Silicon Photodiodes For Detection Research Articles

A Portable, Low-Cost, LED Fluorimeter for Middle School, High School, and Undergraduate Chemistry Labs

A low-cost portable fluorimeter was constructed using a 360 nm LED for excitation and a silicon photodiode for detection. The instrument is simple to operate and has been used to investigate fluorescent whitening agents extracted from various brands of paper, to determine the linear range and limit of detection of quinine in various commercial tonic water samples, and to quantify the amount of vitamin B1 in commercial multivitamin supplements. The instrument is straightforward to construct and to use and facilitates the introduction and hands-on application of spectroscopy, fluorescence, and related topics in middle school, high school, and undergraduate laboratory courses.

The Characterization of an Easy-to-Operate Inexpensive Student-Built Fluorimeter

A compact, rugged, and portable fluorimeter was designed and constructed using a 460 nm light-emitting diode for the excitation and a silicon photodiode for detection. The total cost of such an instrument is less than $110, thus allowing for deployment of multiple instruments at low cost. The fluorimeter is easy to operate and has been successfully used to quantify fluorescein in commercial-brand antifreeze and chlorophyll a pigment in spinach leaves. The mini instrument and the associated experiments have provided for a novel approach to teaching the principles and applications of spectroscopy and fluorescence to a wide academic variety of students.

A low-cost, portable, and quantitative spectral imaging system for application to biological tissues

The ability of diffuse reflectance spectroscopy to extract quantitative biological composition of tissues has been used to discern tissue types in both pre-clinical and clinical cancer studies. Typically, diffuse reflectance spectroscopy systems are designed for single-point measurements. Clinically, an imaging system would provide valuable spatial information on tissue composition. While it is feasible to build a multiplexed fiber-optic probe based spectral imaging system, these systems suffer from drawbacks with respect to cost and size. To address these we developed a compact and low cost system using a broadband light source with an 8-slot filter wheel for illumination and silicon photodiodes for detection. The spectral imaging system was tested on a set of tissue mimicking liquid phantoms which yielded an optical property extraction accuracy of 6.40 +/- 7.78% for the absorption coefficient (micro(a)) and 11.37 +/- 19.62% for the wavelength-averaged reduced scattering coefficient (micro(s)').

Use of a silicon photodiode for detection of weak transient absorption in flash photolysis experiments

An inexpensive silicon photovoltaic detector has been used in this laboratory for detecting weak transient absorptions for lifetimes to greater than 10 mu s in the wavelength range 0.6-1.15 mu m after flash photolysis of liquids and plastics. No cooling is necessary and transient optical densities of 0.001 can be measured with an uncertainty of +or-20%.