We demonstrate measurement of the intrinsic fluorescence decay of a protein excited with a new and inexpensive optical source based on a light emitting diode (LED) giving 600 ps pulses at ∼280 nm. We believe this source will offer significant new capabilities for fluorescence research and development.

We demonstrate an AlGaN light-emitting diode ͑LED͒ giving pulses of ϳ600 ps full width half maximum, 0.35 W average power, 0.6 mW peak power, and ϳ12 nm bandwidth at 295 nm. This source is ideal for protein intrinsic tryptophan fluorescence decay research without the unwanted excitation of tyrosine and paves the way to lab-on-a-chip protein assays using fluorescence decay times. Fluorescence decay and anisotropy decay measurements of human serum albumin are reported and the usefulness of the 295 nm LED demonstrated in comparisons with a nanosecond flashlamp and LEDs with nominal wavelength emission of 280 nm.

In this paper, the authors explore the spectral properties of a sharp emission line centered at 499.6 nm (reported previously as 499 nm) observed in the UV‐luminescence spectrum of synthetic CVD diamond gemstones. These gemstones also exhibit spectrally prompt broad blue luminescence centered at 435 nm which is similar in character to the 425 nm blue luminescence characteristic of type IIa natural diamonds. By comparing the results against synthetic CVD diamond material which has been subjected to high temperature anneals, the authors can speculate on the nature of the defect associated with this color center. Since the 499 nm spectral line has only been observed in synthetic CVD diamonds to date, the authors further propose that it can be helpful in the identification of synthetic diamonds, in particular those showing the blue luminescence signature usually associated with type IIa natural diamonds.

Selective excitation of tryptophan fluorescence decay in proteins using a subnanosecond 295 nm light-emitting diode and time-correlated single-photon counting Appl. Phys. Lett. 86, 261911 (2005); 10.1063/1.1984088 Ultraviolet light-emitting diodes operating in the 340 nm wavelength range and application to time-resolved fluorescence spectroscopy Blue light-emitting diode demonstrated as an ultraviolet excitation source for nanosecond phase-modulation fluorescence lifetime measurements Rev.

Single molecule level detection of the near-infrared fluorescent protein allophycocyanin (APC) has been achieved using surface enhanced resonance Raman scattering (SERRS). The detection limit using the peak height of the 440 cm(-1) band was 1 x 10(-13) mol l(-1), compared to 2 x 10(-12) mol l(-1) for the fluorescence peak at 660 nm.