Abstract The definition of a “primary method measurement ” has permitted full consideration the primary standards for pH, determined by (cell without transference, Harned cell), secondary methods, and question whether as conventional quantity, can be incorporated within internationally accepted system measurement, International System Units (SI, Système d’ Unités). This approach enabled resolution previous compromise IUPAC 1985 Recommendations [ Pure Appl. Chem. 57 , 531 (1985)]....

On 16 November 2018 a revision of the International System Units (the SI) was agreed by General Conference on Weights and Measures. The definitions base units were presented in new format that highlighted link between each unit defined value an associated constant. physical concepts underlying kilogram, ampere, kelvin mole have been changed. definition kilogram is particular importance because it eliminated last referring to artefact. In this way, use rules nature create measurement tie...

Primary methods of measurement play an important role in metrology because they provide the essential first link chain traceability from abstract definition a unit International System Units (SI) to its practical use measurement. A primary method has been developed by Consultative Committee for Amount Substance (CCQM) that distinguishes between those measure quantity directly and ratio two quantities. Methods do not fulfil being also measuring amount substance. In some cases, it is...

Abstract We review the performance of various nanoscaled structures needed to support propagation surface plasmons responsible for surface‐enhanced Raman scattering (SERS), and assess potential optimisation compromise between enhancement reproducibility that they provide, hence their utility relevant applications. divide these nanostructures into those comprising structured arrays discrete nanoparticles in two or three dimensions, regularly patterned surfaces dimensions. The most promising...

This report presents the results of first phase campaign calibration carried out with respect to international prototype kilogram (IPK) in anticipation redefinition (Extraordinary Calibrations). The definition was realized according procedure outlined 8th Edition SI Brochure. Thus IPK and its six official copies have been cleaned washed following BIPM procedure.

Novel insights into the manufacture of nickel–phosphorus black surfaces by chemical etching electroless-deposited Ni–P alloy has been achieved examining influence pre-etch phosphorus composition and method on resulting morphology, reflectance surface produced. An optimum regime to produce low blacks 0.4% or lower in visible region is proposed. Cross-sectional analysis etched allowed, for first time, an accurate determination scale enhanced morphologies produced thickness oxidised layer...

Several aspects of the electromagnetic contribution to surface enhanced Raman scattering (SERS) are revisited and analyzed in terms known concepts ideas field photonic crystals. A qualitative understanding some reported SERS phenomena can be achieved by this analysis complex energy distribution spatial localization plasmon resonances active media. few outstanding issues (like overwhelming success nonresonant excitation) explained within framework and, addition, new physical utilizing...

Abstract There is a pressing need to improve the reproducibility of surface enhanced Raman spectroscopy (SERS) measurements, if technique be used routinely for trace analysis. This particularly true colloidal SERS, in which data dominated by final shape and size metal clusters produced during colloid aggregation. study presents general guidelines designing appropriate measurement strategies that can identify optimise crucial steps protocol leads better results. We show improved optimising...

The most widely used method for the preparation of primary standard gas mixtures involves weighing individual components into a cylinder. We present new mathematical description and its uncertainties. use this to demonstrate how strategies serial dilution can be identified that minimize uncertainty in final mixture show they implemented practically. review published reports high accuracy gravimetry give examples relative uncertainties composition standards approaching 1 part-per-million best...

Abstract In order to fulfil its mission ensure and promote the global comparability of measurements, BIPM operates laboratories in fields physical metrology, ionizing radiation, chemistry time. These act as centres for scientific technical collaboration between Member States providing capabilities international measurement comparisons on a shared cost basis. They coordinate national standards agreed be highest priority, they establish maintain appropriate reference use basis key at level...

The determination of a best-fit calibration curve that describes the response measuring system to value standard is one most widely used procedures in metrology. mathematical basis for generalized least-squares solution this problem reviewed. Examples application software implementation method are presented illustrate treatment problems with different uncertainty structures data, including correlated data. examples concern analysers measure composition natural gas and flow dilutor.

There has been considerable discussion about the merits of redefining four base units SI, including mole. In this paper, options for implementing a new definition mole based on fixed value Avogadro constant are discussed. They placed in context macroscopic nature quantity amount substance and opportunity to introduce system molar atomic masses with unchanged values consistent relative uncertainties.

Engineered gold nanostructured arrays with feature separation in the sub-10-nm range were fabricated and used for highly sensitive surface enhanced Raman scattering (SERS) detection of biomarkers. Nanostructuring is achieved by combining electron beam lithography so-called shadow evaporation technique which involves a two-step Au vapor deposition through suspended Ge mask while substrate tilted opposite directions. This results regular triangular pattern extremely small gap distances that...

The new definition of the kilogram, which is expected to be adopted by General Conference on Weights and Measures in 2018, will bring some major changes mass metrology. most fundamental change replacement present artefact-based with a universal definition, enabling principle any National Metrology Institute (NMI) realize kilogram. principles for realization dissemination kilogram revised SI are described mise en pratique This paper provides additional information explains how traceability...

The use of isotope dilution mass spectrometry (IDMS) to make measurements amount substance that are traceable the International System Units (SI) depends on an analysis possible sources uncertainty. A comprehensive application is presented law propagation uncertainty two-way IDMS method, which allows sensitivity coefficients be calculated and optimum regimes identified for carrying out measurements. This has allowed effect deviations from "exact matching" measurement evaluated first time....

Despite widespread use for more than two decades, the SERS phenomenon has defied accurate physical and chemical explanation. The relative contributions from electronic mechanisms are difficult to quantify often not reproduced under nominally similar experimental conditions. This work used electromagnetic modelling predict Raman enhancement expected three configurations: metal nanoparticles, structured surfaces, sharp tips interacting with surfaces. In each case, parameters such as artefact...

The possibility of achieving anti-Stokes stimulation and/or pumping under surface enhanced Raman scattering conditions has been the source intense controversies in literature. With aim clarifying some aspects this problem, we study theoretically and experimentally situation a model system which highlights difficulties interpretation data. We show that many assumptions often presumed literature need to be assessed with care each case. Through careful experiments show, particular,...