National Physical Laboratory

About: National Physical Laboratory is a facility organization based out in London, United Kingdom. It is known for research contribution in the topics: Dielectric & Thin film. The organization has 7615 authors who have published 13327 publications receiving 319381 citations.

Quantitative AES and XPS: Determination of the electron spectrometer transmission function and the detector sensitivity energy dependencies for the production of true electron emission spectra in AES and XPS†

Abstract: For the use of published general or theoretical sensitivity factors in quantitative AES and XPS, the energy dependence of both the spectrometer transmission function and the detector sensitivity must be known. Here, we develop simple procedures that allow these dependencies to be determined experimentally. Detailed measurements for a modified VG Scientific ESCALAB II, the metrology spectrometer, operated in both the constant ΔE/E and constant ΔE modes, are presented and compared with theoretical estimates. It is shown that an exceptionally detailed electron-optical calculation, involving proprietary information, would be required to match the accuracy of the experimental procedures developed. Removal of the spectrometer transmission function and the detector sensitivity terms allow the measured spectrum to be converted to the true electron emission spectrum, irrespective of the mode of operation. This provides the first step to the provision of reference samples to calibrate the transmission functions and detector sensitivities of all instruments so that they, in turn, may produce true electron emission spectra. This is vital if: (1) all instruments are to give consistent results; (2) theoretical terms are to be used in quantifying either AES or XPS; (3) reference data banks are to be established for AES or XPS.

Nanostructured cerium oxide film for triglyceride sensor

Abstract: Lipase has been immobilized onto sol gel derived nanostuctured cerium oxide (Nano-CeO 2 , 35nm)“lm deposited onto indium tin oxide (ITO) coated glass plate for tributyrin detection. The Nano-CeO 2 /ITO electrode and lipase/nano-CeO 2 /ITO bioelectrode have been characterized using scanningelectron microscopy (SEM) and cyclic voltammetry (CV). The electrochemical response of lipase/nano-CeO 2 /ITO bioelectrode towards tributyrin, investigated using CV studies, exhibits linearity, detectionlimit and shelf life as 50 500mg/dL, 32.8mg/dL and 12 weeks, respectively. The value of the apparentMichaelis Menten constant ( K appm ) obtained as 22.27mg/dL (0.736mM) for lipase/nano-CeO 2 /ITO bio-electrode indicates high af“nity of lipase with tributyrin. Attempts have been made to detect triglycerideconcentration in serum samples.© 2009 Elsevier B.V. All rights reserved. 1. IntroductionEstimation of triglycerides (triacylglycerols) is extremelyimportant since its high concentration [normal range in men(40 160mg/dl) and in women (35 135mg/dl)] can cause hyper-lipidemia [1 3] . Apart from coronary diseases, hyperlipidemiais associated with several disorders including diabetes mellitus,nephrosis, liver obstruction and endocrine. Moreover, estimationof triglycerides content in food has become important due toincreased health awareness and stringent regulatory laws [4]. Theconventionalmethodsfortriglyceridesdetectionsuchascolorimet-ricor”uorometrictechniquesarebasedonenzymatichydrolysisoftriglycerides to glycerol and free fatty acids [5 7] .Most triglyceride biosensors reported till date are based onmulti-enzymes wherein a biochemical reaction depends uponenzyme kinetics of the other enzymatic reaction. McGowan etal. have described an enzymatic method for serum triglyceridedetection that involves simultaneous catalysis of four bio-enzymes(lipase, glycerol kinase, l-a-glycerophosphate oxidase and per-oxidase) [8]. These methods are, however, time-consuming,complicated and expensive. Basu et al. have recently fabricated apH-based biosensor for triglycerides detection using silicon and anelectrolyte insulator semiconductor capacitor (EISCAP) [9]. Microreactor packed with immobilized lipase has been used for triglyc-eride detection using ion sensitive “eld effective transistor (ISFET)