Microchip gas chromatography column using magnetic beads coated with polydimethylsiloxane and metal organic frameworks.

Micro gas chromatography (μGC) using microfabricated silicon columns has been developed in response to the requirement for portable on-site gas analysis. Although different stationary phases have been developed, repeatable and reliable surface coatings in these rather small microcolumns remains a challenge. Herein, a new stationary phase coating strategy using magnetic beads (MBs) as carriers for micro column is presented.

On-Chip Monolithic Integrated Multimode Carbon Nanotube Sensor for a Gas Chromatography Detector.

Carbon nanotube (CNT)-based chemiresistors are promising gas detectors for gas chromatography (GC) due to their intrinsic nanoscale porosity and excellent electrical conductivity. However, fabrication reproducibility, long desorption time, limited sensitivity, and low dynamic range limit their usage in real applications. This paper reports a novel on-chip monolithic integrated multimode CNT sensor, where a micro-electro-mechanical system-based bulk acoustic wave (BAW) resonator is embedded underneath a CNT chemiresistor.

In-Line Detection with Microfluidic Bulk Acoustic Wave Resonator Gas Sensor for Gas Chromatography.

A microfluidic film bulk acoustic wave resonator gas sensor (mFBAR) adapted specifically as an in-line detector in gas chromatography was described. This miniaturized vapor sensor was a non-destructive detector with very low dead volume (0.02 μL).

Surface Engineering of Metal-Organic Framework Prepared on Film Bulk Acoustic Resonator for Vapor Detection.

Gravimetric resonators based on micro/nanoelectromechanical systems (M/NEMS) are potential candidates in developing smaller, less expensive, and higher-performance gas sensors. Metal-organic frameworks (MOFs) with high surface areas have recently come into focus as advanced nanoporous sensitive materials in microgravimetric gas sensors. The surface of MOFs on those sensors is critical in offering water stability and varying absorption behaviors.

A Fully Integrated Wireless Flexible Ammonia Sensor Fabricated by Soft Nano-Lithography.

Flexible ammonia (NH) sensors based on one-dimensional nanostructures have attracted great attention due to their high flexibility and low power consumption. However, it is still challenging to reliably and cost-effectively fabricate ordered nanostructure-based flexible sensors. Herein, a smartphone-enabled fully integrated system based on a flexible nanowire sensor was developed for real-time NH monitoring.

Hierarchical assembly of gold nanorod stripe patterns for sensing and cells alignment.

Hierarchical assemblies of nanomaterial superstructures with controlled orientation affords a multitude of novel properties of plasmonics and broad applications. Yet constructing multi-functional superstructures with nanoparticles positioned in desired locations remains challenging. Herein, gold nanorods (GNRs) assembled in stripe patterns with controlled orientation and structures in millimeter scale for versatile application have been achieved.

A chemiresistive sensor array from conductive polymer nanowires fabricated by nanoscale soft lithography.

One-dimensional organic nanostructures are essential building blocks for high performance gas sensors. Constructing an e-nose type sensor array is the current golden standard in developing portable systems for the detection of gas mixtures. However, facile fabrication of nanoscale sensor arrays is still challenging due to the high cost of the conventional nanofabrication techniques.

Dual-Mode Gas Sensor Composed of a Silicon Nanoribbon Field Effect Transistor and a Bulk Acoustic Wave Resonator: A Case Study in Freons.

In this paper, we develop a novel dual-mode gas sensor system which comprises a silicon nanoribbon field effect transistor (Si-NR FET) and a film bulk acoustic resonator (FBAR). We investigate their sensing characteristics using polar and nonpolar organic compounds, and demonstrate that polarity has a significant effect on the response of the Si-NR FET sensor, and only a minor effect on the FBAR sensor. In this dual-mode system, qualitative discrimination can be achieved by analyzing polarity with the Si-NR FET and quantitative concentration information can be obtained using a polymer-coated FBAR with a detection limit at the ppm level.

Conductive polymer nanowire gas sensor fabricated by nanoscale soft lithography.

Resistive devices composed of one-dimensional nanostructures are promising candidates for the next generation of gas sensors. However, the large-scale fabrication of nanowires is still challenging, which restricts the commercialization of such devices. Here, we report a highly efficient and facile approach to fabricating poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) nanowire chemiresistive gas sensors by nanoscale soft lithography.

Smartphone-Enabled Colorimetric Trinitrotoluene Detection Using Amine-Trapped Polydimethylsiloxane Membranes.

A smartphone-enabled platform for easy and portably colorimetric analysis of 2,4,6-trinitrotoluene (TNT) using amine-trapped PDMS is designed and implemented. The amine-trapped polydimethylsiloxane (PDMS) is simply prepared by immersing the cured PDMS in aminosilane solutions forming an amine-containing polymer. After contacting with TNT-containing solutions, the colorless PDMS showed a rapid colorimetric change which can be easily identified by the naked eye.

Detection of Volatile Organic Compounds by Self-assembled Monolayer Coated Sensor Array with Concentration-independent Fingerprints.

In this paper, we have modeled and analyzed affinities and kinetics of volatile organic compounds (VOCs) adsorption (and desorption) on various surface chemical groups using multiple self-assembled monolayers (SAMs) functionalized film bulk acoustic resonator (FBAR) array. The high-frequency and micro-scale resonator provides improved sensitivity in the detections of VOCs at trace levels. With the study of affinities and kinetics, three concentration-independent intrinsic parameters (monolayer adsorption capacity, adsorption energy constant and desorption rate) of gas-surface interactions are obtained to contribute to a multi-parameter fingerprint library of VOC analytes.

Detection of Volatile Organic Compounds Using Microfabricated Resonator Array Functionalized with Supramolecular Monolayers.

This paper describes the detection of volatile organic compounds (VOCs) using an e-nose type integrated microfabricated sensor array, in which each resonator is coated with different supramolecular monolayers: p-tert-butyl calix[8]arene (Calix[8]arene), 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine (Porphyrin), β-cyclodextrin (β-CD), and cucurbit[8]uril (CB[8]). Supramolecular monolayers fabricated by Langmuir-Blodgett techniques work as specific sensing interface for different VOCs recognition which increase the sensor selectivity. Microfabricated ultrahigh working frequency film bulk acoustic resonator (FBAR) transducers (4.

Tuning the resonant frequency of resonators using molecular surface self-assembly approach.

In this work, a new method to tune the resonant frequency of microfabricated resonator using molecular layer-by-layer (LbL) self-assembly approach is demonstrated. By simply controlling the polymer concentration and the number of layers deposited, precisely tuning the frequency of microfabricated resonators is realized. Due to its selective deposition through specific molecular recognitions, such technique avoids the high-cost and complex steps of conventional semiconductor fabrications and is able to tune individual diced device.

6,13-dibromopentacene [2,3:9,10]-bis(dicarboximide): a versatile building block for stable pentacene derivatives.

6,13-Dibromopentacene [2,3:9,10]-bis(dicarboximide) (1) was synthesized for the first time by using in situ generated benzo[1,2-c:4,5-c']difuran as a key intermediate. Compound 1 exhibits good photostability in comparison to other pentacene derivatives and it can be further functionalized by Pd-catalyzed coupling reactions to give a series of soluble and stable functional pentacenes.

H-shaped oligothiophenes with low band gaps and amphoteric redox properties.

H-shaped bridged oligothiophenes HT-1 and HT-2 were synthesized by two different approaches. Different from normal oligothiophenes, HT-1 and HT-2 showed low band gaps and amphoteric redox behaviors due to intramolecular charge transfer, which is further supported by time-dependent DFT calculations.

Fused bispentacenequinone and its unexpected Michael addition.

Fused bispentacenequinone 2 was synthesized by photocyclization of bispentacenequinone 1. Unusual regioselective Michael addition was observed for 2 when excess aryl Grignard reagent was used. Subsequent acidification and oxidation in air gave diaryl-substituted bispentacenequinone 3.

A stable heptacene derivative substituted with electron-deficient trifluoromethylphenyl and triisopropylsilylethynyl groups.

A heptacene derivative 1 substituted with four electron-deficient trifluoromethylphenyl and two triisopropylsilylethynyl (TIPSE) groups was prepared by a new synthetic strategy. Photo-oxidative resistance studies showed that this newly developed heptacene compound persisted 47 h in solution under ambient light and air conditions, and it represents the most stable heptacene derivative reported to date.

Electron-deficient triphenylene and trinaphthylene carboximides.

A series of triphenylene and trinaphthylene carboximides were synthesized mainly through Diels-Alder reactions between the in situ generated radialenes and N-alkylmaleimides. High electron affinity was obtained due to the attachment of electron-withdrawing carboximide groups. These disklike molecules can assemble into one-dimensional columnar structures in solid state and their mesophase properties were characterized by DSC, POM, and X-ray diffraction.