239,765 research outputs found
SERS detection of food contaminants by means of portable Raman instruments
No full textSurface-enhanced Raman scattering (SERS) has been emerging as a powerful tool for the detection of a variety of analytes due to its very high sensitivity and fingerprinting recognition capabilities. Technological progresses in the equipment for Raman analysis are contributing to its transition from a technically demanding research method to a more widely available analytical technique. In particular, the commercialization of portable or handheld instruments has opened up the possibility of performing in situ analysis. In this review, a selection of the SERS substrates that are expected to be more suitable for use in combination with portable instruments is presented: Substrates are compared, for example, in terms of performance, reproducibility, ease of fabrication, and surface area. Moreover, this paper provides a survey of the current diffusion of portable Raman instruments in the SERS detection of food contaminants: The investigation of several analytes is summarized (mainly toxins, virus, bacteria, pesticides, forbidden food dyes, and preservatives), reporting on the limits of detection and on the eventual coupling with concentration or separation techniques. A brief perspective on possible future developments of the SERS detection with portable instruments is also provided
Validation of SERS enhancement factor measurements
No full textThe huge signal enhancement that motivates the rapid spreading of surface-enhanced Raman scattering (SERS) in a wide range of applications is commonly quantified by measuring the enhancement factor (EF). Concerning this important parameter, in this paper, we tackle 2 points: (a) We validate the use of a Macro Raman configuration with line focus to measure the EFs, against the more common Micro Raman one. The validation is carried out by comparing the EFs measured in the 2 configurations with the well-established methodology, on the same set of commercial substrates. Macro Raman with line focus can be advantageous over the Micro Raman because it can provide a higher signal-to-noise ratio at equal laser intensity impinging on the sample (useful in sensing or analytical applications). (b) It is a common practice for practitioners validating an experiment by measuring a commercial compound, acting as a “standard,” whose properties have been already determined in the literature: To our knowledge, an equivalent “standard” does not exist for EF measurements, probably due to the reproducibility and aging issues that prevent them from being identically reproduced in different laboratories. Because the EF is the cross-section ratio of a test molecule under SERS and normal Raman conditions, if one replaces the SERS substrate and the reference liquid with 2 commercial materials in the EF measurement procedure, this leads to the determination of another cross-section ratio: We propose then to use the cross-section ratio of suitable commercial materials for the validation of the instrumental procedure used to measure EFs
Silver nanoparticle aggregates: Wavelength dependence of their SERS properties in the first transparency window of biological tissues
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Holstein-Peirls-Hubbard trimer as a model for quadrupolar two-photon absorbing dyes
No full textThe linear and nonlinear optical properties of a Donor-Acceptor-Donor system have been investigated by using a two-electron three-point-site model system. Some basic features of electron correlations are included in the model by means of a bi-electronic density matrix. The polarizabilities and second hyperpolarizabilities have been computed with a modified version of the Collective Electronic Oscillators (CEO) method which allowed us to include the electron-phonon coupling. Both singly-and doubly-excited states are taken into account in the computation of (hyper-) polarizabilities. The effects of electron-phonon coupling on the two-photon absorption and on the third harmonic generation in the infrared region are discussed
The Importance of Pilot Studies
No full textThe term 'pilot studies' refers to mini versions of a full-scale study (also called 'feasibility' studies), as well as the specific pre-testing of a particular research instrument such as a questionnaire or interview schedule.
Pilot studies are a crucial element of a good study design. Conducting a pilot study does not guarantee success in the main study, but it does increase the likelihood.
Pilot studies fulfil a range of important functions and can provide valuable insights for other researchers. There is a need for more discussion amongst researchers of both the process and outcomes of pilot studies
Latent talent ontdekken en betrekken bij honoursonderwijs
No full textHoofdstuk 3 uit: Coppoolse, R., Van Eijl, P.J. & Pilot, A. (Red.) Hoogvliegers. Ontwikkeling naar professionele excellentie (pp 35-55). Rotterdam: University Press, Hogeschool van Rotterdam. (2013
Surface Enhanced Raman Spectroscopy: Principles, Substrates, and Applications
No full textSurface-enhanced Raman spectroscopy (SERS) is a spectroscopic technique that simultaneously combines fingerprint recognition capabilities, typical of vibrational spectroscopies, and very high sensitivity (down to single molecule), owing to the enhancement provided by plasmonic effects. Its discovery dates back to the 1970s, and since then, SERS has gained a lot of interest in the scientific community, as witnessed by the quick raise in the percentage of publications involving SERS, especially in the last two decades. In this book chapter, we would like to provide the reader with an overview of SERS, going from the illustration of its basic principles to the description of a wide selection of its applications. At first, the physical phenomena responsible for the electromagnetic and chemical SERS enhancements are described; thereafter, two key features of SERS, namely, its distance dependence and the concept of hot spot, are discussed, as well as the near- vs. far-field properties in plasmonic systems. Two sections are then dedicated to the materials that are more often used in SERS and to the strategies adopted to fabricate efficient SERS substrates. The last section illustrates the applications of SERS in several fields of sensing, like the detection of chemical warfare agents, environmental pollutants, food contaminants, and illicit drugs; the use of SERS in art preservation, forensic science, and medical diagnosis is also described, with specific and relevant examples from the most recent literature
Skylab Crew Health Trend SL4 PLT Jan 29, 1974
No full textA graph of Biomedical data labeled Crew Health Trend SL4 Pilot for the Pilot of Skylab 4, William R. Pogue
Pilot Projects in Water Management
No full textPilot projects appear in many forms in policy making and management. In an effort to understand the nature and use of pilot projects and improve their effectiveness, we undertake a practice-based and theoretical study of the pilot project phenomenon. First, we examine the roles assigned to pilot projects in the policy development literature and explore their use in a Dutch water innovation platform. Second, we determine characteristics of pilot projects to deepen insights into the nature of the pilot project phenomenon and the dimensions useful in the design of pilot projects. Third, we identify three pilot types and nine ways to use a pilot project and we develop a Pilot Project Nonagon that can be used to assess pilot projects’ uses and to compare stakeholders’ perspectives on these uses. Fourth, we identify hurdles to diffusion of the knowledge developed from pilot projects and suggest strategies to overcome these. Lastly, we formulate a research agenda aimed at addressing the identified knowledge gaps.Multi Actor SystemsTechnology, Policy and Managemen
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