A smartphone fluorimeter capable of time-based fluorescence intensity measurements at various temperatures is reported. Excitation is provided by an integrated UV LED (λ = 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. All components are controlled using a smartphone battery powered Arduino microcontroller and a customised Android application that allows sequential fluorescence imaging and quantification every δt = 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 is observed to accelerate with an increasing rate constant, k = 1.94 min at T = 15 °C and k = 3.64 min at T = 30 °C, approaching a factor of ∼2 with only a change in temperature of ΔT = 15 °C. Thermally tuning these twist and bend associated rates to optimise sensor approaches and device applications is proposed.
The application of self-contained field-portable, internet connected spectroscopic diagnostics in food analysis using a fibre endoscopic smart fluorimeter is reported. A UV-induced fluorescence measure of the quality of olives oils, distinguishing between extra virgin and others, is identified and demonstrated with a smartphone platform. When excited at ~ 370 nm, the extra virgin olive oil fluoresces red at ~ 670 nm. Notably, other oils do not fluoresce red but rather blue, consistent with degradation of the chlorophyll in the oil. Artificial refinement employed in some of the commercial products removes the red emission providing a simple method for distinguishing extra virgin olive oil from all other oils. A smartphone endoscopic fluorimeter is designed and constructed that measures the emission band Δλ ~ (400 -700) nm with ~ 370 nm excitation. The instrument is used to characterise the fluorescence of the oils. Photo-degradation over time for extra virgin olive oil under room lights is observed, demonstrating the origin for the decomposition of extra virgin olive oil in transparent bottles. Extra virgin olive oils are also susceptible to thermally degrade more than refined oils.
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