A-HKU705/21

Van der Waals Heterostructures Controlled by Electromagnetic Cavity Resonators (CaVdW)

Hong Kong Principal Investigator: Professor W. Yao (The University of Hong Kong)

French Principal Investigator: Professor Cristiano Ciuti (Université de Paris)

The control of the electronic properties of solids is one of the main challenges of condensed matter physics. In recent years, 2D materials and their van der Waals heterostructures have sparked a tremendous interest for their tunable physical behavior associated with the electron’s quantum degrees of freedom including spin, valley and layer pseudospin. New opportunities to control their properties are emerging thanks to enhanced light-matter coupling enabled by the novel designs of optical microcavities, and terahertz electromagnetic resonators such as split-ring resonators with deep-subwavelength modal confinement and giant vacuum fields. With the ultrastrong light-matter coupling, the microcavities and nanoplasmonic resonators can modify not only the optical response of 2D materials, but also their transport properties even in the absence of illumination. The general goal of this project is to study novel electronic systems in van der Waals layered structures and their control by the coupling to deep-subwavelength electromagnetic resonators and microcavities without or with illumination. This French-Hong Kong joint project would explore a cutting-edge research field and create synergy by enhancing complementary expertise of two experimental groups and two theoretical teams.

 

A-CUHK404/21

Electrically-Excited Chiral Plasmonic NanoCavities

Hong Kong Principal Investigator: Prof WANG, Jianfang (Physics/ The Chinese University of Hong Kong)

French Principal Investigator: Prof BOER-DUCHEMIN, Elizabeth (Institut des Sciences Moléculaires d’Orsay (ISMO) / CNRS Université Paris-Saclay)

There is a type of matter that has two spatial structures. They look exactly the same, but they cannot overlap, like the left and right hands. Such matter is called chiral materials. Chiral materials widely exist in nature and are an integral part of our life, such as proteins and nucleic acids. A “left-handed” structure preferentially scatters or absorbs the “left-handed” circularly polarized light, and vice versa. The chiral structures therefore have a specific “chiroptical response”. The chirality can be detected by optical means. However, the chiroptical response in most cases is very weak. An approach for increasing the chiroptical response would be a breakthrough for many applications in biology, chemistry, and physics.

When a noble metal nanoparticle is deposited on metal substrates, a special plasmonic structure is formed, namely the “nanoparticle-on-a-mirror” structure. There is a nanoscale gap between the nanoparticle and the substrate to form a nanocavity. Under illumination, a large amount of electromagnetic energy is confined in the nanocavity. The main idea of this project is thus to apply this principle to chiral plasmonic cavities and thus enhance the chiral interaction between light and matter. Such a chiral nanocavity will be made by depositing a chemically synthesized gold nanoparticle that has a chiral structure on a thin (0.5–2 nm) insulating spacer layer on top of a metal film. This will be the first time to study this chiral nanocavity by optical means.

In addition to optical means, this project also uses electrical means to study the optical properties of the “chiral nanoparticle-on-a-mirror” structure. In the future optoelectronic nanodevices, a local electronic excitation is necessary. Working with this long-term goal in mind, we will use inelastic tunneling electrons to locally excite the “chiral nanoparticle-on-a-mirror” samples. The chiral nanoparticles will be contacted with the conducting tip of an atomic force microscope to form an electrical circuit. The chiral nanocavity will be a tunneling junction. Under polarization, some electrons will undergo inelastic tunneling, and the lost energy can excite the chiral plasmon mode. This mode will then radiate outward in the form of light with a specific “handedness”. In order to demonstrate the possible application of the expected enhanced chiral response in the “chiral nanoparticle-on-a-mirror” geometry, a monolayer of a transition metal dichalcogenide (TMDC) material will be placed in the chiral nanocavity. TMDC monolayers are two-dimensional (2D) semiconductors, which are being considered as the core materials of a new computational paradigm: “valleytronics”. In TMDC monolayers, electrons from different valleys emit light with different circular polarizations when recombining with holes. Valleytronics is therefore closely related to optical chirality. In a “handed” chiral plasmonic nanocavity, the emission from a particular valley is expected to be further enhanced.

 

A-PolyU502/21

Design, Development of New Synthetic Strategies and Evaluation of Antimicrobial N-heterocycles

Hong Kong Principal Investigator: Dr Cong MA (The Hong Kong Polytechnic University)

French Principal Investigator: Dr Nicolas Blanchard (Université de Haute-Alsace)

This research aims to design and synthesize complex N-heterocycles using innovative methodologies for application in antimicrobial agent discovery. Antibiotic-resistant bacteria are one of the major causes for the re-spread of infectious diseases, which becomes a real crisis worldwide. Therefore, the identification of novel antimicrobial agents with unprecedented pharmacological mechanisms is urgently required.

We previously developed a series of first-in-class antimicrobial compounds targeting the protein-protein interactions between bacterial transcription factors NusB and NusE, responsible for bacterial rRNA synthesis. This chemical series of compounds was named “nusbiarylins” to reflect the target NusB and the biarylic structure. These compounds demonstrated excellent antimicrobial activity comparable to commercially available antibiotics against a panel of WHO priority pathogens, including clinical isolated methicillin-resistant Staphylococcus aureus (MRSA).

Remarkably, when we incorporated N-heterocycles such as the indole and benzimidazole moieties into the biarylic structure of nusbiarylins, the antimicrobial activity was drastically improved. The results encouraged us to explore further possibilities of structural diversification for the lead optimization in this project. Our collaborators in France and Hong Kong are developing novel and efficient methods for complex N-heterocycle synthesis. We hypothesize that these methodologies can be used for generating new series of antimicrobial agents potential for drug development.

Based on our expertise in organic chemistry, medicinal chemistry, microbiology, and pharmaceutical sciences, we expect to successfully complete this research. These new N-heterocycle antimicrobial agents obtained by structure-based drug design with a unique mechanism of action will provide exclusive therapeutic potentials against antibiotic-resistant bacterial infectious diseases.