Richard M. Miller

Time-resolved fluorescence with an optical-fiber probe

Abstract Time-resolved fluorescence measurements are made with an optical-fiber probe approximately 16 m long. Fluorescence lifetimes for 1.00 μM solutions of rhodamine-B and rose bengal in ethanol were found to be 2.78 ± 0.04 ns and 0.77 ± 0.07 ns, respectively, similarin accuracy and precision to values obtained with conventional techniques. Calculations are used to investigate the limitations in remote determinations caused by temporal broadening. Results indicate that fiber lengths approaching 1 km can be used without significant loss in accuracy or precision.

Tutorial review—Applications of confocal laser scanning microscopy in in-situ mapping

A confocal laser scanning microscope has been applied to the detailed study of non-invasive mapping on targeted systems. This paper aims to show, by particular reference to specific problems, the wide ranging potential of the technique for the analytical community. The specific problems successfully tackled by the technique include characterization of two types of inert support bodies and the precursor/enzyme distributions therein, the effect of processing on dye penetration in fibres, mapping the interdependence and growth patterns in bacterial colonies and non-invasive examination of epidermal tissue layers.

Impulse response photoacoustic spectroscopy of biological samples

The use of a pseudo-randomly modulated optical beam and a cross-correlation signal recovery technique to obtain impulse response photoacoustic signals is demonstrated. The application of this technique to provide depth-related physical and chemical information from plant tissues is described.

On the Feasibility of Passive Optical Separation of Scatter and Fluorescence

The use of “flat” focusing devices, such as Fresnel lenses and holographic optical elements, for the passive optical separation of fluorescence and scattered light is evaluated theoretically and experimentally. Although “flat” lenses do not focus incident light isochronically, and should therefore have different spatial focusing characteristics for very short pulses (scattered light) and pseudo-continuous-wave signals (fluorescence), the optical quality of the flat lenses tested is insufficient to achieve such discrimination. Additionally, if the coherence length of the fluorescence is less than the difference in optical pathlength from extreme positions on the flat lens, fluorescence cannot be considered to be a pseudo-cw signal; this limitation constrains the potential applications of such instrumentation.

Industrial applications of spectroscopic imaging

Many consumer products are complex physico-chemical systems, and there is a need to characterize them in the three spatial dimensions and in time. Spectroscopic imaging provides the opportunity to do this non-destructively and in-situ. New developments in detector technology, microscope optics and spectroscopics probes are beginning to generate new types of imaging experiments. Several application examples are given covering both macro- and micro-imaging.

Study of dynamic processes by impulse response photoacoustic spectroscopy

Impulse response photoacoustic spectroscopy has been used to study variations in chromophore distribution with time in a dynamic system. A system in which a dye diffuses through a polymer film has been examined, and it is shown that it is possible to monitor the diffusion process in situ and non-destructively. Comparison of the experimental results with a theoretical model demonstrates that the results are consistent with classical diffusion processes.

Design of a computer-controlled electroanalytical system

A dedicated high-level computer language has been written for use with a computer-controlled electroanalytical system. The language can be compiled to produce executable machine code modules, and provides considerable flexibility in the design of experiments. The compiled modules can be linked to programs in other high-level languages, allowing very complex strategies to be implemented. The language is sufficiently general to allow extension to the control of other types of analytical instrumentation.

Thermal wave imaging of multi-layered films

Monitoring of the physical structure of a multi-layered composite film presents difficult analytical problems. Thermal wave imaging is used to distinguish between different layers of a photographic film and to provide information on the internal three-dimensional distribution of chromophores.