Hybrid composite based on conducting polymers and plasmonic nanomaterials applied to catalysis and sensing

Abstract

Combining plasmonic and semiconductors offers significant potential in creating sensing and photocatalytic devices. Nanocomposites including both metals and semiconductors can control the charge states in the metals that can enhance catalysis activity along with plasmon-enhanced spectroscopy. Here we demonstrate the use of conducting polymer materials with plasmonic nanomaterials to boost 5-fold plasmon-enhanced Raman scattering spectroscopy signal strength and support oxidation of target molecules through supporting charge transfer processes. This work demonstrates the use of conducting polymers as a semiconductor platform to support plasmonic catalysis and sensing.

Dichalcogenide and Metal Oxide Semiconductor-Based Composite to Support Plasmonic Catalysis

“…The second mechanism is that plasmonic hot electrons leap off the surface of the metal, and the hot holes that are left behind on the metal oxidize PATP to DMAB. It has been found that if a sufficiently enough external stimulus was introduced into the system, PATP would be oxidized to PNTP rather than oxidized to DMAB. ,− PATP on AgNPs/ZnO (Figure b) produces a Raman spectrum that replicates for PATP on only AgNPs with the spectrum assigned to DMAB. In contrast, when PATP is present on AgNPs/MoS 2 , the substrate prevents the formation of DMAB.…”

“…For PNTP on AgNP/ZnO, the Raman spectra of PNTP is preserved, with the Raman spectra (Figure c) showing the same features as recorded for PNTP (Figure a). In contrast, when MoS 2 is added forming ZnO/MoS 2 /AgNP, PNTP partially converts to DMAB with the Raman spectra showing peaks assigned to PNTP and DMAB. − , …”

“…The Raman spectra of PATP and PNTP powder were first acquired using a dielectric substrate (Figure a). The Raman spectra shows A 1 modes with peaks at 1080 and 1595 cm –1 in agreement with literature values. ,,− The SERS spectrum of PATP on AgNPs (Figure b) reveals strong A 1 1077, 1190, and 1600 cm –1 in addition to b 2 modes at 1142 ascribed to C–H bend vibration, 1391 and 1440 cm –1 ascribed to the stretching vibration, and 1550 cm –1 for both frequency location and relative intensities. − It has been determined that a photocatalytic process takes place on the metal substrate, which is responsible for this difference in spectra when comparing PATP on a dielectric substrate to AgNPs. This photocatalytic process may result from the hot electrons formed when the Raman excitation laser excites the localized surface plasmon resonance (LSPR) of AgNPs. − ,− There are two possible mechanisms for this plasmon-driven oxidation of PATP to p , p ′-dimercaptoazobenzene (DMAB).…”

“…These generation “hot” electrons are seen as essential in catalysis through their interaction with the target chemical. However, hot electrons possess short subpicosecond lifetimes which presents a significant challenge for efficient surface plasmon-induced hot electron transfer catalytic reactions. − …”

“…Advanced materials and new techniques offer significant opportunities to advance control over surface catalytic reactions. − Such surface reactions can be potentially applied in a wide range of areas such as chemical production or for the removal of contaminants. Currently, used catalysts have well-known limitations regarding reactivity, selectivity, and/or stability. − For example, for many current industrial catalytic processes, catalysts require high temperatures and/or pressures to operate efficiently. , The use of plasmon resonances in metal nanostructures to control the rate and selectivity of photocatalytic reactions offers significant potential. − The localized surface plasmon resonance (LSPR) excitation of metal nanostructures produces enhanced light-matter interaction, resulting in a strongly enhanced plasmonic electromagnetic field on the surface of a plasmon active nanostructure. − The oscillation of free electrons quickly decays via the excitation of energetic electron–hole pairs. − These initially excited electrons rapidly thermalize and equilibrate via electron–electron scattering, creating a “hot” Fermi–Dirac distribution. − Then the hot distribution cools via the coupling between the “hot electrons” and the phonons of the metal lattice. These generation “hot” electrons are seen as essential in catalysis through their interaction with the target chemical.…”