Tunable Charge Transfer Plasmon at Gold/Copper Heterointerface

Abstract

Metal nanostructures with localized surface plasmon resonance (LSPR) have attracted great attention in catalysis, sensing, nanooptics, and nanomedicine. Charge transfer plasmon (CTP) is a LSPR mode that strongly depends on a conductive junction between metallic nanounits. Benefitting from the charge transfer junction, CTP provides a facile way to generate widely tunable LSPR with highly localized/enhanced light magnetic field and photothermal effect. The limited availability of highly tunable CTP structures and their fabrication techniques hinders a further pursuit of their functions and applications. In response to this situation, the present work aims at developing a simple while highly efficient synthetic route to width-adjustable Au/Cu heterojunctions capable of evoking tunable CTP behaviors. The strategy relies on a non-specific surface adsorption of low-cost, naturally occurred fish sperm DNA on a gold nanoseed to control heterogeneous copper nucleation. Such a process offers a chance to tailor the contact area between the gold and copper nano-domains in the bimetallic structure. Highly tunable CTP resonance from visible to near-infrared region is then realizable on the basis of this method. Experimental and calculated extinction spectra consistently reveal three key variables for the CTP structure, including the width of conductive junction and the sizes of gold and copper particles. These parameters are associated with DNA coverage, copper precursor concentration, and the synthetic conditions for gold nanoparticles, which allow for a CTP tuning from visible to near infrared wavelengths. By fully exploiting these highly controllable parameters, the maximally achievable CTP wavelength readily enters a near infrared II domain. The resulting CTP signals have a red-shift of up to 750 nm relative to the 530～570 nm LSPR peaks of individual gold and copper nanoparticles, corresponding to a very narrow Au/Cu conductive contact of 11～13 nm in width. The role of nonspecific DNA adsorption in the above process proves unique (currently irreplaceable) compared to other molecular adsorbates. The easily tunable Au/Cu heterointerface paves a way to integrated CTP and catalytic/sensing functions in future research.

Plasmonic Au–Cu nanostructures: Synthesis and applications

“…A twin defect and stacking fault were found to exist at the twinned Au nanotips, which led to Cu atoms being deposited on the twinned nanotip. In addition, Deng’s group developed width-adjustable Au–Cu Janus nanostructures by fish sperm DNA ( Figure 3E ) ( Zhu et al, 2020 ). The strategy relied on the non-specific surface adsorption of fish sperm DNA onto an Au nanoparticle to control heterogeneous Cu nucleation, which had low-cost and natural advantages.…”

“…(D) HAADF-STEM image and SEM image of Au–Cu Janus nanojellyfish ( Mi et al, 2022 ). (E) TEM images of Au–Cu heterodimers ( Zhu et al, 2020 ). (F) Schematic illustrating the synthesis of Au–Cu Janus nanostructures ( Fan et al, 2022 ).…”

Assembly and Healing: Capacitive and Conductive Plasmonic Interfacing via a Unified and Clean Wet Chemistry Route

“…The latter relies on solvent-induced double-layer neutralization and dehydration to realize DNA-directed NP coupling. To further enable a charge transfer between the coupled NPs, thermal/optothermal sintering or chemical welding can be adopted. − While these processes are highly effective, some challenges exist. First, AIS brings hard-to-remove Ag + contaminants to the NP surface, which adds great uncertainties to surface-dictated processes.…”

Sub-1.5 nm-gapped heterodimeric plasmonic nanomolecules

“…The strongly coupled nanoassembly behaves like a "nanomolecule" where a slight structural alteration dramatically modies its behaviors. [13][14][15][16][17][18] Localized surface plasmon resonance (LSPR) originating from light-induced collective electron oscillations in a metal nanostructure provides an ideal system to study subwavelength electromagnetic interactions. [19][20][21] We previously revealed that silver ion or less-polar solvents can induce strong plasmon coupling in DNA-tethered gold nanoparticle (AuNP) homodimers.…”