Indirect Nanoplasmonic Sensing: Ultrasensitive Experimental Platform for Nanomaterials Science and Optical Nanocalorimetry

Abstract

Indirect nanoplasmonic sensing is a novel experimental platform for measurements of thermodynamics and kinetics in/on nanomaterials and thin films. It features simple experimental setup, high sensitivity, small sample amounts, high temporal resolution (<10(-3) s), operating conditions from UHV to high pressure, wide temperature range, and applicability to any nano- or thin film material. The method utilizes two-dimensional arrangements of nanoplasmonic Au sensor-nanoparticles coated with a thin dielectric spacer layer onto which the sample material is deposited. The measured signal is spectral shifts of the Au-sensor localized plasmons, induced by processes in/on the sample material. Here, the method is applied to three systems exhibiting nanosize effects, (i) the glass transition of confined polymers, (ii) catalytic light-off on Pd nanocatalysts, and (iii) thermodynamics and kinetics of hydrogen uptake/release in Pd nanoparticles <5 nm. In (i) and (iii), dielectric changes in the sample are detected, while (ii) demonstrates a novel optical nanocalorimetry method.

Refractive Index Sensing with Subradiant Modes: A Framework To Reduce Losses in Plasmonic Nanostructures

“…A perturbation of the dielectric permittivity Δε over a volume V is now assumed. Using perturbation theory, the shift Δω of the frequency of the mode is given by 10,12 Δω = À Δn n ω 0 AEE 0 jE 0 ae V (8) where the scalar product of the field is restricted to the volume V of perturbation. Equation 8 is equivalent to eq 2.…”

“…It has been recently combined with nanooptical trapping and manipulation 6,7 and extended to other sensing concepts such as nanocalorimetry. 8 Compact plasmonic resonators also enable reaching a subcellular resolution, which has the potential to improve the understanding of subcellular processes. 5,9 From the optical point of view, a shift of the resonance frequency of a plasmonic resonator occurs when the dielectric properties of the local environment change upon binding of any analyte under study.…”

Nanoplasmonic sensing for nanomaterials science

“…The principle behind calorimetry is that by measuring the energy dissipation from an exothermic process one obtains a direct measure for, e.g., the conversion effi ciency of a catalyst or the latent heat of a phase transition. Optical calorimetry -type measurements were fi rst demonstrated by Langhammer et al who showed, using their " INPS " platform depicted in Figure 3 A, that it is possible to use the temperature readout to scrutinize size-dependent catalytic activity of Pd nanoparticles in situ [34] . Their fi nding also demonstrated that any indirect nanoplasmonic sensor can provide two different readouts, a dielectric one and a temperature one.…”

“…Langhammer et al successfully used the INPS-platform to study size-effects in hydride formation and decomposition thermodynamics [34,62] and kinetics [34,63] of small Pd nanoparticles (D < 8 nm). Also here " calibration " of the INPS platform was made, i.e., a linear scaling of the response of the INPS sensor with the absolute hydrogen concentration in the studi ed Pd nanoparticles was found by complementary QCM experiments [34] .…”

“…Langhammer et al studied the size-/ thickness dependence of the glass transition temperature, T g , in polystyrene (PS) nanoparticles and thin fi lms of atactic poly(methyl methacrylate) (PMMA) using the INPS platform shown in Figure 3A [34] . The glass transition in polymers is related to signifi cant slowing of the motion of polymer chain segments when cooled below T g .…”