  A smartphone fluorimeter capable of time-based fluorescence intensity
measurements at various temperatures is reported. Excitation is provided by an
integrated UV LED (370 nm) and detection obtained using the in-built CMOS
camera. A Peltier is integrated to allow measurements of the intensity over T =
10 to 40 C with a maximum temperature resolution of DELTA T ~ 0.1 C. All
components are controlled using a smartphone battery powered Arduino
microcontroller and a customised Android application that allows sequential
fluorescence imaging and quantification every DELTA t = 4 seconds. The
temperature dependence of fluorescence intensity for four emitters (Rhodamine
B, Rhodamine 6G, 5,10,15,20-tetraphenylporphyrin and
6-(1,4,8,11-tetraazacyclotetradecane)2-ethyl-naphthalimide) are characterised.
The normalised fluorescence intensity over time of the latter chemosensor dye
complex in the presence of Zn ion is observed to accelerate with an increasing
rate constant, k = 1.94 min-1 at T = 15 C and k = 3.64 min-1 at T = 30 C,
approaching a factor of ~ 2 with only a change in temperature of DELTA T = 15
C. Thermally tuning these twist and bend associated rates to optimise sensor
approaches and device applications is proposed.
