Modern Raman Spectroscopy: A Practical Approach

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Design Of Integrated Circuits For Optical Communications

Preface. Acknowledgments. Abbreviations and Acronyms. Introductory Remarks. A. Group-VI Semiconductors. B. III-V Binary Semiconductors. C. III-V Alloy Semiconductors. D. II-VI Semiconductors. E. IV-VI Semiconductors. F. Amorphous Semiconductors. Index.

Optical constants of crystalline and amorphous semiconductors : numerical data and graphical information

Evolution of Electrospun Nanofibers Fluorescent and Colorimetric Sensors for Environmental Toxicants, pH, Temperature, and Cancer Cells – A Review with Insights on Applications

Highly sensitive ammonia sensors for environmental monitoring are presented. The sensing materials are based on fluorescent BF2-chelated tetraarylazadipyrromethene dyes (aza-BODIPYs) dyes physically entrapped in polyurethane hydrogels and dispersed in silicone rubber. This layer is covered by a hydrophobic porous Teflon membrane used as an additional proton barrier and light scattering layer. The dual-lifetime referenced (DLR) sensors make use of near-infrared (NIR)-emitting Egyptian blue as a reference material and in combination with optical fibers are read-out via a compact phase-fluorometer. The detectable concentration range can be tuned by the choice of aza-BODIPY dye or/and the hydrogel matrix. The most sensitive sensor has a limit of detection (LOD) of 0.11 μg/L and the upper detectable concentration of 300 μg/L. No cross-sensitivity toward pH is observed. The sensors show remarkable operational stability with no noticeable drift over a period of 2 weeks.

Trace Ammonia Sensors Based on Fluorescent Near-Infrared-Emitting aza-BODIPY Dyes

Thermal stability of SiC Schottky diode anode and cathode metalisations after 1000 h at 350 °C

A low-cost multispectral imager was built using a multiwavelength LED PCB (light-emitting diode printed circuit board), 3D printed housing, and a monochrome camera, and it was controlled via Nation...

Low-Cost Multispectral Imager

In this work, a low cost optical pH sensing system that allows for small volume sample measurements was developed. The system operates without the requirement of laboratory instruments (e.g. laser source, spectrometer and CCD camera), this lowers the cost and enhances the portability. In the system, an optical arrangement employing a dichroic filter was used which allows the excitation and emission light to be transmitted using a single fibre thus improving the collection efficiency of the fluorescence signal and also the ability of inserting measurement. The pH sensor in the system uses bromocresol purple as the indicator which is immobilised by sol-gel technology through a dip-coating process. The sensor material was coated on the tip of a 1 mm diameter optical fibre which makes it possible for inserting into very small volume samples to measure the pH. In the system, a LED with a peak emission wavelength of 465 nm is used as the light source and a silicon photo-detector is used to detect the uorescence signal. Optical filters are applied after the LED and in front of the photo-detector to separate the excitation and emission light. The fluorescence signal collected is transferred to a PC through a DAQ and processed by a Labview-based graphic-user-interface (GUI). Experimental results show that the system is capable of sensing pH values from 5.3 to 8.7 with a linear response of R 2 =0.969. Results also show that the response times for a pH changes from 5.3 to 8.7 is approximately 150 s and for a 0.5 pH changes is approximately 50 s.

A pH sensing system using fluorescence-based fibre optical sensor capable of small volume sample measurement

An auto-gain control transimpedence amplifier (TIA) system has been developed in this work for optical sensing applications. In the design, a digitally controlled variable resistor is implemented in the TIA as the feedback resistance (gain) which is controlled by a micro-controller (μC) based board. The μC is programmed to monitor the TIA output and automatically adjust the gain in the TIA to keep the TIA output stable. This avoids signal saturation due to a large input photocurrent or a high ambient environmental condition and stabilize the TIA performance. In addition, the μC allows for a serial interface to a PC that enable the real time process analysis using a graphic user interface (GUI) developed in LabVIEW. With the GUI, the real time TIA gain and the voltage signal at the TIA output can be recorded which makes it easier for the calculation of the incident light's intensity and enhances the system's usefulness in the applications where the intensity measurement is required. Experimental results show that for the gain range up to 255 kΩ, the system developed is capable of automatically adjusting the TIA gain for the changes of incident light to stabilize the TIA performance. In addition, by recording the gain and output signal of the TIA using the PC, the real time photocurrent can be accurately calculated.

Design of an auto-gain control transimpedance amplifier for optical sensing applications

Transparent polymer delivery devices often contain a solid lubricant coating on a stronger bulk polymer. The distribution of lubricant coating must be monitored for device optimisation appraisals and to ensure consistency during mass production. However, coating evaluation is difficult to perform as surfaces are often concealed and/or disjointed. Dye stain analysis, which is destructive and time-consuming, is the current industry standard. We present a prototype IR transmission microscope to evaluate micron-level coating coverage of polyurethane and/or polyvinylpyrrolidone on a poly(propylene)-based delivery device. The device has a common industrial configuration, containing a duct and bevel. Inferred absorption of the coating was used to identify coating coverage and a multivariate analysis was used to remove the effects of absorption and scattering by the bulk. Coverage on concealed and disjointed surfaces was imaged and evaluated from a single camera viewpoint and ≈50 μm defects were detectable. The industrial applicability of the prototype was demonstrated using comparisons with dye stain analysis by estimating water dilution of coating and identifying artifacts in coating, which may indicate machine malfunction. The sensitivity and speed of the IR technique makes it a favourable alternative to the current industry standard.

https://www.mdpi.com/1424-8220/20/22/6408/pdf

Liam Lewis

Papers

Thermal stability of SiC Schottky diode anode and cathode metalisations after 1000 h at 350 °C

Low-Cost Multispectral Imager

A pH sensing system using fluorescence-based fibre optical sensor capable of small volume sample measurement

Design of an auto-gain control transimpedance amplifier for optical sensing applications

IR Imaging of Solid Lubricant Coatings on Concealed/Disjointed Surfaces for Transparent Polymer Delivery Device Applications