Single molecule Raman spectra of porphycene isotopologues

Abstract

Single molecule surface-enhanced resonance Raman scattering (SERRS) spectra have been obtained for the parent porphycene (Pc-d0) and its deuterated isotopologue (Pc-d12), located on gold and silver nanoparticles. Equal populations of "hot spots" by the two isotopologues are observed for 1 : 1 mixtures in a higher concentration range of the single molecule regime (5 × 10(-9) M). For decreasing concentrations, hot spots are preferentially populated by undeuterated molecules. This is interpreted as an indication of a lower surface diffusion coefficient of Pc-d12. The photostability of single Pc molecules placed on nanoparticles is strongly increased in comparison with polymer environments. Trans tautomeric species dominate the spectra, but the analysis of time traces reveals transient intermediates, possibly due to rare cis tautomeric forms.

Selective Excitation on Tip-Enhanced Raman Spectroscopy by Pulse Shaping Femtosecond Laser

“…The silver film is set as 150 × 150 × 60 nm 3 , with a complex permittivity, ε, taken from [40], and a permeability of μ = 1. The TERS spectra of large molecules, such as Rhodamine 6G, malachite, porphyrin, and DNA, were widely studied [2,7,10,12,13,[15][16][17][18][41][42][43]. The real part of the refractive index of these materials is mostly in the range of 1.5-1.7, and single molecular layer is of 0.5-0.6 nm thick.…”

“…To gain insight into intramolecular coupling, substrate coupling, and dynamic processes, Kyoung-Duck Park et al used TERS at variable and cryogenic temperatures, to slow and control the motion of a single molecule [16]. Besides, Raman spectroscopy of single molecule was used to study molecular isomerization and its intermediate processes [17].…”

Selective excitation of one among the three peaks of tip‐enhanced Raman spectroscopy by a shaped ultrafast laser pulse

“…Many Raman peaks in the range 1,000–1,700 cm −1 were measured simultaneously in the TERS spectra of Rhodamine 6G, malachite, porphyrin, and DNA . In this study, three Raman peaks were designated at 1,400, 1,520, and 1,600 cm −1 , respectively.…”

“…Many Raman peaks in the range 1,000-1,700 cm −1 were measured simultaneously in the TERS spectra of Rhodamine 6G, malachite, porphyrin, and DNA. [1,4,[45][46][47][48][49][50] In this study, three Raman peaks were designated at 1,400, 1,520, and 1,600 cm −1 , respectively. The center frequencies of the pump pulse ω p0 and Stokes pulse ω s0 are 14,000 and 12,500 cm −1 , and Δ p and Δ s are both 700 cm −1 .…”

“…The real and imaginary part of the refractive index was 1.6 and 0.1, respectively. These values were derived from TERS of large molecules, such as Rhodamine 6G, malachite, porphyrin, and DNA, [1,4,[45][46][47][48][49][50][59][60][61][62] where the real part of the refractive index of these materials was mostly in the range 1.5-1.7, and the thickness of the single molecular layer was 0.5-0.6 nm.…”