peptide conjugate did not reveal such reporting properties fluorescence of the free dye peptide conjugate 2 followed the initial trend similar to the nanoparticle conjugate the fluorescence intensity was largely suppressed above 55 u00b0 c fig1 and restored back to the original value after the cooling such reversible behavior of the free dye peptide was consistent with the general behavior of fluorophores under reversible thermal conditions in control experiments with the dye peptide conjugate fluorescence of the free dye peptide conjugate 2 was completely quenched above 55 u00b0 c fig8 in a clinical setting nanothermometers must respond quickly to heating preferably within seconds to avoid overheating of the treatment area gold nanorods carrying peptide u2014 dye conjugate 2 showed a response rate of 3 38 of fluorescence increase deg u2212 1 sec u2212 1 at the critical temperature and above fig1 this value provides a quantitative way of comparing future nanothermometers with improved design furthermore the results shown in fig9 demonstrate that the nanothermometers have an excellent response time within a few seconds their quick response was especially apparent when the switch between the heating and cooling processes occurred around 420 seconds in these experiments to construct a molecular thermometer the inventors conjugated a coumarin to rhodamine 640 which are optically active absorption and emission in the visible spectral range 380 650 nm 7 diethylaminocoumarin 3 carboxylic acid has the following structure these fluorophores are optically active absorption and emission in the visible spectral range 380 650 nm solvents dimethylsulfoxide dmso dichloromethane dcm dimethyl formamide dmf and methanol meoh fisher sigma aldrich were used without purification 7 diethylaminocoumarin 3 carboxylic acid was prepared as reported 14 rhodamine 640 was purchased from exciton n n diisopropylethylamine diea trifluoroacetic.