DNA nanotechnology and particularly DNA origami, in which long, single-stranded DNA molecules are folded into predetermined shapes, can be used to form complex self-assembled nanostructures. Although DNA itself has limited chemical, optical or electronic functionality, DNA nanostructures can serve as templates for building materials with new functional properties. Relatively large nanocomponents such as nanoparticles and biomolecules can also be integrated into DNA nanostructures and imaged. Here, we show that chemical reactions with single molecules can be performed and imaged at a local position on a DNA origami scaffold by atomic force microscopy. The high yields and chemoselectivities of successive cleavage and bond-forming reactions observed in these experiments demonstrate the feasibility of post-assembly chemical modification of DNA nanostructures and their potential use as locally addressable solid supports.

Chemiresistive sensors are becoming increasingly important as they offer an inexpensive option to conventional analytical instrumentation, they can be readily integrated into electronic devices, and they have low power requirements. Nanowires (NWs) are a major theme in chemosensor development. High surface area, interwire junctions, and restricted conduction pathways give intrinsically high sensitivity and new mechanisms to transduce the binding or action of analytes. This Review details the status of NW chemosensors with selected examples from the literature. We begin by proposing a principle for understanding electrical transport and transduction mechanisms in NW sensors. Next, we offer the reader a review of device performance parameters. Then, we consider the different NW types followed by a summary of NW assembly and different device platform architectures. Subsequently, we discuss NW functionalization strategies. Finally, we propose future developments in NW sensing to address selectivity, sensor drift, sensitivity, response analysis, and emerging applications.

Chemical sensing is of critical importance to human health, safety, and security, yet it is not broadly implemented because existing sensors often require trained personnel, expensive and bulky equipment, and have large power requirements. This study reports the development of a smartphone-based sensing strategy that employs chemiresponsive nanomaterials integrated into the circuitry of commercial near-field communication tags to achieve non-line-of-sight, portable, and inexpensive detection and discrimination of gas-phase chemicals (e.g., ammonia, hydrogen peroxide, cyclohexanone, and water) at part-per-thousand and part-per-million concentrations.RFID | NFC | sensor | nanomaterials | wireless P ortable chemical sensors are needed to manage and protect the environment (1), human health (2, 3), and quality of life (4). Examples include sensors for point-of-care diagnosis of disease (5), detection of explosives and chemical warfare agents (6), indication of food ripening and spoilage (7), and monitoring of environmental pollution (1). Connecting sensors with information technology through wireless rf communication is a promising approach to enable cost-effective onsite chemical detection and analysis (8). Although rf technology has been recently applied toward wireless chemical sensing, current approaches have several limitations, including lack of specificity to selected chemical analytes, requirements for expensive, bulky, fragile, and operationally complex impedance and network analyzers, and reliance on extensive data processing and analysis (8-13). We report herein the adaptation of a nascent technology embedded in modern smartphones-near-field communication (NFC)-for wireless electronic, portable, non-line-of-sight selective detection of gasphase chemicals ( Fig. 1 and Fig. S1). We demonstrate this concept by (i) incorporating carbon-based chemiresponsive materials into the electronic circuitry of commercial NFC tags by mechanical drawing and (ii) using an NFC-enabled smartphone to relay information regarding the chemical environment (e.g., presence or absence of a chemical) surrounding the NFC tag. This paper illustrates the ability to detect and differentiate partper-million (ppm) concentrations of ammonia, cyclohexanone, and hydrogen peroxide. We demonstrate the ability to couple wireless acquisition and transduction of chemical information with existing smartphone functions [e.g., Global Positioning System (GPS)] (Movie S1).Many commercial smartphones and mobile devices are equipped with NFC hardware configured to communicate wirelessly with NFC "tags"-simple electrical resonant circuits comprising inductive (L), capacitive (C), and resistive (R) elements on a plastic substrate (Fig. 1). The smartphone, such as the Samsung Galaxy S4 (SGS4) used in this study, communicates with the battery-free tag by powering its integrated circuit (IC) via inductive coupling at 13.56 MHz (14). Power transferred from the smartphone to the IC is, among other variables, a function of the transmission frequency (f), the re...

We report a simple, rapid and solvent-free methodology for solid-state polymerizations yielding poly(phenylene vinylenes) (PPV) promoted by ball-milling. This solid-state Gilch polymerization method produces PPVs in as little as five minutes of milling. Detailed investigations of the parameter space governing the solid-state polymerization, i.e. milling time, base strength, solid-state dilution, milling frequency and size of milling balls, revealed that polymerization by ball-milling is a rapid process achieving molecular number average weights of up to 40 kDa in up to 70% yield. To explore the scope, a solid-state polymerization via the dithiocarbamate precursor route is explored.