Thermoplasmonic Effect of Surface-Enhanced Infrared Absorption in Vertical Nanoantenna Arrays

Thermoplasmonics is a method for increasing temperature remotely using focused visible or infrared laser beams interacting with plasmonic nanopartides. Here, local heating induced by mid-infrared quantum cascade laser illumination of vertical gold-coated nanoanterma arrays embedded into polymer layers is investigated by infrared nanospectroscopy and electromagnetic/thermal simulations. Nanoscale thermal hotspot images are obtained by a phototherrnal scanning probe microscopy technique with laser illumination wavelength tuned at the different plasmonic resonances of the arrays. Spectral analysis indicates that both Joule heating by the metal antennas and surface-enhanced-infrared absorption (SEIRA) by the polymer molecules located in the apical hotspots of the antennas are responsible for thermoplasmonic resonances, that is, for strong local temperature increase. At odds with more conventional planar nanoantennas, the vertical antenna structure enables thermal decoupling of the hotspot at the antenna apex from the heat sink constituted by the solid substrate. The temperature increase was evaluated by quantitative comparision of data obtained with the photothermal expansion technique to the results of electromagnetic/thermal simulations. In the case of strong SEIRA by the C=O bond of poly-methylmethacrylate at 1730 cm(-1), for focused mid-infrared laser power of about 20 mW, the evaluated order of magnitude of the nanoscale temperature increase is of 10 K. This result indicates that temperature increases of order of hundreds of K may he attainable with full mid-infrared laser power tuned at specific molecule vibrational fingerprints

Effects of isopropanol on collagen fibrils in new parchment

Background: Isopropanol is widely used by conservators to relax the creases and folds of parchment artefacts. At present, little is known of the possible side effects of the chemical on parchments main structural component- collagen. This study uses X-ray Diffraction to investigate the effects of a range of isopropanol concentrations on the dimensions of the nanostructure of the collagen component of new parchment. Results: It is found in this study that the packing features of the collagen molecules within the collagen fibril are altered by exposure to isopropanol. The results suggest that this chemical treatment can induce a loss of structural water from the collagen within parchment and thus a rearrangement of intermolecular bonding. This study also finds that the effects of isopropanol treatment are permanent to parchment artefacts and cannot be reversed with rehydration using deionised water. Conclusions: This study has shown that isopropanol induces permanent changes to the packing features of collagen within parchment artefacts and has provided scientific evidence that its use to remove creases and folds on parchment artefacts will cause structural change that may contribute to long-term deterioration of parchment artefacts. This work provides valuable information that informs conservation practitioners regarding the use of isopropanol on parchment artefacts

Rigid molecule approximation in memory function-based models for molecular liquids: Application to liquid water

In the present article we show how models for simple liquids can be used to describe the dynamics of atoms in molecular liquids within the rigid molecule approximation. We show in particular that the atomic masses are to be replaced by the corresponding Sachs-Teller masses and we derive a formal expression for the so-called Einstein frequency. The approach is illustrated for a model which has been originally developed for simple liquids and which has been used in the past to analyze quasielastic neutron scattering data from pure water and dilute aqueous solutions of apolar molecules. We obtain a remarkable agreement with results from molecular dynamics simulations not only in the quasielastic, diffusive regime, but also in the inelastic regime corresponding to intermolecular vibrations and fast molecular librations

Hydration of chloride anions in the NanC Porin from Escherichia coli: A comparative study by QM/MM and MD simulations

Chloride anions permeate the bacterial NanC porin in physiological processes. Here we present a DFT-based QM/MM study of this porin in the presence of these anions. Comparison is made with classical MD simulations on the same system. In both QM/MM and classical approaches, the anions are almost entirely solvated by water molecules. However, the average water–Cl− distance is significantly larger in the first approach. Polarization effects of protein groups close to Cl− anion are sizeable. These effects might modulate the anion-protein electrostatic interactions, which in turn play a central role for selectivity mechanisms of the channel

Role of effective atomic masses in memory function-based models for liquids: A simulation study of liquid water

In a simulation study of liquid water, the authors show that the single molecule dynamics up to 40 THz is well described by a rigid-body model for the second order memory function of the intermediate self-scattering function. ©2006 American Institute of Physic