Doing chemistry with plasmons is rewarding but is often challenged by the competition between the intriguing relaxation processes in plasmonic materials. One of the currently debated and prominent examples of this is the interference of the thermalization process in bringing out different physicochemical transformations. We present here insights into the utilization and quantification of thermoplasmonic properties in configurable arrays of gold nanorods (AuNRs), which will help in accomplishing the desired outcome from the thermalization process. The plasmonic heat generated in AuNR arrays is used to perform versatile and useful photothermal processes, such as polymerization, solar-vapor generation, Diels−Alder reaction, and crystal-to-crystal transformation. The unprecedented use of thermochromism in quantifying the thermalization process shows that the surface of AuNR arrays can heat up to ∼250 °C within ∼15 min of irradiation, which is independently validated with standard infrared-based thermometric imaging studies. The plasmonic heat reported by the thermochromic studies is the lower limit corresponding to the phase change temperature of the thermochromic molecule, and the actual surface temperature of bundled AuNR arrays could be higher. The choice of reaction conditions is crucial for the effective utilization as well as dissipation of thermoplasmonic heat. The maximum impact of surface temperature was observed when substrates were adsorbed onto the AuNR arrays, whereas the influence of thermoplasmonic heat was minimum when the experiments were performed in a solution state. The insights provided here will have far-reaching implications in the emerging area of plasmonically powered processes, especially in plasmonic photocatalysis.

Soft graphitizable carbon-based multifunctional nanomaterials have found versatile applications ranging from energy storage to quantum computing. In contrast, their hard-carbon analogues have been poorly investigated from both fundamental and application-oriented perspectives. The predominant challenges have been (a) the lack of approaches to fabricate porous hard-carbons and (b) their thermally nongraphitizable nature, leading to inaccessibility for several potential applications. In this direction, we present design principles for fabrication of porous hard-carbon-based nanostructured carbon florets (NCFs) with a highly accessible surface area (∼936 m2/g), rivalling their soft-carbon counterparts. Subjecting such thermally stable hard-carbons to a synergistic combination of an electric field and Joule heating drives their transformation to free-standing macroscopic monoliths composed of onion-like carbons (OLCMs). This represents the first such structural transformation observed in sp2-based hard-carbon NCFs to sp2-networked OLCMs. Micro-Raman spectroscopy establishes the simultaneous increase in the intensity of D-, 2D-, and D + G-bands at 1341, 2712, and 2936 cm–1 and is correlated to the reorganization in the disordered graphitic domains of NCFs to curved concentric nested spheres in OLCMs. This therefore completely precludes the formation of a nanodiamond core that has been consistently observed in all previously reported OLCs. The Joule heating-driven formation of OLCMs is accompanied by ∼5700% enhancement in electrical conductivity that is brought about by the fusion of outermost graphitic shells of OLCs to result in monolithic OLC structures (OLCMs). The porous and inter-networked OLCMs exhibit an excellent adsorption-based capture of volatile organic compounds such as toluene at high efficiencies (∼99%) over a concentration range (0.22–1.86 ppm) that is relevant for direct applications such as smoke filters in cigarettes.

The electric field at the sharp pointed tips of single wall carbon nanotube ensembles has been utilized to kinetically accelerate hitherto unobserved chemical reactions at the heterogeneous solid–gas interfaces. The principle of ″action-of-points″ drives specific chemical reactions between the defect sites of single wall carbon nanotubes (CNTs) and ppb levels of gaseous hydrogen sulfide. This is manifested as changes in the electrical conductivity of the conductive CNT-ensemble (cCNT) and visually tracked as enthalpic modulations at the site of the reaction through infrared thermometry. Importantly, the principle has been observed for a variety of analytes such as NH3, H2O, and H2S, leading to distinctly correlatable changes in reactivity and conductivity changes. Theoretical calculations based on the density functional theory in the presence and absence of applied electric field reveal that the applied electric field activates the H2S gas molecules by charge polarization, yielding favorable energetics. These results imply the possibility of carrying out site-specific chemical modifications for nanomaterials and also provide transformative opportunities for the development of miniaturized e-nose-based gas analyzers.

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