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A new type of carbonized polymer dot was prepared by the one-step hydrothermal method of triethoxylsilane (TEOS) and citric acid (CA). The sensor made from carbonized polymer dots (CPDs) showed superior gas sensing performance toward ammonia at room temperature. The Si, O-codoped CPDs exhibited superior ammonia sensing performance at room temperature, including a low practical limit of detection (pLOD) of 1 ppm ( R a / R g : 1.10, 1 ppm), short response/recovery time (30/36 s, 1 ppm), high humidity resistance (less than 5% undulation when changing relative humidity to 80 from 30%), high stability (less than 5% initial response undulation after 120 days), reliable repeatability, and high selectivity against other interferential gases. The gas sensing mechanism was investigated through control experiments and in situ FTIR, indicating that Si, O-codoping essentially improves the electron transfer capability of CPDs and synergistically dominates the superior ammonia sensing properties of the CPDs. This work presents a facile strategy for constructing novel high-performance, single-component carbonized polymer dots for gas sensing.

For gas sensing applications, most of the reported two-dimensional (2D) materials are suffering from relatively low sensitivity and high limit of detection (LOD) at room temperature. In this work, we selected rhenium disulfide (ReS 2 ) nanosheets to fabricate ReS 2 transistor-based gas sensors (RTGSs) with ultrahigh sensitivity and low LOD toward nitrogen dioxide (NO 2 ). The ReS 2 nanosheets with different thicknesses were prepared via mechanical exfoliation and all-dry transfer method. Under 405 nm light illumination at room temperature (25 °C), the fabricated gas sensors showed a significant enhancement of the response with full reversibility toward ppb level NO 2 (response of 9.07 at 500 ppb, a LOD of 50 ppb). In particular, the total response and recovery time of the RTGS was revealed to be less than 4 minutes (55 and 180 s, respectively), which is one of the top three shortest response and recovery times toward ppb level NO 2 of the reported 2D material-based room-temperature gas sensors so far. Via Raman spectrometry, Kelvin probe force microscopy (KPFM), and X-ray photoelectron spectrometry (XPS), the structure and gas sensing mechanism of the materials were systematically investigated. It was confirmed that the electrons transfer from the ReS 2 surface to NO 2 molecules, inducing the hole doping of ReS 2 , which consequently increased the sensor resistance. Moreover, the concentration of the photogenerated carriers in ReS 2 would accordingly be promoted by light illumination, which accounts for the substantial light enhancement of the gas sensing performance of RTGSs.

Combining the stability of solid-state nanopores with the unique sensing properties of biological components in a miniaturized electrical hybrid nanopore device is a challenging approach to advance the sensitivity and selectivity of small-molecule detection in healthcare and environment analytics. Here, we demonstrate a simple method to design an electrical hybrid nanosensor comprising a bacterial binding protein tethered to a solid-state nanopore allowing high-affinity detection of phosphonates. The diverse family of bacterial substrate-binding proteins (SBPs) binds specifically and efficiently to various substances and has been implicated as an ideal biorecognition element for analyte detection in the design of hybrid bionanosensors. Here, we demonstrate that the coupling of the purified phosphonate binding protein PhnD via primary amines to the reactive NHS groups of P(DMAA- co -NMAS) polymers inside a single track-etched nanopore in poly(ethylene terephthalate) (PET) foils results in ligand-specific and concentration-dependent changes in the nanopore current. Application of the phosphonate 2-aminoethylphosphonate (2AEP) or ethylphosphonate (EP) induces a large conformational rearrangement in PnhD around the hinge in a venus flytrap mechanism resulting in a concentration depended on increase of the single pore current with binding affinities of 27 and 373 nM, respectively. Thus, the specificity and stability of this simple hybrid sensor concept combine the advantages of both, the diversity of ligand-specific substrate-binding proteins and solid-state nanopores encouraging further options to produce robust devices amenable to medical or environmental high-throughput-based applications in nanotechnology.