Photocatalytic oxidative disinfection (POD) towards pathogenic bacteria has become a popular approach in public health due to its environmentally friendly antimicrobial capabilities. However, this approach is still limited by inherent fast electron-hole recombination within photocatalysts and poor interactions between bacterial cells and photogenerated reactive oxygen species (ROS) at the biointerface. Particularly, those ROS with extremely short migration distances cannot reach the bacterial cells before they deteriorate into less potent or neutral species, resulting in reduced antibacterial activities. By far, these phenomena are still poorly understood. Inspired by the fact that bacterial cells are negatively charged, we rationally designed a photocatalyst (i.e., g-C3N4/MIL-125-NH2) by coating a layer of positively charged quaternary ammonium compound (QAC) polymer onto the surface to enhance its affinity towards bacterial cells via electrostatic attractions. This surface-modulated photocatalyst is denoted as QAC@g-C3N4/MIL-125-NH2. The visualization and quantification of the electrostatic interactions between the bacterial cells and the QAC@g-C3N4/MIL-125-NH2 photocatalyst were conducted using a confocal laser scanning microscope and atomic force microscope, respectively. The results showed that the positively charged QAC layer did promote the bacteria-photocatalyst contact via electrostatic attractions. Due to the cooperative effects of bacterial cell adhesion and ROS generation, the POD performance of the photocatalyst is significantly enhanced. Notably, the photocatalyst achieves 3.20 logs of inactivation efficiency for Staphylococcus epidermidis within 60 min under visible light irradiation. This work provides insights into a mechanistic understanding of bacterial adhesion and disinfection at the biointerface and sheds light on rational photocatalyst design with surface charge modulation for antibacterial applications.

Wearable biosensors for continuous health monitoring, particularly those used for glucose detection, have a limited operational lifetime due to biodegradation and fouling. As a result, patients must change sensors frequently, increasing cost and patient discomfort. Arrays of multiple sensors, where the individual devices can be activated on demand, increase overall operational longevity, thereby reducing cost and improving patient outcomes. This work demonstrates the feasibility of this approach via decomposition of combustible nitrocellulose membranes that protect the individual sensors from exposure to bioanalytes using a current pulse. Metal contacts, connected by graphene-loaded PEDOT:PSS polymer on the surface of the membrane, deliver the required energy to decompose the membrane. Nitrocellulose membranes with a thickness of less than 1 µm consistently transfer on to polydimethylsiloxane (PDMS) wells. An electrical energy as low as 68 mJ has been shown to suffice for membrane decomposition.

Crystallization of CH3NH3PbI3 perovskite films was performed in supercritical carbon dioxide with and without organic cosolvents. Post deposition crystallization of the films was performed in a binary, single phase supercritical fluid at constant conditions (45 degrees, 1200 psi) but with varying cosolvent volume fractions up to 2 %. Organic cosolvents with varying polarity, propensity for hydrogen bonding and strength of solvation were used and the resulting perovskite film morphology, crystal structure and optical absorption spectra were measured. It was determined that the cosolvents can provide selective interactions with one or both of the perovskite precursor compounds resulting in different film morphologies ranging from uniform films containing large grains to films exhibiting large cubic or hexagonal crystals or preferential crystallographic orientations. The use of supercritical fluids to enhance or tune crystallization in solid-state thin films could have broad applications toward the realization of high efficiency photovoltaic devices. (C) 2019 Elsevier B.V. All rights reserved.

We report on a commercial laser system based on a Yb fiber oscillator with cross-filter mode lock (CFML) mechanism that is integrated with a programmable pulse shaper. The laser is self-starting and stable in a wide temperature range, 15- 50°C, resilient to vibrations and shock. It can serve as a seed for high-power femto- and pico- second systems or be implemented as a standalone unit, as illustrated in this paper. The master oscillator is outputting strongly chirped pulses, with the spectrum centered at 1030 nm and having the full bandwidth of up to 90 nm. It operates at 11 MHz repetition rate, with the pulse energy of at least 10 nJ at the output. When equipped with an additional power amplification module, the oscillator yields the same spectral output and repetition rate, but the pulse energy can be increased up to 400 nJ. The laser output is fully coherent, and pulses are compressible down to the transform limit (TL). For demanding femtosecond applications, the laser system is being configured with a static grating compressor and a compact spectral phase shaper. The pulse shaper utilizes a liquid-crystal spatial light modulator for active phase control which enables high-finesse pulse compression as well as arbitrary manipulation of the pulse waveform. With the use of the pulse shaper, the oscillator output is compressed down to 57 fs, which is within 7% from the TL pulse duration, 53 fs, calculated from the experimental laser spectrum.

We report on industrial-grade femtosecond Yb fiber lasers with >100μJ pulse energy and <300fs pulse duration using a tunable all-fiber pulse shaper. The rugged, compact phase modulator is a lossless addition to the standard chirped-pulseamplification scheme. The automated multichannel phase control across the optical bandwidth enables generation of near transform-limited pulses at the laser output, improves unit-to-unit reproducibility of laser pulse characteristics, and reduces laser build time.

Traditionally, handmade gold jewelry played a very important role in the cultural heritage of Bangladesh. Goldsmiths still are partially using ancient manufacturing process with coal fire, candle flame blowing, and nitric and sulfuric acid treatments. Such process leads to the contamination of workplace with the dust of toxic metals, acidic vapors, and particles of different natures. To evaluate contamination by particulate matter (PM), the passive particle collectors were installed in different manufacturing units for a period of 85 days at Tanti Bazar, Dhaka, Bangladesh. The laser diffraction analysis of the samples collected at the soldering units showed significant amounts of particulates, both PM10 and PM 2.5, and also nanoparticles in both nucleation and accumulation mode. SEM/EDS analysis revealed partially melted micro blebs that contain a very high concentration of Fe along with Cu. The toxic elements were detected with ICP analysis and include higher concentrations of cadmium (Cd), chromium (Cr), lead (Pb), and arsenic (As). It is notable that detection of arsenic contamination was unexpected since raw materials used for jewelry making should not have any arsenic.

We examine the concentration dependence of the Coherent Anti-Stokes Raman Scattering (CARS) signal obtained for gas mixtures at various conditions using the Femtosecond Adaptive Spectroscopic Technique (FAST). We use the CARS signal of the Q-branch vibrational oscillation of molecular oxygen (1556 cm−1) to confirm the quadratic dependence of the coherent signal on the number of molecules in a test volume. In addition, we demonstrate multi-shot FAST CARS imaging of a gas flow in free space by raster-scanning the area of interest.

The authors present a new low-temperature nanowire fabrication process that allows high-aspect ratio nanowires to be readily integrated with microelectronic devices for sensor applications. This process relies on a new method of forming a close-packed array of self-assembled high-aspect-ratio nanopores in an anodized aluminum oxide (AAO) template in a thin (2.5 μm) aluminum film deposited on a silicon substrate. This technique is in sharp contrast to the traditional free-standing thick film methods, and the use of an integrated thin aluminum film greatly enhances the utility of such methods. The authors have demonstrated the method by integrating ZnO nanowires onto the metal gate of a metal-oxide-semiconductor (MOS) transistor to form an integrated chemical field-effect transistor (ChemFET) sensor structure. The novel thin film AAO process uses a novel multistage aluminum anodization, alumina barrier layer removal, ZnO atomic layer deposition (ALD), and pH controlled wet release etching. This new process selectively forms the ZnO nanowires on the aluminum gate of the transistor while maintaining the remainder of the aluminum film intact for other integrated device components and interconnects. This self-assembled high-density AAO template was selectively formed in an ultrasmooth 2.5 μm thick aluminum layer deposited through e-beam evaporation without the electropolishing required in AAO template formation in traditional 100 μm thick free standing films. The resulting nanopore AAO template consists of nanopores of 90 nm in diameter and 1 μm in height at an aerial density of 1.3 × 1010 nanopores/cm2. This thin film AAO template was then filled with ZnO using ALD at 200 °C, forming polycrystalline ZnO nanowires inside the pores. The alumina template was then removed with a buffered NaOH solution, leaving free standing ZnO nanowires of 1 μm height and 90 nm diameter, offering an increase in 38× the surface area over a standard flat ZnO film for sensing applications. The aluminum film remains intact (unanodized) in nonselected regions of the device as well as underlying the ZnO nanowires, acting as the gate of the MOS transistor. The ZnO nanowires were characterized by scanning electron microscopy, energy-dispersive x-ray spectroscopy, and transmission electron microscopy to verify stoichiometry and crystal structure. Additionally, the response of a ZnO nanowire ChemFET was measured using ammonia as a target gas. I-V characterization and transient response to ammonia in the range of 25–200 ppm were examined. The ammonia response to the threshold limit value concentration of ammonia (25 ppm) shows a 56 mV shift in threshold voltage, an overall sensitivity of 14%, an 8 min response time, and a 27 min recovery period. The ZnO nanowire fabrication sequence that the authors present is accomplished at low-temperature (<200 °C) and can be accomplished selectively, making it readily amenable to integration with standard metal-oxide-semiconductor field-effect transistor processing as well as other microelectronic sensors such as surface acoustic wave devices. This new process has initially been demonstrated using ZnO, but is also adaptable to a variety of nanowire materials using appropriate deposition methods as well as selective nanowire release methods. This allows the potential to conveniently fabricate a variety of high-aspect ratio nanowire based microelectronic sensors for a range of applications.

We report on the fabrication and characterization of a Schottky diode made using 2D germanane (hydrogenated germanene). When compared to germanium, the 2D structure has higher electron mobility, an optimal band-gap, and exceptional stability making germanane an outstanding candidate for a variety of opto-electronic devices. One-atom-thick sheets of hydrogenated puckered germanium atoms have been synthesized from a CaGe2 framework via intercalation and characterized by XRD, Raman, and FTIR techniques. The material was then used to fabricate Schottky diodes by suspending the germanane in benzonitrile and drop-casting it onto interdigitated metal electrodes. The devices demonstrate significant rectifying behavior and the outstanding potential of this material.

Nonlinear optical applications depend on pulse duration and coherence of the laser pulses. Characterization of high-repetition rate pulsed laser sources can be complicated by their pulse-to-pulse instabilities. Here, we introduce and demonstrate experimentally a quantitative measurement that can be used to determine the pulse-to-pulse fidelity of ultrafast laser sources. Numerical simulations and experiments illustrate the effect of spectral phase and amplitude noise on second and third harmonic generation.

Di(2-ethylhexyl)phthalate (DEHP) is a commonly employed plasticizer for poly(vinyl chloride) (PVC). Diffusion of di(2-ethylhexyl)phthalate (DEHP) takes place when plasticized PVC is immersed in hexane. Rather than determining DEHP concentration in the immersion solvent, an IR window for PVC from 1500 to 1900 cm(-1) enabled direct measurement of HADD (hexane assisted DEHP diffusion) using ATR-IR by monitoring the DEHP carbonyl absorption at 1715 cm(-1). The present study employed PVC containing 45% plasticizer (PVC-45, tygon tubing). A fast diffusion process was observed for short times (<30 s) while a slower diffusion process occurred at longer immersion times (30 s < t < 6 min). A synergistic increase in mesosurface T-g toward that of PVC coupled with low solubility of hexane in PVC accounts for decreased DEHP diffusion rates (10(-12)-10(-13) cm(2) s(-1)) for immersion times > 30 s. Analysis by XPS shows the outermost surface is PVC free of plasticizer after 6 min immersion. After an induction period, back diffusion coefficients D-b were estimated from peak areas during a subsequent fast recovery period (10(-14) -10(-15) cm(2) sec(-1)). A model is proposed for the induction period associated with re-plasticization that involves a change from a mesosurface glass to a gel like solid. (C) 2015 Elsevier Ltd. All rights reserved.