Optical monitoring of faradaic reaction using single plasmon-resonant nanorods functionalized with graphene

Wireless electrical-molecular quantum signalling for cancer cell apoptosis

Quantum biological tunnelling for electron transfer is involved in controlling essential functions for life such as cellular respiration and homoeostasis. Understanding and controlling the quantum effects in biology has the potential to modulate biological functions. Here we merge wireless nano-electrochemical tools with cancer cells for control over electron transfer to trigger cancer cell death. Gold bipolar nanoelectrodes functionalized with redox-active cytochrome c and a redox mediator zinc porphyrin are developed as electric-field-stimulating bio-actuators, termed bio-nanoantennae. We show that a remote electrical input regulates electron transport between these redox molecules, which results in quantum biological tunnelling for electron transfer to trigger apoptosis in patient-derived cancer cells in a selective manner. Transcriptomics data show that the electric-field-induced bio-nanoantenna targets the cancer cells in a unique manner, representing electrically induced control of molecular signalling. The work shows the potential of quantum-based medical diagnostics and treatments.

Dark-field spectroscopy: development, applications and perspectives in single nanoparticle catalysis

Dark-field microscopy (DFM) is an effective method to detect the scattering signal from single nanoparticles. This technique could break through the 200 nm limit resolution of ordinary optical microscopes. It even can observe the submicron particles of 20-200 nm. Moreover, from 2000, DFM was coupled with a spectrometer to measure the scattering spectra of single silver nanoparticles. Then, dark-field spectroscopy becomes a very important plasmon spectroscopy technique for single nanoparticles. Usually, plasmonic nanoparticles are the major research target, because they have unique optical properties due to their localized surface plasmon resonance (LSPR), which can be influenced by many factors, such as composition, size, morphology, the refractive index of the surrounding medium etc. When surface chemical reactions occur on a single nanoparticle, it could induce the variation of these factors. Then, the structure-activity relationship for these nanoparticle catalysts can be studied at a single nanoparticle level and in real time. This review mainly summarized the development of dark-field spectroscopy, spectrometers, light sources, and other accessories, which greatly improved the imaging capabilities of dark-field spectroscopy. Meanwhile, the applications of dark-field spectroscopy in single-particle catalysis such as chemocatalysis, photocatalysis, electrocatalysis and biocatalysis are also reviewed.

Analysis of the electron transfer properties of carbon quantum dots on gold nanorod surfaces via plasmonic resonance scattering spectroscopy

Carbon quantum dot wrapped gold nanorods were fabricated on an ITO electrode surface via electrostatic interactions. The electron transfer properties of carbon quantum dots on gold nanorod surfaces were systematically investigated by plasmonic resonance scattering spectroscopy.

Imaging the chemical activity of single nanoparticles with optical microscopy

Chemical activity of single nanoparticles can be imaged and determined by monitoring the optical signal of each individual during chemical reactions with advanced optical microscopes. It allows for clarifying the functional heterogeneity among individuals, and for uncovering the microscopic reaction mechanisms and kinetics that could otherwise be averaged out in ensemble measurements.

Single plasmonic nanoparticles as ultrasensitive sensors

In this mini review, we will provide a brief introduction focusing on the current applications of single plasmonic nanoparticle-based sensors using DFM, including the detection of molecules, the real-time monitoring of chemical/electrochemical reactions and the imaging of living cells.

Color-coded imaging of electrochromic process at single nanoparticle level

Electrochromic materials have attracted increasing attention in the field of smart devices and energy economy due to their excellent reversible chromic properties. Investigating an electrochromic process at the nano-scale is beneficial to the development of functional nano-devices exploiting chromophores. In this study, a new method for real-time imaging of an electrochromic process at the single nanoparticle level is developed based on an ultra-sensitive plasmon resonance energy transfer (PRET) technique. The scattering light intensity of nanoparticles is applied to reveal energy transfer from nanoparticles to chromophores modulated by an electrochromic reaction. This PRET-based technique achieves the detection of hundreds of molecules on the surface of a single nanoparticle. Furthermore, a color-coded amplifying method has been introduced for high-throughput, converting light intensity into easily recognized colors via the Matlab program. Compared with traditional electrochemical imaging techniques, this facile and rapid approach using optical techniques to characterize a real-time electrochemical process significantly enhances detection sensitivity, time and spatial resolution. Notably, the obtained electrochromic behavior of chromophores on a single nanoparticle is in good agreement with the simulated cyclic voltammetry (CV) curves on a nano-electrode. Therefore, this study provides a promising way to simultaneously monitor electrochromic reactions on single nano-electrodes with high-throughput.

Plasmon resonance scattering at perovskite CH3NH3PbI3 coated single gold nanoparticles: evidence for electron transfer

We demonstrate the electron transfer between gold nanoparticles and perovskite CH₃NH₃PbI₃ at a single nanoparticle level by plasmon resonance Rayleigh scattering spectroscopy.