Superior Self‐Powered Room‐Temperature Chemical Sensing with Light‐Activated Inorganic Halides Perovskites

Hybrid halide perovskite is one of the promising light absorber and is intensively investigated for many optoelectronic applications. Here, the first prototype of a self‐powered inorganic halides perovskite for chemical gas sensing at room temperature under visible‐light irradiation is presented. These devices consist of porous network of CsPbBr₃ (CPB) and can generate an open‐circuit voltage of 0.87 V under visible‐light irradiation, which can be used to detect various concentrations of O₂ and parts per million concentrations of medically relevant volatile organic compounds such as acetone and ethanol with very quick response and recovery time. It is observed that O₂ gas can passivate the surface trap sites in CPB and the ambipolar charge transport in the perovskite layer results in a distinct sensing mechanism compared with established semiconductors with symmetric electrical response to both oxidizing and reducing gases. The platform of CPB‐based gas sensor provides new insights for the emerging area of wearable sensors for personalized and preventive medicine.     

Self‐Powered Chemical Sensing Driven by Graphene‐Based Photovoltaic Heterojunctions with Chemically Tunable Built‐In Potentials

Ultralow power chemical sensing is essential toward realizing the Internet of Things. However, electrically driven sensors must consume power to generate an electrical readout. Here, a different class of self‐powered chemical sensing platform based on unconventional photovoltaic heterojunctions consisting of a top graphene (Gr) layer in contact with underlying photoactive semiconductors including bulk silicon and layered transition metal dichalcogenides is proposed. Owing to the chemically tunable electrochemical potential of Gr, the built‐in potential at the junction is effectively modulated by absorbed gas molecules in a predictable manner depending on their redox characteristics. Such ability distinctive from bulk photovoltaic counterparts enables photovoltaic‐driven chemical sensing without electric power consumption. Furthermore, it is demonstrated that the hydrogen (H₂) sensing properties are independent of the light intensity, but sensitive to the gas concentration down to the 1 ppm level at room temperature. These results present an innovative strategy to realize extremely energy‐efficient sensors, providing an important advancement for future ubiquitous sensing.     

Chemical and Physical Sensing by Organic Field‐Effect Transistors and Related Devices

Organic semiconductor films are susceptible to noncovalent interactions, trapping and doping, photoexcitation, and dimensional deformation. While these effects can be detrimental to the performance of conventional circuits, they can be harnessed, especially in field‐effect architectures, to detect chemical and physical stimuli. This Review summarizes recent advances in the use of organic electronic materials for the detection of environmental chemicals, pressure, and light. The material features that are responsible for the transduction of the input signals to electronic information are discussed in detail.     

Microlandscaping of Au Nanoparticles on Few‐Layer MoS2 Films for Chemical Sensing

Surface modification or decoration of ultrathin MoS₂ films with chemical moieties is appealing since nanointerfacing can functionalize MoS₂ films with bonus potentials. In this work, a facile and effective method for microlandscaping of Au nanoparticles (NPs) on few‐layer MoS₂ films is developed. This approach first employs a focused laser beam to premodify the MoS₂ films to achieve active surface domains with unbound sulfur. When the activated surface is subsequently immersed in AuCl₃ solution, Au NPs are found to preferentially decorate onto the modified regions. As a result, Au NPs can be selectively and locally anchored onto designated regions on the MoS₂ surface. With a scanning laser beam, microlandscapes comprising of Au NPs decorated on laser‐defined micropatterns are constructed. By varying the laser power, reaction time and thickness of the MoS₂ films, the size and density of the NPs can be controlled. The resulting hybrid materials are demonstrated as efficient Raman active surfaces for the detection of aromatic molecules with high sensitivity.     

Distinct Mechanisms of DNA Sensing Based on N‐Doped Carbon Nanotubes with Enhanced Conductance and Chemical Selectivity

N‐doped capped carbon nanotube (CNT) electrodes applied to DNA sequencing are studied by first‐principles calculations. For the face‐on nucleobase junction configurations, a conventional conductance ordering is obtained where the largest signal results from guanine according to its high highest occupied molecular orbital (HOMO) level, whereas for the edge‐on counterparts a distinct conductance ordering is observed where the low‐HOMO thymine provides the largest signal. The edge‐on mode is shown to operate based on a novel molecular sensing mechanism that reflects the chemical connectivity between N‐doped CNT caps that can act both as electron donors and electron acceptors and DNA functional groups that include the hyperconjugated thymine methyl group.     

Site‐Specific Self‐Assembled Liquid‐Gated ZnO Nanowire Transistors for Sensing Applications

A scalable bottom‐up solution‐based approach for the site‐specific realization of ZnO nanowire (ZnO‐NW)‐based field‐effect transistors for sensing applications in liquids is reported. The nanowires are grown across predefined electrodes patterned by photolithography. Site specificity is attained by the use of nanoparticles acting as seeds. Using integrated on‐chip microchannels and microfabricated gate electrodes, electrochemically gated ZnO‐NW network transistors functioning in liquids are demonstrated. The optimized devices are rendered sensitive to pH through chemical functionalization. The unique combination of the sensitivity, site specificity, scalability, and cost effectiveness of the technique opens up avenues for the routine realization of one‐dimensional nanostructure‐based chemical and biosensors for analytical and diagnostic applications.     

Ball‐Mill‐Exfoliated Graphene: Tunable Electrochemistry and Phenol Sensing

A simple wet ball‐milling method for exfoliating pristine graphite to graphene nanosheets is proposed. The surfactant of cetyltrimethyl ammonium bromide is utilized to greatly improve the exfoliation efficiency of graphene nanosheets. Variation of the ball‐milling time is an efficient way to control the size and thickness of graphene nanosheets, as well as the level of edge defects. With an increase of ball‐milling time, superior electrochemical reactivity is imparted owing to enlarged active area and increased catalytic ability. The obtained graphene nanosheets are sensitive for electrochemical oxidation of phenols (e.g., hydroquinone, p‐chlorophenol, and p‐nitrophenol), and thus qualified for the simultaneous sensing of trace level of phenols. The detection limits of simultaneous monitoring of hydroquinone, p‐chlorophenol, and p‐nitrophenol are as low as 0.017, 0.024, and 0.42 mg L^?1, respectively. The proposed strategy thus opens up a new way to tune electrochemistry of graphene materials as well as to design their new applications.