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Optical methods for modulating cellular behavior are promising for both fundamental and clinical applications. However, most available methods are either mechanically invasive, require genetic manipulation of target cells, or cannot provide sub-cellular specificity. Here, we address all these issues by showing optical neuromodulation with free-standing coaxial p-type/intrinsic/n-type silicon nanowires. We revealed the presence of atomic gold on the nanowire surfaces, likely due to gold diffusion during the material growth. To evaluate how surface gold impacts the photoelectrochemical properties of single nanowires, we used modified quartz pipettes from a patch clamp and recorded sustained cathodic photocurrents from single nanowires. We show that these currents can elicit action potentials in primary rat dorsal root ganglion neurons through a primarily atomic gold-enhanced photoelectrochemical process.

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We report ZnO nanorod-graphene hybrid architectures (ZnO-G HAs) composed of regular arrays of ZnO nanorods formed on few-layer graphene films transferred to transparent and/or flexible substrates. The ZnO-G HAs exhibited a high current flow reaching ∼1.1 mA at an applied bias of 1 V and good optical transmittance in the range of 70-80%, comparable to those of a graphene layer. In addition, cathodoluminescence images and photoluminescence spectra of the ZnO-G HAs showed distinct light emission involving optical transitions in the ZnO nanorod array. Moreover, a bending test demonstrated that the ZnO-G HAs exhibit excellent mechanical flexibility and structural stability for the bending radius down to ∼4 mm. Our results suggest that the 1D-2D HAs provide unique and multiple functions as can be applicable for next-generation electronic and optoelectronic systems.

Nucleic acid amplification techniques have been among the most powerful tools for biological and biomedical research, and the vast majority of the bioassays rely on thermocycling that uses time-consuming and expensive Peltier-block heating. Here, we introduce a plasmonic photothermal method for quantitative real-time PCR, using gold bipyramids and light to achieve ultrafast thermocycling. Moreover, we successfully extend our photothermal system to other biological assays, such as isothermal nucleic acid amplification and restriction enzyme digestion.

We report a type of device that combines vertical arrays of one-dimensional (1D) pillar-superlattice (PSL) structures with 2D graphene sheets to yield a class of light emitting diode (LED) with interesting mechanical, optical, and electrical characteristics. In this application, graphene sheets coated with very thin metal layers exhibit good mechanical and electrical properties and an ability to mount, in a freely suspended configuration, on the PSL arrays as a top window electrode. Optical characterization demonstrates that graphene exhibits excellent optical transparency even after deposition of the thin metal films. Thermal annealing of the graphene/metal (Gr/M) contact to the GaAs decreases the contact resistance, to provide enhanced carrier injection. The resulting PSL-Gr/M LEDs exhibit bright light emission over large areas. The result suggests the utility of graphene-based materials as electrodes in devices with unusual, nonplanar 3D architectures.

Nat. Acad. Sci. US 112 (2015) 5407). The effect of the metal ions can be followed by bulk fluorescence measurements as well as by FCS.

Engineered silicon-based materials can display photoelectric and photothermal responses under light illumination, which may lead to further innovations at the silicon-biology interfaces. Silicon nanowires have small radial dimensions, promising as highly localized cellular modulators, however the single crystalline form typically has limited photothermal efficacy due to the poor light absorption and fast heat dissipation. In this work, we report strategies to improve the photothermal response from silicon nanowires by introducing nanoscale textures on the surface and in the bulk. We next demonstrate high-resolution extracellular modulation of calcium dynamics in a number of mammalian cells including glial cells, neurons, and cancer cells. The new materials may be broadly used in probing and modulating electrical and chemical signals at the subcellular length scale, which is currently a challenge in the field of electrophysiology or cellular engineering.