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Deleterious chlorine fluorescence was found to occur at the same frequency as the Raman scattering of O2(1Δ) and O2(3Σ), seriously affecting the O2(1Δ) yield measurement in the reaction of chlorine with basic hydrogen peroxide by use of the Raman spectroscopy technique. To solve this problem we have taken advantage of the fact that Raman radiation is always strongly polarized while fluorescence is essentially non-polarized in a gaseous medium. When chlorine utilization of a singlet oxygen generator is 88%, O2(1Δ) yield reaches (42.4±7.4)% with the effect of chlorine fluorescence completely eliminated.

By using the concept of a high-pressure, gravity-independent singlet oxygen generator (SOG) proposed by Emanuel and based on the principle that a rotating fluid is capable of producing an enormous centrifugal force, a novel-type centrifugal-flow singlet oxygen generator (CFSOG) was designed and constructed. In this device, O2(1Δ) was generated in the reaction of gaseous Cl2 with a rotating basic hydrogen peroxide (BHP) liquid flow and then was removed from the BHP liquid phase by the centrifugal force. Meanwhile, the microdroplets formed during the Cl2+BHP reaction were removed from the O2(1Δ) gas flow by the centrifugal force produced by the high-speed flow along an arc-shaped channel. Preliminary investigations showed that, because the specific reactive surface area of this SOG was noticeably larger than that of the jet-SOG normally used in current chemical oxygen–iodine lasers (COILs), the O2(1Δ) yield of ~60%, the O2(1Δ) partial pressure as high as 31 Torr, and chlorine utilisation higher than 96% were realised. Moreover, steady operation was obtained.

The feasibility of singlet oxygen phosphorescence (SOP) lifetime imaging microscope was studied on a modified fluorescence lifetime imaging microscope (FLIM). SOP results from the infrared radiative transition of O2(a(1)Δg → X(3)Σg(-)) and O2(a(1)Δg) was produced in a C60 powder sample via photosensitization process. To capture the very weak SOP signal, a dichroic mirror was placed between the objective and tube lens of the FLIM and used to divide the luminescence returning from the sample into two beams: the reflected SOP beam and the transmitted photoluminescence of C60 (C60-PL) beam. The C60-PL beam entered the scanner of the FLIM and followed the normal optical path of the FLIM, while the SOP steered clear of the scanner and directly entered a finely designed SOP detection channel. Confocal C60-PL images and nonconfocal SOP images were then simultaneously obtained by using laser-scanning mode. Experimental results show that (1) under laser-scanning mode, the obstacle to confocal SOP imaging is the infrared-incompatible scanner, which can be solved by using an infrared-compatible scanner. Confocal SOP imaging is also expected to be realized under stage-scanning mode when the laser beam is parked and meanwhile a pinhole is added into the SOP detection channel. (2) A great challenge to SOP imaging is its extraordinarily long imaging time, and selecting only a few interesting points from fluorescence images to measure their SOP time-dependent traces may be a correct compromise.

We describe an improved technique for measuring the absolute O-2(a(1)Delta) concentration via the quantitative determination of IR radiation from O-2(a(1)Delta(g)-->X(3)Sigma(g)(-)) transition. An exact geometrical optical model was first established, in which the influence of reflection and refraction on the radiation characteristics of a luminous volume source was given full consideration, making possible the accurate calculation of the coupling efficiency between the volume source and a receiving area. Then, an IR radiation receiving apparatus (IRRRA) was constructed and its responsivity (mV/W) to the power of IR radiation calibrated by a tungsten standard lamp. An optical detection system was, in turn, built according to the optical model with fine alignment between the IRRRA and an optical cell. We then demonstrate the procedure to obtain the absolute concentration of O-2(a(1)Delta) flowing through the optical cell from a jet singlet oxygen generator from the signal of the IRRRA, the optical cell volume, and the coupling efficiency between the cell and the IRRRA. Moreover, to verify the accuracy of this method, the absolute O-2(a(1)Delta) concentration was compared to that measured by an established isothermal calorimetry method. Based on the comparison of the O-2(a(1)Delta) concentrations determined by the two methods, the Einstein A-coefficient was estimated as (2.70+/-0.84)x10(-4) s(-1), which agrees with Badger's value of 2.58x10(-4), Spalek's of 2.24x10(-4), Newman's of 2.19x10(-4), and Miller's of 2.3x10(-4) within the uncertainty of the experimental techniques. The method advanced in this article is worthwhile for the measurement of absolute O-2(a(1)Delta) concentration in a chemical oxygen iodine laser or a singlet oxygen generator. It can also provide a general technique for the measurement of absolute concentrations of long-lifetime luminous species other than O-2(a(1)Delta). (C) 2004 American Institute of Physics.

We have developed Lyso-V, the first fluorescent probe of lysosomal viscosity. Because of its lysosome-actived fluorescence characteristics, Lyso-V has proved to be an ideal lysosomal tracer with high spatial and temporal resolution under laser confocal microscopy. More importantly, Lyso-V shows its practical applicability in real-time quantification of lysosomal viscosity changes in live cells through fluorescence lifetime imaging microscopy.