The Hedley Lab is based in bespoke new optics labspace in the Joseph Black Building at the University of Glasgow. We also have access to sample preparation facilities, gloveboxes, and spin coaters for material handling and making single molecule samples.
Most of our work involves measuring the optical spectroscopy of light emitting materials in solution, film and in single molecule samples, thus most of our work is concentrated in our optics lab.
At the heart of our single molecule work is our confocal fluorescence microscope. We have a Nikon Ti2-u microscope base that is accessorised with a Physik Instrument piezo for sample scanning on top of a large travel manual stage for coarse positioning. We have visible and UV high NA objectives available for excitation/PL collection. Laser excitation is provided by the sources detailed below, but essentially we have the option of excitation at any visible/UV wavelength.
Our microscope, piezo and photoluminescence detection are all controlled by homecoded python software that allow us to develop custom measurement routines to enable the novel work we are pursuing.
Photoluminescence from the microscope is detected confocally before being distributed amongst four SPAD point detectors to allow reconfigurable detection of different spectral/polarisation information. Each detector has a time resolution of ~ 50 ps (FWHM). We have a further two hybrid-PMT single photon detectors for measuring photoluminescence in the UV/blue regions.
Photon counts on each of the channels are then recorded by our PicoQuant HydraHarp picosecond event timer. This gives us time-tagged arrival times of each photon on the macroscopic (time since start of experiment) and microscopic (time since last laser pulse) timescales. We save all of this data for later post-processing with 40 TB of online and offline storage.
We have an array of excitation sources for use in our single molecule measurements. On the picosecond timescale we have an 8-channel PicoQuant Sepia II laser driver, allowing pulses from single shot up to 80 MHz, in any programmable pattern from regular pulsing through to packet bursts for measurement of materials with long (μs-ms) lifetimes. This drives laser diodes, currently a 375 or 405 nm, giving ~70 ps pulses (FWHM).
We will also soon purchase a tunable femtosecond source for use with the confocal fluorescence microscope. This will be coupled through a pulse-picker to give control of the repetition rate.
We also have a sample chamber for conventional solution and film TCSPC. Collected PL is coupled through a monochromator before being directed into our SMS detection box for recording of lifetimes with the SPADs & TCSPC.
With fs excitation lifetimes down to ~100 ps are resolvable with SPAD detection. At the other end of the time window, when used with the Sepia and picosecond laser diodes in burst mode we can measure long lifetimes out to milliseconds.
We installed multicolour under-table LEDs, because everything has multicolour LEDs in the twenty first century. It can also be used to communicate whether a measurement is in progress or not!