Ultrasensitive Chemical Sensors Research Articles

Selective sensing of DNA/RNA nucleobases by metal-functionalized silicon nanowires: A DFT approach

Ultrasensitive chemical sensors based on silicon nanowires (SiNW) are optimal for detection of biological species, since they are fast and non-invasive, their fabrication is compatible with current semiconductor technology, and silicon is a biocompatible material. SiNW-based DNA sensors are well known, but there are few studies regarding the interaction of SiNWs with the single DNA/RNA nucleobases: Guanine (G), Cytosine (C), Adenine (A), Thymine (T), and Uracil (U). This work uses Density Functional Theory to study the interaction between the single nucleobases and SiNWs decorated with Cu, Ag and Au atoms, to determine their potential use as nucleobase detectors or carriers, or even to use nucleobase-functionalized SiNWs as sensing platform for other chemical species. Numerical results show remarkable changes of the nanowire's band gap upon adsorption of nucleobases. Likewise, the adsorption energies of the nucleobases on the functionalized SiNW follow the trend C > G > A > T > U. Cu-functionalized nanowires are suitable for the electrical detection of cytosine, while Au-functionalized nanowires may detect thymine and uracil. On the other hand, large variations of the nanowire work function were found when guanine and adenine are adsorbed on Cu-functionalized nanowires.

Graphene-integrated toroidal resonance metasurfaces used for picogram-level detection of chlorothalonil in the terahertz region.

Toroidal dipole resonance can significantly reduce radiation loss of materials, potentially improving sensor sensitivity. Generally, toroidal dipole response is suppressed by electric and magnetic dipoles in natural materials, making it difficult to observe experimentally. However, as 2D metamaterials, metasurfaces can weaken the electric and magnetic dipole, enhancing toroidal dipole response. Here, we propose a new graphene-integrated toroidal resonance metasurface as an ultra-sensitive chemical sensor, capable of qualitative detection of chlorothalonil in the terahertz region, down to a detection limit of 100 pg/mL. Our results demonstrate graphene-integrated toroidal resonance metasurfaces as a promising basis for ultra-sensitive, qualitative detection in chemical and biological sensing.

The frontiers of functionalized graphene-based nanocomposites as chemical sensors

Abstract Graphene is a single-atom-thick sheet of sp2 hybridized carbon atoms that are packed in a hexagonal honeycomb crystalline structure. This promising structure has endowed graphene with advantages in electrical, thermal, and mechanical properties such as room-temperature quantum Hall effect, long-range ballistic transport with around 10 times higher electron mobility than in Si and thermal conductivity in the order of 5,000 W/mK, and high electron mobility at room temperature (250,000 cm2/V s). Another promising characteristic of graphene is large surface area (2,630 m2/g) which has emerged so far with its utilization as novel electronic devices especially for ultrasensitive chemical sensor and reinforcement for the structural component applications. The application of graphene is challenged by concerns of synthesis techniques, and the modifications involved to improve the usability of graphene have attracted extensive attention. Therefore, in this review, the research progress conducted in the previous decades with graphene and its derivatives for chemical detection and the novelty in performance enhancement of the chemical sensor towards the specific gases and their mechanism have been reviewed. The challenges faced by the current graphene-based sensors along with some of the probable solutions and their future improvements are also being included.

Hydrogel Interferometry for Ultrasensitive and Highly Selective Chemical Detection.

Developing ultrasensitive chemical sensors with small scale and fast response through simple design and low-cost fabrication is highly desired but still challenging. Herein, a simple and universal sensing platform based on a hydrogel interferometer with femtomol-level sensitivity in detecting (bio)chemical molecules is demonstrated. A unique local concentrating effect (up to 109 folds) in the hydrogel induced by the strong analyte binding and large amount of ligands, combined with the signal amplification effect by optical interference, endows this platform with an ultrahigh sensitivity, specifically 10-14 m for copper ions and 1.0 × 10-11 mg mL-1 for glycoprotein with 2-4 order-of-magnitude enhancement. The specific chemical reactions between selected ligands and target analytes provide high selectivity in detecting complex fluids. This universal principle with broad chemistry, simple physics, and modular design allows for high performance in detecting wide customer choices of analytes, including metal ions and proteins. The scale of the sensor can be down to micrometer size. The nature of the soft gel makes this platform transparent, flexible, stretchable, and compatible with a variety of substrates, showing high sensing stability and robustness after 200 cycles of bending or stretching. The outstanding sensing performance grants this platform great promise in broad practical applications.

A flexible, ultra-sensitive chemical sensor with 3D biomimetic templating for diabetes-related acetone detection.

The structural features of biological organisms have evolved through natural selection to provide highly tailored functions, inspiring numerous biomimetic and biological design strategies. A wide scope of untapped potential lies in harnessing the nanoscale architectural properties of natural biological materials to develop high-performance sensors. Herein, we report the development of an ultrasensitive chemical sensor that is based on the three-dimensional (3D) biomimetic templating of a structurally hierarchical butterfly wing. In conjunction with graphene sheet coating strategies, the porous 3D architecture enables highly selective detection of diabetes-related volatile organic compounds (VOCs), including a rapid response time (≤1 s), a low limit of detection (20 ppb), and superior mechanical properties. Taken together, the findings in this work demonstrate the promise of incorporating natural biological materials into high-performance sensors, with excellent potential for wearable and flexible sensors.

Ultrasensitive Gas-Phase Chemical Sensing Based on Functionalized Photonic Crystal Nanobeam Cavities

Photonic crystal nanobeam cavities with high-quality factors are very sensitive to the changes of the dielectric properties of their surroundings. Utilizing this high sensitivity and by applying chemical functionalization, an ultrasensitive chemical sensor for gases based on a nanobeam cavity was demonstrated. A limit of detection of 1.5 parts-per-billion (ppb) in ambient conditions, determined from the noise level of the system, was achieved for nerve agent simulant methyl salicylate. The nanobeam cavity's nonlinear thermo-optical bistability is also utilized to realize a threshold detector for cumulative chemical exposure.

Direct integration of carbon nanotubes in Si microstructures

In this paper we present a low-cost, room-temperature process for integrating carbon nanotubes on Si microsystems. The process uses localized resistive heating by controlling current through suspended microbridges, to provide local temperatures high enough for CVD growth of carbon nanotubes. Locally grown carbon nanotubes make electrical connections through guidance by electric fields, thus eventually making circuits. The process is scalable to a wafer level batch process. Furthermore, it is controlled electrically, thus enabling automated control. Direct integration of carbon nanotubes in microstructures has great promise for nano-functional devices, such as ultrasensitive chemical sensors. Initial measurements demonstrate the Si–carbon nanotube–Si circuit's potential as a NH3 sensor.

DNA-decorated carbon nanotube-based FETs as ultrasensitive chemical sensors: Discrimination of homologues, structural isomers, and optical isomers

We have explored the abilities of all-electronic DNA-carbon nanotube (DNA-NT) vapor sensors to discriminate very similar classes of molecules. We screened hundreds of DNA-NT devices against a panel of compounds chosen because of their similarities. We demonstrated that DNA-NT vapor sensors readily discriminate between series of chemical homologues that differ by single methyl groups. DNA-NT devices also discriminate among structural isomers and optical isomers, a trait common in biological olfactory systems, but only recently demonstrated for electronic FET based chemical sensors.

ChemInform Abstract: Graphene Field‐Effect Transistors: Electrochemical Gating, Interfacial Capacitance, and Biosensing Applications

AbstractReview: 70 refs.

Ultrasensitive chemical sensors based on whispering gallery modes in a microsphere coated with zeolite

We propose a highly sensitive chemical sensor by functionally coating a zeolite film on the external surface of an optical microsphere. Using the perturbation theory, a model is developed to calculate sensor sensitivity and analyze the impact of the zeolite film thickness. The quality factor and detection limit are also investigated by using an approximate model. Simulations show that a zeolite coating can effectively increase sensitivity. The results provide physical insights for the design and optimization of various parameters for desired sensor performance.

Electrospinning of Nanomaterials and Applications in Electronic Components and Devices

Electrospinning of nanomaterial composites are gaining increased interest in the fabrication of electronic components and devices. Performance improvement of electrospun components results from the unique properties associated with nanometer-scaled features, high specific surface areas, and light-weight designs. Electrospun nanofiber membrane-containing polymer electrolytes show improved ionic conductivity, electrochemical stability, low interfacial resistance, and improved charge-discharge performance than those prepared from conventional membranes. Batteries with non-woven electrospun separators have increased cycle life and higher rate capabilities than ones with conventional separators. Electrospun nanofibers may also be used as working electrodes in lithium-ion batteries, where they exhibit excellent rate capability, high reversible capacity, and good cycling performance. Moreover, the high surface area of electrospun activated carbon nanofibers improves supercapacitor energy density. Similarly, nanowires having quasi-one-dimensional structures prepared by electrospinning show high conductivity and have been used in ultra-sensitive chemical sensors, optoelectronics, and catalysts. Electrospun conductive polymers can also perform as flexible electrodes. Finally, the thin, porous structure of electrospun nanofibers provides for the high strain and fast response required for improved actuator performance. The current review examines recent advances in the application of electrospinning in fabricating electronic components and devices.

Graphene Field‐Effect Transistors: Electrochemical Gating, Interfacial Capacitance, and Biosensing Applications

Single-layer graphene has received much attention because of its unique two-dimensional crystal structure and properties. In this review, we focus on the graphene devices in solution, and their properties that are relevant to chemical and biological applications. We will discuss their charge transport, controlled by electrochemical gates, interfacial and quantum capacitance, charged impurities, and surface potential distribution. The sensitive dependence of graphene charge transport on the surrounding environment points to their potential applications as ultrasensitive chemical sensors and biosensors. The interfacial and quantum capacitance studies are directly relevant to the on-going effort of creating graphene-based ultracapacitors for energy storage.

Detection of trace organophosphorus vapor with a self-assembled bilayer functionalized SiO 2 microcantilever piezoresistive sensor

Using piezoresistive SiO 2 microcantilever technology, we present an ultra-sensitive chemical sensor for trace organophosphorus vapor detection. A self-assembled composite layer of Cu 2+/11-mercaptoundecanoic acid is modified on the surface of the sensing cantilever as a specific coating to capture P O containing compounds. Experimental results indicate that the sensor can be quite sensitive to DMMP vapor (well known as a simulant of nerve agent). The signal-noise-limited detection resolution of the sensor is experimentally obtained as low as several parts per billion. Besides that the sensor can yield reversible and repeatable response to DMMP vapor, adsorption of DMMP on the self-assembled composite layer is well fit to the Langmuir isotherm model.

Screening and Enrichment of Metal Nanoparticles with Novel Optical Properties

A rapid screening and enrichment method is reported for exploring the size and shape diversities (libraries) of nanometer-scale colloidal particles. With the use of surface-enhanced Raman scattering, a new class of metal nanoparticles has been identified from heterogeneous silver colloids. These particles are relatively large, faceted nanocrystals that are able to enhance the efficiencies of surface optical processes by as much as 14−15 orders of magnitude. The population of these novel nanoparticles is only about 0.1−1% in standard colloid preparations but can be enriched to about 10−15% by size-selective fractionation. This new class of nanoparticles could find potential uses in optoelectronic devices, ultrasensitive chemical sensors, and single-molecule detection.

Conductive Polymer Films as Ultrasensitive Chemical Sensors for Hydrazine and Monomethylhydrazine Vapor

Thin films of the electrically conductive polymer poly(3-hexylthiophene) were investigated as ultrasensitive chemical sensors for hydrazine and monomethylhydrazine vapor. The threshold limit value for these highly toxic species, which are used extensively as rocket fuels, has recently been lowered to 10 ppb for 8-h exposure, necessitating the development of instrumentation with improved sensitivity. The present study describes the fabrication, calibration, and testing of simple, rugged, polymer-based sensors for detection of hydrazines in both ambient and vacuum environments. For reasonable choices of film thickness, initial resistance, and integration time, it is demonstrated that concentrations in the 0.1-100 ppb range can be monitored with an accuracy of ±20%. The sensor can be utilized for both dosimetric and real-time detection. Reproducible fabrication was achieved using standard spin-coating techniques. The polymer sensors exhibit good specificity to hydrazines in the presence of NH(3), amines, and ambient H(2)O and have a shelf-life of several years when stored in cold, dry conditions.