Sunxuehao

This work provides a comprehensive analysis of ultrafast chiroptical responses in planar plasmonic nano-oligomers with facile reversibility. The polarimetric measurements demonstrate the transient helicity-resolved optical transitions in chiral nanoplasmonics in an all-optical setting, providing a framework for future applications of ultrafast switching and optical logic circuits in nanophotonics and quantum optics.

Abstract

Ultracompact chiral plasmonic nanostructures with unique chiral light–matter interactions are vital for future photonic technologies. However, previous studies are limited to reporting their steady-state performance, presenting a fundamental obstacle to the development of high-speed optical devices with polarization sensitivity. Here, a comprehensive analysis of ultrafast chiroptical response of chiral gold nano-oligomers using time-resolved polarimetric measurements is provided. Significant differences are observed in terms of the absorption intensity, thus hot electron generation, and hot carrier decay time upon polarized photopumping, which are explained by a phenomenological model of the helicity-resolved optical transitions. Moreover, the chiroptical signal is switchable by reversing the direction of the pump pulse, demonstrating the versatile modulation of polarization selection in a single device. The results offer fundamental insights into the helicity-resolved optical transitions in photoexcited chiral plasmonics and can facilitate the development of high-speed polarization-sensitive flat optics with potential applications in nanophotonics and quantum optics.

Facet-engineered Cu₂O nanostructures are synthesized by wet-chemical methods for electrocatalytic hydrogen evolution reaction (HER). Operando Raman spectroscopy and ex situ characterization techniques show that Cu₂O is reduced during HER. Incident photon-to-current efficiency measurements combined with ab initio nonadiabatic molecular dynamics simulations demonstrate the hot-electron injection from Cu dendrites to Cu₂O facilitates the plasmon-enhanced electrocatalytic HER activity.

Abstract

Herein, facet-engineered Cu₂O nanostructures are synthesized by wet chemical methods for electrocatalytic HER, and it is found that the octahedral Cu₂O nanostructures with exposed crystal planes of (111) (O-Cu₂O) has the best hydrogen evolution performance. Operando Raman spectroscopy and ex-situ characterization techniques showed that Cu₂O is reduced during HER, in which Cu dendrites are grown on the surface of the Cu₂O nanostructures, resulting in the better HER performance of O-Cu₂O after HER (O-Cu₂O-A) compared with that of the as-prepared O-Cu₂O. Under illumination, the onset potential of O-Cu₂O-A is ca. 52 mV positive than that of O-Cu₂O, which is induced by the plasmon-activated electrochemical system consisting of Cu₂O and the in-situ generated Cu dendrites. Incident photon-to-current efficiency (IPCE) measurements and the simulated UV–Vis spectrum demonstrate the hot electron injection (HEI) from Cu dendrites to Cu₂O. Ab initio nonadiabatic molecular dynamics (NAMD) simulations revealed the transfer of photogenerated electrons (27 fs) from Cu dendrites to Cu₂O nanostructures is faster than electron relaxation (170 fs), enhancing its surface plasmons activity, and the HEI of Cu dendrites increases the charge density of Cu₂O. These make the energy level of the catalyst be closer to that of H⁺/H₂, evidenced by the plasmon-enhanced HER electrocatalytic activity.

Nature Materials, Published online: 13 July 2023; doi:10.1038/s41563-023-01590-5

Robust near ultraviolet circularly polarized luminescence (CPL) materials have been developed for generating efficient circularly polarized electroluminescence (CP-EL). In their Research Article (e202300492), by adopting near ultraviolet CPL materials as emitters, hosts, or sensitizers, Zujin Zhao and co-workers report a simple and universal strategy for obtaining state-of-the-art CP-EL performances from various commercially available achiral luminescent materials.

A simple and portable Au-on-Au tip sensor was constructed to achieve specific, sensitive, and colorimetric detection of Salmonella typhimurium using an RNase H2-specific nucleic acid molecule derived from a random-sequence synthetic nucleic acid pool by in vitro selection.

Abstract

An Au-on-Au tip sensor is developed for the detection of Salmonella typhimurium (Salmonella), using a new synthetic nucleic acid probe (NAP) as a linker for the immobilization of a DNA-conjugated Au nanoparticle (AuNP) onto a DNA-attached thin Au layer inside a pipette tip. In the presence of Salmonella, RNase H2 from Salmonella (STH2) cleaves the NAP and the freed DNA-conjugated AuNP can be visually detected by a paper strip. This portable biosensor does not require any electronic, electrochemical or optical equipment. It delivers a detection limit of 3.2×10³ CFU mL⁻¹ for Salmonella in 1 h without cell-culturing or signal amplification and does not show cross-reactivity with several control bacteria. Further, the sensor reliably detects Salmonella spiked in food samples, such as ground beef and chicken, milk, and eggs. The sensor can be reused and is stable at ambient temperature, showing its potential as a point-of-need device for the prevention of food poisoning by Salmonella.

Through strong ligand-mediated interfacial energy control, this work demonstrates the continuous tuning of the AuNR (Au nanorod)-Cu₂O core–shell structure to Janus structures in hotdog, hammer, and dumbbell configurations. The high crystallinity and the physical separation of the Au and Cu₂O domains in dumbbell nanostructure, leading to superior photocatalytic degradation and effectively electrochemically catalyzed the CO₂ to ethanol products via a cascade reaction pathway.

Abstract

Precise structural control has attracted tremendous interest in pursuit of the tailoring of physical properties. Here, this work shows that through strong ligand-mediated interfacial energy control, Au-Cu₂O dumbbell structures where both the Au nanorod (AuNR) and the partially encapsulating Cu₂O domains are highly crystalline. The synthetic advance allows physical separation of the Au and Cu₂O domains, in addition to the use of long nanorods with tunable absorption wavelength, and the crystalline Cu₂O domain with well-defined facets. The interplay of plasmon and Schottky effects boosts the photocatalytic performance in the model photodegradation of methyl orange, showing superior catalytic efficiency than the AuNR@Cu₂O core–shell structures. In addition, compared to the typical core–shell structures, the AuNR-Cu₂O dumbbells can effectively electrochemically catalyze the CO₂ to C₂₊ products (ethanol and ethylene) via a cascade reaction pathway. The excellent dual function of both photo- and electrocatalysis can be attributed to the fine physical separation of the crystalline Au and Cu₂O domains.

Infections with antibiotic-resistant bacteria pose a major threat to human health and require fast and efficient diagnostic techniques. Here, localized surface plasmon resonance (LSPR) spectroscopy is used to detect an antimicrobial resistance gene, sulfhydryl variable β-lactamase (blaSHV), and also to distinguish clinically relevant single nucleotide polymorphism variants from the wild type. Due to high temporal measurement resolution, even kinetic evaluations of the binding events are performed.

Abstract

The development of rapid, simple, and accurate bioassays for the detection of nucleic acids has received increasing demand in recent years. Here, localized surface plasmon resonance (LSPR) spectroscopy for the detection of an antimicrobial resistance gene, sulfhydryl variable β-lactamase (blaSHV), which confers resistance against a broad spectrum of β-lactam antibiotics is used. By performing limit of detection experiments, a 23 nucleotide (nt) long deoxyribonucleic acid (DNA) sequence down to 25 nm was detected, whereby the signal intensity is inversely correlated with sequence length (23, 43, 63, and 100 nt). In addition to endpoint measurements of hybridization events, the setup also allowed to monitor the hybridization events in real-time, and consequently enabled to extract kinetic parameters of the studied binding reaction. Performing LSPR measurements using single nucleotide polymorphism (SNP) variants of blaSHV revealed that these sequences can be distinguished from the fully complementary sequence. The possibility to distinguish such sequences is of utmost importance in clinical environments, as it allows to identify mutations essential for enzyme function and thus, is crucial for the correct treatment with antibiotics. Taken together, this system provides a robust, label-free, and cost-efficient analytical tool for the detection of nucleic acids and will enable the surveillance of antimicrobial resistance determinants.

Light: Science & Applications, Published online: 25 April 2023; doi:10.1038/s41377-023-01092-8