Sensor devices for quantifying luminescent targets are described herein. An example device comprises a light source for exciting the targets, thus generating luminescence signals and a detector for detecting these signals, resulting in a detected signal which comprises a desired signal originating from the targets and a background signal. It moreover comprises a bleaching device for bleaching of at least part of the sources generating the background signal and a processor configured to trigger the bleaching device to start bleaching, and to trigger the light source for exciting the remaining luminescent targets which are not bleached, and to trigger the detector for detecting the luminescence signal of the remaining luminescent targets, so as to generate a measurement signal representative for the quantification of the luminescent targets.

A method is provided for verifying the authenticity of an article which bears a security mark. The method includes irradiating the security mark with a time-varying light source, ascertaining at least one portion of the emissions spectrum of the irradiated security mark with at least one photodetector, determining the photoluminescence lifetime of the security mark by monitoring the time or frequency response of the photodetector, and verifying the authenticity of the article only if the security mark exhibits a photoluminescence which has a lifetime that falls within the range of appropriate values for each portion of the photoluminescence spectrum for which the photoluminescence lifetime of said security mark was ascertained.

A fluorescence and phosphorescence detection device includes a fluorescence and phosphorescence sensor, a data acquiring unit, and an emission detection unit. The fluorescence and phosphorescence sensor includes a light source that emits an excitation light of a predetermined wavelength, and a photodetection unit that detects fluorescence emission and phosphorescence emission excited from the paper sheet by the excitation light. The data acquiring unit acquires a time-series waveform of a signal outputted from the fluorescence and phosphorescence sensor in response to the detection of the emission in the photodetection unit. The emission detection unit detects the fluorescence emission from the time-series waveform of a period in which the excitation light is emitted from the light source and detects the phosphorescence emission from an attenuation curve appearing on the time-series waveform of a period in which emission of the excitation light from the light source is stopped.

The present invention relates to a method for detecting time-resolved fluorescence based on a principle of phase balanced frequency multiplication modulation. A stimulating light source modulated by using a baseband signal acts on a to-be-measured target to trigger fluorescence, so that the fluorescence intensifies and decays periodically; then, a frequency-doubled square signal is used to control a sampling period and divide an ascending period of the fluorescence into two and a decay period of the fluorescence into two; after independent sampling is performed separately, sampling differences of the two parts are separately calculated and then added to obtain an intensity representative value of a fluorescence signal and to obtain a concentration value of the to-be-measured target. The method in the present invention can not only likewise cancel fluorescence interference of a substrate in a sample, but also can cancel ambient bias light, power-frequency interference of a spatial electromagnetic wave or other signals, and therefore improves signal intensity in fluorescence measurement on the detection sample, has an advantage that cannot be accomplished in a conventional time-resolved fluorescence method, and can be applied in fluorescence intensity detection of a target in fields such as biology, chemistry, and medicine.

Some embodiments described herein relate to a sensor that includes a first a first polymer-luminescent sensing compound configured to produce a first luminescent signal in the presence of a first analyte and a second polymer-luminescent sensing compound configured to produce a second luminescent signal in the presence of a second analyte. The second luminescent signal can have a luminescent lifetime that is at least 1.1 times greater than a luminescent lifetime of the first luminescent signal. Such temporally differences in signal can be used to deconvolute the first luminescent signal from the second luminescent signal even when, for example, the first luminescent signal and the second luminescent signal have the same or a similar emission spectrum.

A method is provided for verifying the authenticity of an article which bears a security mark. The method includes irradiating the security mark with a time-varying light source, ascertaining at least one portion of the emissions spectrum of the irradiated security mark with at least one photodetector, determining the photoluminescence lifetime of the security mark by monitoring the time or frequency response of the photodetector, and verifying the authenticity of the article only if the security mark exhibits a photoluminescence which has a lifetime that falls within the range of appropriate values for each portion of the photoluminescence spectrum for which the photoluminescence lifetime of said security mark was ascertained.

A method of characterising a composition of a gemstone comprises irradiating an upper portion and a lower portion of the gemstone with one or more pulses of ultraviolet radiation at a wavelength of substantially 225 nm or less; capturing luminescence emitted by the upper portion of the gemstone and luminescence emitted by the lower portion of the gemstone in one or more time windows having a predetermined relationship with the or each pulse; and comparing properties of the captured luminescence from the upper and lower portions. A composition of the gemstone is characterised, based upon the comparison.