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.

Highly sensitive NH3 sensor using Pt catalyzed silica coating over WO3 thick films

Abstract: Ammonia gas sensing properties of a single layer WO 3 thick film and a double layer sensor structure having a supported catalyst on it have been investigated. The single layer sensor exhibited low response to NH 3 . An enhancement in gas response was achieved by doping WO 3 with Pt, Pd or Au. Ammonia sensing properties of the WO 3 thick film was improved markedly by overcoating a platinum catalyzed silica-niobia layer onto the WO 3 film surface. Such a double layer structure not only increased the gas response, but decreased the response time also.

Estimation of inelastic mean free paths for polymers and other organic materials - use of quantitative structure-property relationships

Abstract: Inelastic mean free path values are needed for quantitative XPS analysis of a range of important polymers and other organic materials. Measured reference data are limited, although some semi-empirical equations to estimate IMFP are available. Existing estimation methods often require values for such quantities as the bandgap (in electron-volts) or the density, for which accurate measurements may not be available. Here we develop a scheme for estimation of the IMFP that can be applied across a range of organic structures for kinetic energies of ∼200–2000 eV. This involves a quantitative structure–property relationship (QSPR), which allows the IMFP to be estimated for any organic material from its structural formula alone, either via a straightforward calculation on paper or instantly using one of a number of commercial molecular-modelling software packages. The accuracy of this IMFP estimate is better than existing methods, such as the TPP-2M equation for organic materials. In the majority of analytical problems involving surface analysis in chemistry or biochemistry, the structural formula of the organic material is known or can be conjectured with reasonable confidence, so that the approach described here is more widely applicable in practise and likely to be more accurate than previous methods for estimating the IMFP in organic materials. © Crown Copyright 2001 Reproduced by permission of the Controller of HMSO.

Application of conducting polyaniline as sensor material for ammonia

Abstract: The change in resistance of polyaniline on exposure to aqueous ammonia has been utilized for the study of a prototype chemical sensor. This paper discusses various aspects of polyaniline and its suitability as a chemical sensor, particularly with reference to aqueous ammonia solution.

Aerosols over Delhi during pre‐monsoon months: Characteristics and effects on surface radiation forcing

Abstract: [1] The surface fluxes in the wavelength range 280-2800 nm were measured during the pre-monsoon period, April-June 2003 along with the spectral distribution of aerosol optical depth (AOD) in the visible and near infrared wavelengths. The Angstrom exponent alpha retrieved from the data showed abundance of desert aerosols over Delhi during this period. The aerosol composition constructed using the OPAC model indicated a typical mixture of two aerosol types: urban and desert. Due to this the aerosol mixture had a very low value of single scattering albedo ∼0.67. The average total radiative forcing efficiency observed at the surface in the broad wavelength band (280-2800 nm) was estimated and compared with the SBDART model calculated values. Citation: Singh, S., S. Nath, R. Kohli, and R. Singh (2005), Aerosols over Delhi during pre-monsoon months: Characteristics and effects on surface radiation forcing.