Carbon Nanotube–Polymer Composites: Device Properties and Photovoltaic Applications

This chapter provides an in-depth coverage of recent advances in the areas of the development and characterization of electro-optically active, device-grade carbon nanotube (CNT)–polymer blends. These new organic–inorganic multifunctional nanocomposites share many advanced characteristics which make them ideally suited for industrial scale, high-throughput manufacturing of lightweight, flexible electronic, light switching and emitting as well as energy harvesting devices of extremely low cost. The fundamental aspects and the physical mechanisms controlling light–matter interaction, photo-conversion, and photo-generated charge-carrier transport in these nanotube–polymer composites as well as the influence of the processing conditions on the electronic properties and device-related performances are further reviewed and discussed

Room-temperature single-electron charging in electrochemically synthesized semiconductor quantum dot and wire array

Cylindrical quantum dots of diameter ∼8 nm and height 3–10 nm, and wires of diameter 50 nm and height 500–1000 nm, were self-assembled by electrodepositing semiconductors in the nanometer-sized pores of anodic alumina films. Current–voltage characteristics of both wires and dots show Coulomb blockade at room temperature, while the wires also show a Coulomb staircase when exposed to infrared radiation. These results establish that electrochemicalself-assembly is a viable technique for producing nanostructures that have potential uses in room-temperature single electronics

Transient reflectance of photoexcited Cd\u3csub\u3e3\u3c/sub\u3eAs\u3csub\u3e2\u3c/sub\u3e

We report ultrafast transient-grating measurements of crystals of the three-dimensional Dirac semimetal cadmium arsenide, Cd3As2, at both room temperature and 80 K. After photoexcitation with 1.5-eV photons, charge-carriers relax by two processes, one of duration 500 fs and the other of duration 3.1 ps. By measuring the complex phase of the change in reflectance, we determine that the faster signal corresponds to a decrease in absorption, and the slower signal to a decrease in the light\u27s phase velocity, at the probe energy. We attribute these signals to electrons\u27 filling of phase space, first near the photon energy and later at lower energy. We attribute their decay to cooling by rapid emission of optical phonons, then slower emission of acoustic phonons. We also present evidence that both the electrons and the lattice are strongly heated

Controlling opto-electronic characteristics of ternary II–VI alloyed quantum dots: alcohol processing assay

For their ultra-wide color gamut, high efficiency, robustness, and solution processability, Cd-based alloy semiconductor quantum dots (AQDs) continue to proliferate by driving innovations in the fields of optoelectronics, photovoltaics, multiplex bio-imaging, and cancer research. Herein, non-toxic, low-cost isopropyl alcohol vapor-based oxidative treatment protocol is developed and applied to tune the light emission spectrum of crystalline core–shell CdSe1−xSx/ZnS quantum dots. As evidenced by the results of structural investigations, these AQDs when exposed to vapors produced ultrasonically from 10:1 isopropyl alcohol-to-water mix undergo an isotropic, diameter non-specific size reduction at the rate of∼1.3 Å min−1. Nonlinear time-dependent spectral shifts, revealed experimentally, are consistent with the results of the effective-mass approximation treatment. The emission yields are seen to undergo an initial drop, yet to plateau as the etch time increases. The study opens a door to a soft, top-down monotonic tailoring of the light emission characteristics and opto-electronic response of stoichiometrically- and hierarchically-complex core–shell constructs in technologically-viable group II–VI nano-semiconductors as well as AQD-based catalytic conversion of organic compound

Room-temperature self-powered energy photodetector based on optically induced Seebeck effect in Cd\u3csub\u3e3\u3c/sub\u3eAs\u3csub\u3e2\u3c/sub\u3e

We demonstrate an intrinsically fast Seebeck-type metal–semimetal–metal infrared photodetector based on Cd3As2 crystals. The Seebeck voltage is induced under off-center illumination, leading to asymmetric temperature gradients and a net current flow. The room-temperature responsivity of the sensor is 0.27 mA/W. The photocurrent signal is readily registered at a modulation frequency of 6 kHz, and the intrinsic bandwidth of the sensor is predicted to approach the terahertz range. The photocurrent depends on the optical power and modulation frequency. Our study demonstrates that crystallineCd3As2 is a promising material for high-bandwidth and spectrally broad photosensing, imaging, and communication

Enhanced UV Light-Emission of Zinc-Phosphate-Hydrate Hydrothermally-Grown on Cu Metal Substrates for Opto-Electronic Applications

In the present study, polycrystalline films of layered zinc phosphate hydrate are produced by a facile, low-temperature single-step hydrothermal fabrication method on top of Cu metal substrates. Despite containing structural water, the as-grown films remain crystalline, chemically stable, and electrically conductive. The photoluminescence spectrum obtained at room-temperature reveals the presence of a spectrally narrow, high-intensity ultraviolet band that consists of two Gaussian peaks at ≈377 and 383 nm and a UV-to-visible peak emission intensity ratio of ≈5.3. The electrical charge-transport properties remain Ohmic for electric fields of up to ≈2 kV m−1 and temperature (T) range of ≈223–368 K. The electrical conductivity is further found to vary exponentially with the inverse temperature, and the thermal activation energy, Ea is 285 ± 8 meV. A moderate UV-vis photoconduction effect is registered and assigned to light-assisted electronic transitions that involve near-band edge defect states. This study can potentially open a door to the engineering and deployment of water-based compounds with advanced, semiconducting-like attributes in short-wavelength opto-electronic devices

A Miniature Probe for Ultrasonic Penetration of a Single Cell

Although ultrasound cavitation must be avoided for safe diagnostic applications, the ability of ultrasound to disrupt cell membranes has taken on increasing significance as a method to facilitate drug and gene delivery. A new ultrasonic resonance driving method is introduced to penetrate rigid wall plant cells or oocytes with springy cell membranes. When a reasonable design is created, ultrasound can gather energy and increase the amplitude factor. Ultrasonic penetration enables exogenous materials to enter cells without damaging them by utilizing instant acceleration. This paper seeks to develop a miniature ultrasonic probe experiment system for cell penetration. A miniature ultrasonic probe is designed and optimized using the Precise Four Terminal Network Method and Finite Element Method (FEM) and an ultrasonic generator to drive the probe is designed. The system was able to successfully puncture a single fish cell

Surface patterning of carbon nanotubes can enhance their penetration through a phospholipid bilayer

Nanotube patterning may occur naturally upon the spontaneous self-assembly of biomolecules onto the surface of single-walled carbon nanotubes (SWNTs). It results in periodically alternating bands of surface properties, ranging from relatively hydrophilic to hydrophobic, along the axis of the nanotube. Single Chain Mean Field (SCMF) theory has been used to estimate the free energy of systems in which a surface patterned nanotube penetrates a phospholipid bilayer. In contrast to un-patterned nanotubes with uniform surface properties, certain patterned nanotubes have been identified that display a relatively low and approximately constant system free energy (10 kT) as the nanotube traverses through the bilayer. These observations support the hypothesis that the spontaneous self-assembly of bio-molecules on the surface of SWNTs may facilitate nanotube transduction through cell membranes.Comment: Published in ACS Nano http://pubs.acs.org/doi/abs/10.1021/nn102763

Single spin measurement in the solid state: a reader for a spin qubit

We describe a paradigm for measuring a single electron spin in a solid. This is a fundamental problem in condensed matter physics. The technique can be used to read a spin qubit relatively non-invasively in either a spintronic quantum gate or a spintronic quantum memory. The spin reader can be self assembled by simple electrochemical techniques and can be integrated with a quantum gate.Comment: 10 pages of text, 4 figure