Light-to-heat conversion

Since noble metal NPs exhibit localized SPR, these plasmon resonant particles can not only have excellent light to heat conversion efficiencies, as discussed above, but also exhibit some non-thermal phenomena that could modulate the interaction between the carrier molecule and the bioactive molecule to be delivered. For example, Halas and his coworkers demonstrate... 

Light based on light-to-heat conversion [33]. In the first approach, carbon nanotubes (CNTs) were incorporated inside thermoresponsive poly(A-isopropylacrylamide) hydrogel. Light is absorbed by CNTs and converted into heat. The increase of temperature leads to deswelling of the hydrogel and unfolding of the 3D structure [33a]. In the second approach, pre-strained polystyrene (also known as Shrinky-Dinks) that... 

In addition to heat emission, radiative decay processes may also occur, in which light is emitted due to a transition from the lowest excited singlet or triplet state to the ground state (fluorescence or phosphorescence). In order to effect rapid and efficient conversion of optical energy (the laser) to heat, dyes which exhibit low fluorescence and in which excitation primarily involves the singlet states are the most suitable for heat-mode recording.196... 

The PAS phenomenon involves the selective absorption of modulated IR radiation by the sample. The selectively absorbed frequencies of IR radiation correspond to the fundamental vibrational frequencies of the sample of interest. Once absorbed, the IR radiation is converted to heat and subsequently escapes from the solid sample and heats a boundary layer of gas. Typically, this conversion from modulated IR radiation to heat involves a small temperature increase at the sample surface ( 10 6oC). Since the sample is placed into a closed cavity cell that is filled with a coupling gas (usually helium), the increase in temperature produces pressure changes in the surrounding gas (sound waves). Since the IR radiation is modulated, the pressure changes in the coupling gas occur at the frequency of the modulated light, and so does the acoustic wave. This acoustical wave is detected by a very sensitive microphone, and the subsequent electrical signal is Fourier processed and a spectrum produced. 

But not all materials emit the same amount of light when heated to the same temperature there is a spectral distribution of electromagnetic waves. For example, a piece of glass and a piece of iron when heated in the same furnace look different the glass is nearly colourless yet feels hotter to the skin because it emits more infrared light conversely, the iron glows because it emits visible as well as infrared light. 

This limiting value depends on the ambient temperature. The results suggest that the decomposition is mainly thermal due to the conversion of the light energy into heat. There is a small (5 to 10%) photochemical effect particularly when the nitrogen iodide is irradiated with blue or red light... 

Carbon particles in the size range we are considering can both absorb and scatter light. Light absorption and conversion to heat (consumptive absorption) are considered below. A further possibility is absorption and re-emission (fluorescence or phosphorescence) which are not explicitly considered here and seem unlikely. Scattering can also result in dispersion of the scattered light, and this is the possibility under consideration. 

---