5, 10, 30, and 50 dB, with an average diagnosis error of only 0.98% and at most 2.51%.

The Need to Pair Molecular Monitoring Devices with Molecular Imaging to Personalize Health

By enabling the non-invasive monitoring and quantification of biomolecular processes, molecular imaging has dramatically improved our understanding of disease. In recent years, non-invasive access to the molecular drivers of health versus disease has emboldened the goal of precision health, which draws on concepts borrowed from process monitoring in engineering, wherein hundreds of sensors can be employed to develop a model which can be used to preventatively detect and diagnose problems. In translating this monitoring regime from inanimate machines to human beings, precision health posits that continual and on-the-spot monitoring are the next frontiers in molecular medicine. Early biomarker detection and clinical intervention improves individual outcomes and reduces the societal cost of treating chronic and late-stage diseases. However, in current clinical settings, methods of disease diagnoses and monitoring are typically intermittent, based on imprecise risk factors, or self-administered, making optimization of individual patient outcomes an ongoing challenge. Low-cost molecular monitoring devices capable of on-the-spot biomarker analysis at high frequencies, and even continuously, could alter this paradigm of therapy and disease prevention. When these devices are coupled with molecular imaging, they could work together to enable a complete picture of pathogenesis. To meet this need, an active area of research is the development of sensors capable of point-of-care diagnostic monitoring with an emphasis on clinical utility. However, a myriad of challenges must be met, foremost, an integration of the highly specialized molecular tools developed to understand and monitor the molecular causes of disease with clinically accessible techniques. Functioning on the principle of probe-analyte interactions yielding a transducible signal, probes enabling sensing and imaging significantly overlap in design considerations and targeting moieties, however differing in signal interpretation and readout. Integrating molecular sensors with molecular imaging can provide improved data on the personal biomarkers governing disease progression, furthering our understanding of pathogenesis, and providing a positive feedback loop toward identifying additional biomarkers and therapeutics. Coupling molecular imaging with molecular monitoring devices into the clinical paradigm is a key step toward achieving precision health.

Chemical Design of Activatable Photoacoustic Probes for Precise Biomedical Applications

Photoacoustic (PA) imaging technology, a three-dimensional hybrid imaging modality that integrates the advantage of optical and acoustic imaging, has great application prospects in molecular imaging due to its high imaging depth and resolution. To endow PA imaging with the ability for real-time molecular visualization and precise biomedical diagnosis, numerous activatable molecular PA probes which can specifically alter their PA intensities upon reacting with the targets or biological events of interest have been developed. This review highlights the recent developments of activatable PA probes for precise biomedical applications including molecular detection of the biotargets and imaging of the biological events. First, the generation mechanism of PA signals will be given, followed by a brief introduction to contrast agents used for PA probe design. Then we will particularly summarize the general design principles for the alteration of PA signals and activatable strategies for developing precise PA probes. Furthermore, we will give a detailed discussion of activatable PA probes in molecular detection and biomedical imaging applications in living systems. At last, the current challenges and outlooks of future PA probes will be discussed. We hope that this review will stimulate new ideas to explore the potentials of activatable PA probes for precise biomedical applications in the future.

Nanomaterials for IoT Sensing Platforms and Point-of-Care Applications in South Korea

Herein, state-of-the-art research advances in South Korea regarding the development of chemical sensing materials and fully integrated Internet of Things (IoT) sensing platforms were comprehensively reviewed for verifying the applicability of such sensing systems in point-of-care testing (POCT). Various organic/inorganic nanomaterials were synthesized and characterized to understand their fundamental chemical sensing mechanisms upon exposure to target analytes. Moreover, the applicability of nanomaterials integrated with IoT-based signal transducers for the real-time and on-site analysis of chemical species was verified. In this review, we focused on the development of noble nanostructures and signal transduction techniques for use in IoT sensing platforms, and based on their applications, such systems were classified into gas sensors, ion sensors, and biosensors. A future perspective for the development of chemical sensors was discussed for application to next-generation POCT systems that facilitate rapid and multiplexed screening of various analytes.

Volatolomics in healthcare and its advanced detection technology

Various diseases increasingly challenge the health status and life quality of human beings. Volatolome emitted from patients has been considered as a potential family of markers, volatolomics, for diagnosis/screening. There are two fundamental issues of volatolomics in healthcare. On one hand, the solid relationship between the volatolome and specific diseases needs to be clarified and verified. On the other hand, effective methods should be explored for the precise detection of volatolome. Several comprehensive review articles had been published in this field. However, a timely and systematical summary and elaboration is still desired. In this review article, the research methodology of volatolomics in healthcare is critically considered and given out, at first. Then, the sets of volatolome according to specific diseases through different body sources and the analytical instruments for their identifications are systematically summarized. Thirdly, the advanced electronic nose and photonic nose technologies for volatile organic compounds (VOCs) detection are well introduced. The existed obstacles and future perspectives are deeply thought and discussed. This article could give a good guidance to researchers in this interdisciplinary field, not only understanding the cutting-edge detection technologies for doctors (medicinal background), but also making reference to clarify the choice of aimed VOCs during the sensor research for chemists, materials scientists, electronics engineers, etc.

Electronic and morphological dual modulation of NiO by indium-doping for highly improved xylene sensing

Ultrathin indium-doped NiO nanosheets with simultaneously optimized nanostructures and electronic properties were developed to achieve a high response to a low concentration of xylene.

Bimetallic Au@Pt Nanocrystal Sensitization Mesoporous α-Fe2O3 Hollow Nanocubes for Highly Sensitive and Rapid Detection of Fish Freshness at Low Temperature

In this work, we present a new metal oxide semiconductor gas sensor for detecting trimethylamine (TMA) by bimetal Au@Pt-modified α-Fe₂O₃ hollow nanocubes (NCs) as sensing materials. The structure and morphological characteristics of Au@Pt/α-Fe₂O₃ were evaluated through multiple analyses, and their gas-sensitive performance was investigated. Compared with the pristine α-Fe₂O₃ NC sensor, the sensor based on Au@Pt/α-Fe₂O₃ NCs exhibited faster response time (5 s) and higher response (R_a/R_g = 32) toward 100 ppm TMA gas at a lower temperature (150 °C). Furthermore, we also assessed the Au@Pt/α-Fe₂O₃ NC sensor for detecting the freshness of Larimichthys crocea which have been observed by headspace solid-phase microextraction and gas chromatography-mass spectrometry. The high performance of the Au@Pt/α-Fe₂O₃ NCs is attributed to the special hollow morphology with a high specific surface area (212.9 m²/g) and the synergistic effect of the Au@Pt bimetal. The Au@Pt/α-Fe₂O₃ sensor shows promising application prospects in estimating seafood freshness on the spot.

Schottky Contacts Regularized Linear Regression for Signal Inconsistency Circumvent in Resistive Gas Micro-Nanosensors

In the frontier resistive micro-nano gas sensors, the change rate reliability between the measured quantity and output signals has long been puzzled by the ineluctable device-to-device and run-to-run disparities. Here, a neotype sensing data interpretation method to circumvent these signal inconsistencies is reported. The method is based on discovery of a strong linear relation between the initial resistance in air (R_a ) and the absolute change in resistance after exposure to target gas (R_a -R_g ). Metal oxide gas sensors based on a micro-hot-plate are employed as the model system. The study finds that such correlation has a wide universality, even for devices incorporated with different sensing materials or under different gas atmosphere. Furthermore, this rule can also be extensible to graphene-based interdigital microelectrode. In situ probe scanning analyses illuminate that the linear dependence is closely related to work function matching level between metal electrode and sensitive layer. The Schottky barrier at metal-semiconductor junctions is the prominent parameter, whose height (ϕ_B ) can fundamentally impact material/electrode contact resistance, thereby further affecting the realistic nature expression of sensing materials. Using this correlation, a calibration procedure is proposed and embed in a fully integrated pocket-size sensor prototype, whose response outcomes demonstrated high credibility as compared to commercial apparatus.

Analysis of 2D nanomaterial BC3 for COVID-19 biomarker ethyl butyrate sensor

Ethyl butyrate (EB) was identified in recent research as a prominent biomarker of COVID-19, as concentrations of EB were higher in exhaled breath of COVID-19 patients. Electronic sensitivities of pristine, Al- and Si-doped BC₃ nanosheets to the EB molecule were investigated in this study using density functional theory. It is found that the pure BC₃ was ineffective in sensing EB due to low adsorption energy and sensitivity. Aluminum- and silicon-doped BC₃ nanosheets were effective in forming a strong interaction with EB and were also sensitive. Our calculations show that the band gaps of the Al-doped and Si-doped BC₃ sheets were significantly decreased upon EB adsorption, which increased the electrical conductance of the sheets and the sensitivity. However, Si-doped BC₃ had a recovery time of almost 22 hours, making it less potent than Al-doped BC₃, which had a recovery time of just 7.7 minutes. The shorter recovery time of the Al-doped BC₃ sheet is due to its moderate adsorption energy of 25.8 kcal mol^-1. These results can help facilitate the development of an EB biosensor for COVID-19 testing and other similar applications.

Nanowire-based sensor electronics for chemical and biological applications

Detection and recognition of chemical and biological species via sensor electronics are important not only for various sensing applications but also for fundamental scientific understanding. In the past two decades, sensor devices using one-dimensional (1D) nanowires have emerged as promising and powerful platforms for electrical detection of chemical species and biologically relevant molecules due to their superior sensing performance, long-term stability, and ultra-low power consumption. This paper presents a comprehensive overview of the recent progress and achievements in 1D nanowire synthesis, working principles of nanowire-based sensors, and the applications of nanowire-based sensor electronics in chemical and biological analytes detection and recognition. In addition, some critical issues that hinder the practical applications of 1D nanowire-based sensor electronics, including device reproducibility and selectivity, stability, and power consumption, will be highlighted. Finally, challenges, perspectives, and opportunities for developing advanced and innovative nanowire-based sensor electronics in chemical and biological applications are featured.

Synergistic Integration of Chemo-Resistive and SERS Sensing for Label-Free Multiplex Gas Detection

Practical sensing applications such as real-time safety alerts and clinical diagnoses require sensor devices to differentiate between various target molecules with high sensitivity and selectivity, yet conventional devices such as oxide-based chemo-resistive sensors and metal-based surface-enhanced Raman spectroscopy (SERS) sensors usually do not satisfy such requirements. Here, a label-free, chemo-resistive/SERS multimodal sensor based on a systematically assembled 3D cross-point multifunctional nanoarchitecture (3D-CMA), which has unusually strong enhancements in both "chemo-resistive" and "SERS" sensing characteristics is introduced. 3D-CMA combines several sensing mechanisms and sensing elements via 3D integration of semiconducting SnO₂ nanowire frameworks and dual-functioning Au metallic nanoparticles. It is shown that the multimodal sensor can successfully estimate mixed-gas compositions selectively and quantitatively at the sub-100 ppm level, even for mixtures of gaseous aromatic compounds (nitrobenzene and toluene) with very similar molecular structures. This is enabled by combined chemo-resistive and SERS multimodal sensing providing complementary information.

Hybrid Porous Crystalline Materials from Metal Organic Frameworks and Covalent Organic Frameworks

Two frontier crystalline porous framework materials, namely, metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), have been widely explored owing to their outstanding physicochemical properties. While each type of framework has its own intrinsic advantages and shortcomings for specific applications, combining the complementary properties of the two materials allows the engineering of new classes of hybrid porous crystalline materials with properties superior to the individual components. Since the first report of MOF/COF hybrid in 2016, it has rapidly evolved as a novel platform for diverse applications. The state-of-art advances in the various synthetic approaches of MOF/COF hybrids are hereby summarized, together with their applications in different areas. Perspectives on the main challenges and future opportunities are also offered in order to inspire a multidisciplinary effort toward the further development of chemically diverse, multi-functional hybrid porous crystalline materials.

Surface Activity-Tuned Metal Oxide Chemiresistor: Toward Direct and Quantitative Halitosis Diagnosis

Continuous monitoring of hydrogen sulfide (H₂S) in human breath for early stage diagnosis of halitosis is of great significance for prevention of dental diseases. However, fabrication of a highly selective and sensitive H₂S gas sensor material still remains a challenge, and direct analysis of real breath samples has not been properly attempted, to the best of our knowledge. To address the issue, herein, we introduce facile cofunctionalization of WO₃ nanofibers with alkaline metal (Na) and noble metal (Pt) catalysts via the simple addition of sodium chloride (NaCl) and Pt nanoparticles (NPs), followed by electrospinning process. The Na-doping and Pt NPs decoration in WO₃ grains induces the partial evolution of the Na₂W₄O₁₃ phase, causing the buildup of Pt/Na₂W₄O₁₃/WO₃ multi-interface heterojunctions that selectively interacts with sulfur-containing species. As a result, we achieved the highest-ranked sensing performances, that is, response (R_air/R_gas) = 780 @ 1 ppm and selectivity (R_H2S/R_EtOH) = 277 against 1 ppm ethanol, among the chemiresistor-based H₂S sensors, owing to the synergistic chemical and electronic sensitization effects of the Pt NP/Na compound cocatalysts. The as-prepared sensing layer was proven to be practically effective for direct, and quantitative halitosis analysis based on the correlation (accuracy = 86.3%) between the H₂S concentration measured using the direct breath signals obtained by our test device (80 cases) and gas chromatography. This study offers possibilities for direct, highly reliable and rapid detection of H₂S in real human breath without the need of any collection or filtering equipment.

Recent Trends in Exhaled Breath Diagnosis Using an Artificial Olfactory System

Artificial olfactory systems are needed in various fields that require real-time monitoring, such as healthcare. This review introduces cases of detection of specific volatile organic compounds (VOCs) in a patient's exhaled breath and discusses trends in disease diagnosis technology development using artificial olfactory technology that analyzes exhaled human breath. We briefly introduce algorithms that classify patterns of odors (VOC profiles) and describe artificial olfactory systems based on nanosensors. On the basis of recently published research results, we describe the development trend of artificial olfactory systems based on the pattern-recognition gas sensor array technology and the prospects of application of this technology to disease diagnostic devices. Medical technologies that enable early monitoring of health conditions and early diagnosis of diseases are crucial in modern healthcare. By regularly monitoring health status, diseases can be prevented or treated at an early stage, thus increasing the human survival rate and reducing the overall treatment costs. This review introduces several promising technical fields with the aim of developing technologies that can monitor health conditions and diagnose diseases early by analyzing exhaled human breath in real time.

Confinement of Ultrasmall Bimetallic Nanoparticles in Conductive Metal-Organic Frameworks via Site-Specific Nucleation

Conductive metal-organic frameworks (cMOFs) are emerging materials for various applications due to their high surface area, high porosity, and electrical conductivity. However, it is still challenging to develop cMOFs having high surface reactivity and durability. Here, highly active and stable cMOF are presented via the confinement of bimetallic nanoparticles (BNPs) in the pores of a 2D cMOF, where the confinement is guided by dipolar-interaction-induced site-specific nucleation. Heterogeneous metal precursors are bound to the pores of 2D cMOFs by dipolar interactions, and the subsequent reduction produces ultrasmall (≈1.54 nm) and well-dispersed PtRu NPs confined in the pores of the cMOF. PtRu-NP-decorated cMOFs exhibit significantly enhanced chemiresistive NO₂ sensing performances, owing to the bimetallic synergies of PtRu NPs and the high surface area and porosity of cMOF. The approach paves the way for the synthesis of highly active and conductive porous materials via bimetallic and/or multimetallic NP loading.

Flexible Chemiresistive Cyclohexanone Sensors Based on Single-Walled Carbon Nanotube-Polymer Composites

We report a chemiresistive cyclohexanone sensor on a flexible substrate based on single-walled carbon nanotubes (SWCNTs) functionalized with thiourea (TU) derivatives. A wrapper polymer containing both 4-vinylpyridine (4VP) groups and azide groups (P(4VP-VBAz)) was employed to obtain a homogeneous SWCNT dispersion via noncovalent functionalization of SWCNTs. The P(4VP-VBAz)-SWCNT composite dispersion was then spray-coated onto an organosilanized flexible poly(ethylene terephthalate) (PET) film to achieve immobilizing quaternization between the pyridyl groups from the polymer and the functional PET substrate, thereby surface anchoring SWCNTs. Subsequent surface functionalization was performed to incorporate a TU selector into the composites, resulting in P(Q4VP-VBTU)-SWCNT, for the detection of cyclohexanone via hydrogen bonding interactions. An increase in conductance was observed as a result of the hydrogen-bonded complex with cyclohexanone resulting in a higher hole density and/or mobility in SWCNTs. As a result, a sensor device fabricated with P(Q4VP-VBTU)-SWCNT composites exhibited chemiresistive responses (ΔG/G₀) of 7.9 ± 0.6% in N₂ (RH 0.1%) and 4.7 ± 0.4% in air (RH 5%), respectively, upon exposure to 200 ppm cyclohexanone. Selective cyclohexanone detection was achieved with minor responses (ΔG/G₀ < 1.4% at 500 ppm) toward interfering volatile organic compounds (VOC). analytes. We demonstrate a robust sensing platform using the polymer-SWCNT composites on a flexible PET substrate for potential application in wearable sensors.

Large-area synthesis of nanoscopic catalyst-decorated conductive MOF film using microfluidic-based solution shearing

Conductive metal-organic framework (C-MOF) thin-films have a wide variety of potential applications in the field of electronics, sensors, and energy devices. The immobilization of various functional species within the pores of C-MOFs can further improve the performance and extend the potential applications of C-MOFs thin films. However, developing facile and scalable synthesis of high quality ultra-thin C-MOFs while simultaneously immobilizing functional species within the MOF pores remains challenging. Here, we develop microfluidic channel-embedded solution-shearing (MiCS) for ultra-fast (≤5 mm/s) and large-area synthesis of high quality nanocatalyst-embedded C-MOF thin films with thickness controllability down to tens of nanometers. The MiCS method synthesizes nanoscopic catalyst-embedded C-MOF particles within the microfluidic channels, and simultaneously grows catalyst-embedded C-MOF thin-film uniformly over a large area using solution shearing. The thin film displays high nitrogen dioxide (NO₂) sensing properties at room temperature in air amongst two-dimensional materials, owing to the high surface area and porosity of the ultra-thin C-MOFs, and the catalytic activity of the nanoscopic catalysts embedded in the C-MOFs. Therefore, our method, i.e. MiCS, can provide an efficient way to fabricate highly active and conductive porous materials for various applications.

The immobilization of catalysts within the pores of conductive metal-organic frameworks (C-MOFs) via facile and scalable methodologies remains challenging. Here the authors report a microfluidic channel-embedded solution shearing process that enables the high throughput, large-area, single-step preparation of Pt nanocatalyst-embedded C-MOF thin films.

Ratio-Adjustable Upconversion Luminescence Nanoprobe for Ultrasensitive In Vitro Diagnostics

The development of precise medicine requires diagnostic probes to simultaneously satisfy an excellent detection limit and a wide linear analysis range because of enormous individual-discrepancy of disease biomarker concentrations, yet it remains challenging. Herein, an upconverison nanoprobe with a luminescence ratio flexibly tailored was designed for ultrasensitive monitoring exhaled nitric oxide to indicate the clinical course of asthma. Two independent emissions from the same nanoprobe can be discretionarily modulated to vary their intensity ratios for adapting different analysis requirements. Delightfully, this novel nanoprobe demonstrated a 100-fold lower detection limit compared with the traditional ratiometric fluorescence manner and a more broad linear detection range from the subpart per billion (ppb) level to hundreds of ppb. This ratio-adjustable fluorescence detection strategy holds great potential for miscellaneous disease diagnosis applications.

Gas sensing materials roadmap

Gas sensor technology is widely utilized in various areas ranging from home security, environment and air pollution, to industrial production. It also hold great promise in non-invasive exhaled breath detection and an essential device in future internet of things. The past decade has witnessed giant advance in both fundamental research and industrial development of gas sensors, yet current efforts are being explored to achieve better selectivity, higher sensitivity and lower power consumption. The sensing layer in gas sensors have attracted dominant attention in the past research. In addition to the conventional metal oxide semiconductors, emerging nanocomposites and graphene-like two-dimensional materials also have drawn considerable research interest. This inspires us to organize this comprehensive 2020 gas sensing materials roadmap to discuss the current status, state-of-the-art progress, and present and future challenges in various materials that is potentially useful for gas sensors.

Colorimetric Dye-Loaded Nanofiber Yarn: Eye-Readable and Weavable Gas Sensing Platform

The colorimetric gas sensor offers an opportunity for the simple and rapid detection of toxic gaseous substances based on visually discernible changes in the color of the sensing material. In particular, the accurate detection of trace amounts of certain biomarkers in a patient's breath provides substantial clues regarding specific diseases, for example, hydrogen sulfide (H₂S) for halitosis and ammonia (NH₃) for kidney disorder. However, conventional colorimetric sensors often lack the sensitivity, selectivity, detection limit, and mass-productivity, impeding their commercialization. Herein, we report an inexpensive route for the meter-scale synthesis of a colorimetric sensor based on a composite nanofiber yarn that is chemically functionalized with an ionic liquid as an effective H₂S adsorbent and lead acetate as a colorimetric dye. As an eye-readable and weavable sensing platform, the single-strand yarn exhibits enhanced sensitivity supported by its high surface area and well-developed porosity to detect the breath biomarker (1 ppm of H₂S). Alternatively, the yarn loaded with lead iodide dyes could reversibly detect NH₃ gas molecules in the ppm-level, demonstrating the facile extensibility. Finally, we demonstrated that the freestanding yarns could be sewn into patterned textiles for the fabrication of a wearable toxic gas alarm system with a visual output.

Nanotechnology in pulmonary medicine

Nanotechnology in medicine—nanomedicine—is extensively employed to diagnose, treat, and prevent pulmonary diseases. Over the last few years, this brave new world has made remarkable progress, offering opportunities to address historical clinical challenges in pulmonary diseases including multidrug resistance, adverse side effects of conventional therapeutic agents, novel imaging, and earlier disease detection. Nanomedicine is also being applied to tackle the new emerging infectious diseases, including severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East Respiratory Syndrome Coronavirus (MERS-CoV), influenza A virus subtype H1N1 (A/H1N1), and more recently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this review we provide both a historical overview of the application of nanomedicine to respiratory diseases and more recent cutting-edge approaches such as nanoparticle-mediated combination therapies, novel double-targeted nondrug delivery system for targeting, stimuli-responsive nanoparticles, and theranostic imaging in the diagnosis and treatment of pulmonary diseases.