Fluorescence advance

L. Graham, R. H. Nagaraj, R. Peters, L. M. Sayre, and V. M. Monnier, Structure and biological significance of pentodilysine, a novel fluorescent advanced Maillard reaction protein crosslink, in F, 1998, 410. 

Yi, G.S. and Chow, G.M. (2006) Synthesis of hexagonal-phase NaYF4 Yb,Er and NaYR4 Yb,Tm nanocrystals with efficient up-conversion fluorescence. Advanced Functional Materials, 16, 2324—2329. 

H. Obayashi, K. Nakano, H. Shigeta, M. Yamaguchi, K. Yoshimori, M. Fukui, M. Fujii, Y. Kitagawa, N. Nakamura et al.. Formation of crossline as a fluorescent advanced glycation end product in vitro and in vivo, Biochem. Biophys. Res. Commun., 226 (1996) 37-41. 

Raman spectroscopy has become a most important tool for characterization of polymers as low frequency lasers have improved so Raman spectroscopy excited in the infrared frequency range can be used to minimize the effect of fluorescence. Advances in Raman instrumentation have been dramatic and the polymer spectroscopists must now seriously consider the use of Raman as complementary to infrared. In many cases Raman spectroscopy will be the preferred method as the many new applications in this revised chapter illustrate. 

Experimental access to the probabilities P(E ,E) for energy transfer in large molecules usually involves teclmiques providing just the first moment of this distribution, i.e. the average energy (AE) transferred in a collision. Such methods include UV absorption, infrared fluorescence and related spectroscopic teclmiques [11. 28. 71. 72, 73 and 74]. More advanced teclmiques, such as kinetically controlled selective ionization (KCSI [74]) have also provided infonnation on higher moments of P(E ,E), such as ((AE) ). 

Lee D and Albrecht A C 1985 A unified view of Raman, resonance Raman, and fluorescence spectroscopy (and their analogues in two-photon absorption) Advances in Infrared and Raman Spectroscopy vo 12, ed R J H Clark and R E Hester (New York Wiley) pp 179-213... 

It is interesting to note the analogy of developments in light microscopy during the last few decades. The confocal microscope as a scaiming beam microscope exceeds by far the nomial fluorescence light microscope in resolution and detection level. Very recent advances in evanescent wave and interference microscopy seem to promise to provide even higher resolution (B1.18). 

Figure Cl.5.2. Fluorescence excitation spectra (cps = counts per second) of pentacene in /i-teriDhenyl at 1.5 K. (A) Broad scan of the inhomogeneously broadened electronic origin. The spikes are repeatable features each due to a different single molecule. The laser detuning is relative to the line centre at 592.321 nm. (B) Expansion of a 2 GHz region of this scan showing several single molecules. (C) Low-power scan of a single molecule at 592.407 nm showing the lifetime-limited width of 7.8 MHz and a Lorentzian fit. Reprinted with pennission from Moemer [198]. Copyright 1994 American Association for the Advancement of Science.

The more advanced spectrofluorimeters are capable of automatically scanning fluorescent spectra between about 200 and 900 nm and produce a chart record of the spectrum obtained. These can also operate at a fixed wavelength and are equally suitable for carrying out quantitative work their main application tends to be for the detection and determination of small concentrations of organic substances. 

Advances in laser technology now allow for solid-state lasers of high beam quality. These beams may be projected from a much smaller auxiliary telescope, which negates the need for optical switching and completely eliminates any main telescope fluorescence. Solid-state YAG lasers are the most common type of lasers commercially available. These lasers use a crystal as the lasing... 

Direct Measurement of HO, in the Troposphere. Techniques to measure tropospheric concentrations of HO have been reviewed (O Brien Hard, submitted to Advances in Chemistry, 1991) so only a summary will be given here. The most extensively researched technique for [HO ] measurement in the troposphere is based on laser-induced fluorescence (LIF) of HO. This approach has been developed in many configurations directing the laser into the free atmosphere and collecting fluorescence back scatter (LIDAR) (105,106,107) LIF of air sampled at atmospheric pressure... 

The sensitivity of the fluorescence methods varies considerably with the instrument used. Advances in modern instrumentation and the power of today s computers allow for a much improved sensitivity. Using commercially available instruments and modern computers equipped with appropriate software, detection limits down to 10 pg of calf thymus DNA can be achieved using ethidium bromide. (We have achieved such levels using several Perkin-Elmer MPF66 Instruments at various locations.)... 

Several books and symposium proceedings on luminescence standards and measurements have been published in the last several years, including "Advances in Standards and Methodology in Spectrophotometry" (i), "Measurement of Fhotolumlnescence" (2), "Standards in Fluorescence Spectrometry" (J), and "Modern Fluorescence Spectroscopy" (Volumes 1-4) (4). These books, the references within them, and the classic in the field, "Photoluminescence of Solutions" by C.A. Parker (5), provide the researcher with extensive information about luminescence standards and measurements. 

Luminescence science has developed into a powerful tool for studying nature in macro- and microenvironments. At present, there are many scientiflc advances being reported that incorporate fluorescence technology into the research regimen. I expect this trend to continue as the scientiflc community becomes more cognizant of the knowledge to be gained by use of luminescence techniques. 

Direct observation of molecular diffusion is the most powerful approach to evaluate the bilayer fluidity and molecular diffusivity. Recent advances in optics and CCD devices enable us to detect and track the diffusive motion of a single molecule with an optical microscope. Usually, a fluorescent dye, gold nanoparticle, or fluorescent microsphere is used to label the target molecule in order to visualize it in the microscope [31-33]. By tracking the diffusive motion of the labeled-molecule in an artificial lipid bilayer, random Brownian motion was clearly observed (Figure 13.3) [31]. As already mentioned, the artificial lipid bilayer can be treated as a two-dimensional fluid. Thus, an analysis for a two-dimensional random walk can be applied. Each trajectory observed on the microscope is then numerically analyzed by a simple relationship between the displacement, r, and time interval, T,... 

XRF nowadays provides accurate concentration data at major and low trace levels for nearly all the elements in a wide variety of materials. Hardware and software advances enable on-line application of the fundamental approach in either classical or influence coefficient algorithms for the correction of absorption and enhancement effects. Vendors software packages, such as QuantAS (ARL), SSQ (Siemens), X40, IQ+ and SuperQ (Philips), are precalibrated analytical programs, allowing semiquantitative to quantitative analysis for elements in any type of (unknown) material measured on a specific X-ray spectrometer without standards or specific calibrations. The basis is the fundamental parameter method for calculation of correction coefficients for matrix elements (inter-element influences) from fundamental physical values such as absorption and secondary fluorescence. UniQuant (ODS) calibrates instrumental sensitivity factors (k values) for 79 elements with a set of standards of the pure element. In this approach to inter-element effects, it is not necessary to determine a calibration curve for each element in a matrix. Calibration of k values with pure standards may still lead to systematic errors for unknown polymer samples. UniQuant provides semiquantitative XRF analysis [242]. 

Raman spectroscopy has enjoyed a dramatic improvement during the last few years the interference by fluorescence of impurities is virtually eliminated. Up-to-date near-infrared Raman spectrometers now meet most demands for a modern analytical instrument concerning applicability, analytical information and convenience. In spite of its potential abilities, Raman spectroscopy has until recently not been extensively used for real-life polymer/additive-related problem solving, but does hold promise. Resonance Raman spectroscopy exhibits very high selectivity. Further improvements in spectropho-tometric measurement detection limits are also closely related to advances in laser technology. Apart from Raman spectroscopy, areas in which the laser is proving indispensable include molecular and fluorescence spectroscopy. The major use of lasers in analytical atomic... 

The advancement of the application of lasers in combination with the molecular beam technique has made a great impact in the understanding of primary photodissociation processes. For state-specific detection of small fragments, laser-induced fluorescence, multiphoton ionization, and coherent laser scattering have provided extremely detailed information on the dynamics of photodissociation. Unfortunately, a large number of interesting... 

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