“…2c ). The latter effect is called thermochromism, and it is explained as a decrement of the environmental polarity with the temperature rise 43 . These combined effects give our intensity-based method a sensitivity of around 0.5% per °C, which is comparable to other polymer-dye based methods 44 45 46 .…”
Nanoplasmonics has recently revolutionized our ability to control light on the nanoscale. Using metallic nanostructures with tailored shapes, it is possible to efficiently focus light into nanoscale field ‘hot spots'. High field enhancement factors have been achieved in such optical nanoantennas, enabling transformative science in the areas of single molecule interactions, highly enhanced nonlinearities and nanoscale waveguiding. Unfortunately, these large enhancements come at the price of high optical losses due to absorption in the metal, severely limiting real-world applications. Via the realization of a novel nanophotonic platform based on dielectric nanostructures to form efficient nanoantennas with ultra-low light-into-heat conversion, here we demonstrate an approach that overcomes these limitations. We show that dimer-like silicon-based single nanoantennas produce both high surface enhanced fluorescence and surface enhanced Raman scattering, while at the same time generating a negligible temperature increase in their hot spots and surrounding environments.
“…2c ). The latter effect is called thermochromism, and it is explained as a decrement of the environmental polarity with the temperature rise 43 . These combined effects give our intensity-based method a sensitivity of around 0.5% per °C, which is comparable to other polymer-dye based methods 44 45 46 .…”
Nanoplasmonics has recently revolutionized our ability to control light on the nanoscale. Using metallic nanostructures with tailored shapes, it is possible to efficiently focus light into nanoscale field ‘hot spots'. High field enhancement factors have been achieved in such optical nanoantennas, enabling transformative science in the areas of single molecule interactions, highly enhanced nonlinearities and nanoscale waveguiding. Unfortunately, these large enhancements come at the price of high optical losses due to absorption in the metal, severely limiting real-world applications. Via the realization of a novel nanophotonic platform based on dielectric nanostructures to form efficient nanoantennas with ultra-low light-into-heat conversion, here we demonstrate an approach that overcomes these limitations. We show that dimer-like silicon-based single nanoantennas produce both high surface enhanced fluorescence and surface enhanced Raman scattering, while at the same time generating a negligible temperature increase in their hot spots and surrounding environments.
“…In many cases thermochromic shifts in absorption and emission reflect the temperature induced changes in refractive index, n , and electric permittivity, ε , of the solvent as observed by our group in [1,2] for 4-aminophthalimide (4-AP) and Coumarin 153 (C153, Scheme 1) dissolved in several polar non-protic 1-chloroalkanes, or by Suppan et al in [3–6] for several probes including 4-AP.Scheme 1Coumarin 153 (C153) structure…”
In a recent paper (J Fluoresc (2011) 21:1547–1557) a temperature induced modulation of Coumarin 153 (C153) fluorescence lifetime and quantum yield for the probe dissolved in the polar, nonspecifically interacting 1-chloropropane was reported. This modulation was also observed in temperature dependencies of the radiative and nonradiative rates. Here, we show that the modulation is also observed in another 1-chloroalkane—1-chlorohexane, as well as in hydrogen bonding propionitrile, ethanol and trifluoroethanol. Change in the equilibrium distance between S0 an S1 potential energies surfaces was identified as the source of this modulation. This change is driven by temperature changes. It leads to a modulation of the fluorescence transition dipole moment and it is the primary source of the experimental effects observed. Additionally, we have found that proticity of the solvent induces a rise in the fluorescence transition dipole moment, which leads to a shortening of the fluorescence lifetime. Hydrogen bonds are formed by C153 also with hydrogen accepting solvents like propionitrile. We show that while such bonds do not affect the transition probability, they do change the S0 an S1 energy gap which in turn implies a change in non-radiative transition rate in a similar way as in protic solvents, as well as in the fluorescence spectrum position. Finally, the influence of temperature on the energies of hydrogen bonds formed by C153 when acting as hydrogen donor or acceptor is reported.
“…The nonspecific part of these interactions can be estimated analytically for simple systems, which has been the subject of the previous few papers. [3][4][5][6][7][8][9] Among the few probes used in these studies, 4-aminophthalimide (4-AP, Scheme 1) is the one most often used. Its properties have been recently widely described in ref.…”
Temperature induced spectral shifts of the 4-aminophthalimide (4-AP) emission spectra have been measured and compared to the predictions of the McRae solvent induced shift theory (J. Phys. Chem., 1957, 61, 562-572). Three moderately polar chloroalkanes selected as nonspecifically interacting media, and six hydrogen accepting or/and electron pair donating solvents have been used as the media in which the temperature influence on 4-AP-solvent interactions has been studied in the range of 180-320 K. Using the ab initio determined 4-AP ground state dipole moment and fitting appropriate expression originating from the mentioned theory to the shifts found in the chloroalkanes it has been possible to estimate the 4-AP excited state dipole moment, the probe excited state Onsager radius and its gas phase emission spectrum position. Using these values the thermochromic shifts of 4-AP emission spectra in hydrogen bond forming solvents have been predicted and compared to the experimental one. Temperature has been found to have different impact on the changes, upon excitation of the probe, in the mean values of the energies of different hydrogen bonds formed by 4-AP with solvents molecules.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
