Effect of Nanoparticle Size on Plasmonic Heat‐Driven Organic Transformation

Abstract

Plasmonic nanomaterials have the potential to convert light to heat energy in an efficient and localized fashion. Here, we report the use of plasmonic heat from gold nanoparticles (AuNPs) in performing an important chemical transformation of pyrone to pyridinone in water. The yield obtained using plasmonic heat (∼75%) is comparable to that obtained from normal heating at ∼90 °C. Further, this photothermally driven organic reaction is used as a tool to study the effect of NP size on the practical utilization of the plasmonic heat dissipated. AuNPs in the size regime of 10–24 nm are found to be most efficient in driving the pyrone to pyridinone conversion, which is attributed to the dependence of absorption cross‐section and heat capacity on the NP size. The results obtained are validated using conventional plasmonically driven solar‐vapor generation experiments. Our study proves the suitability of a thermally driven organic reaction for qualitatively comparing the effect of various NP parameters on the chemical effectiveness of the plasmonic heat, which can be crucial in our efforts to understand the role of thermalization process in different plasmonically powered processes.

Efficient Harvesting of >1000 nm Photons to Hydrogen via Plasmon-Driven Si–H Activation in Water

“…After photoexcitation, a nanoparticle’s plasmon decays in a few hundred femtoseconds to produce hot carriers. These carriers further lose their energies via electron–phonon and phonon–phonon coupling, leading to an increase in the nanoparticle’s surface temperature. ,− Both the hot carriers as well as the photothermal effect could enhance a chemical reaction ,,,,− as depicted in Figure c. To probe the possible involvement of the hot electrons in light-driven DMPS hydrolysis, the hydrogen production was studied with AuTNPs with trioctylamine (TOA) ligand present (Figure S12a).…”

Deciphering the Role of Light Excitation Attributes in Plasmonic Photocatalysis: The Case of Nicotinamide Cofactor Regeneration

“…Apart from the involvement of interband charge carriers, the photothermal effects and the plasmon-enhanced adsorbate excitation pathway can also contribute to the photoregeneration of NADH. The contribution from the photothermal effects will be predominant at the irradiation wavelengths close to the SPR bands of AuNRs (808 and 532 nm). , The superior photoregeneration of NADH at 450 nm excitation, along with the poor yield obtained in the thermal reaction under the dark (Figure S14), confirms that the contribution from the photothermal effects is negligible. The plasmon-enhanced adsorbate excitation pathway is known to dominate when the plasmon resonance or excitation wavelength spectrally overlaps with the electronic transition energy of the molecules adsorbed on the NP photocatalyst. , As shown in Figure S17, there is a negligible spectral overlap between the electronic transition energy of NAD + and the plasmon resonances/ excitation wavelengths used in the study.…”

“…The contribution from the photothermal effects will be predominant at the irradiation wavelengths close to the SPR bands of AuNRs (808 and 532 nm). 17,51 The superior photoregeneration of NADH at 450 nm excitation, along with the poor yield obtained in the thermal reaction under the dark (Figure S14), confirms that the contribution from the photothermal effects is negligible. The plasmonenhanced adsorbate excitation pathway is known to dominate when the plasmon resonance or excitation wavelength spectrally overlaps with the electronic transition energy of the molecules adsorbed on the NP photocatalyst.…”

“…Localized surface plasmon resonance (LSPR) in metal nanoparticles (NPs) offers a unique way of converting solar energy to chemical fuels, which forms the basis of the area of plasmonic photocatalysis. − Upon LSPR excitation, the plasmon can dephase via (i) a radiative pathway by creating intense electric field in the vicinity of the NP surface or (ii) nonradiative pathways by forming highly energetic hot charge carriers, which eventually dissipate their excess energy to the surroundings in the form of heat. − Literature reports establish that both radiative (near-field enhancement) and nonradiative (hot charge carriers and local heating) processes can activate molecules and trigger useful chemical transformations in the presence of light. − As a result, the mechanism involved in a plasmon-driven chemical transformation is complex. , A better understanding, as well as control over the involvement of different relaxation pathways, is essential to overcome the existing challenges of low product yield and selectivity in plasmonic photocatalysis. − Moreover, the contribution of different pathways will depend on the choice of the chemical reaction, photocatalyst design, and reactor design (light excitation, volume, temperature, colloidal/solid phase, fluid flow, etc. ). ,,− In this direction, we report here the conclusive role of light excitation and hot charge carriers in dictating the outcome of a plasmon-catalyzed chemical transformation.…”

Thermoplasmonics Enable the Coupling of Light into the Solvent-Mediated Self-Assembly of Gold Nanoparticles

“…Upon light irradiation, plasmonic AuNPs eventually dissipate the excess energy in the form of heat to the surroundings within a few picoseconds via a series of nonradiative relaxation steps (Landau damping, electron–electron, electron–phonon, and phonon–phonon interactions, Figure b). ,, The thermal energy dissipated is often termed as plasmonic heat and forms the basis for the area of thermoplasmonics. The fundamental and applied aspects of thermoplasmonics have been extensively documented in the literature. ,,− The importance of plasmonic heat lies in the huge amount of heat dissipated in a localized area. Our idea here was to use the plasmonic heat dissipated from Thy-AuNPs as the thermal energy source to evaporate the H 2 O from DMSO–H 2 O mixture.…”