March 2023

Publication - Hot Carrier Cooling and Trapping in Atomically Thin WS2 Probed by Three-Pulse Femtosecond Spectroscopy

Transition metal dichalcogenides (TMDs) have shown outstanding semiconducting properties which make them promising materials for next-generation optoelectronic and electronic devices. These properties are imparted by fundamental carrier–carrier and carrier–phonon interactions that are foundational to hot carrier cooling. Recent transient absorption studies have reported ultrafast time scales for carrier cooling in TMDs that can be slowed at high excitation densities via a hot-phonon bottleneck (HPB) and discussed these findings in the light of optoelectronic applications. However, quantitative descriptions of the HPB in TMDs, including details of the electron–lattice coupling and how cooling is affected by the redistribution of energy between carriers, are still lacking. Here, we use femtosecond pump–push–probe spectroscopy as a single approach to systematically characterize the scattering of hot carriers with optical phonons, cold carriers, and defects in a benchmark TMD monolayer of polycrystalline WS2. By controlling the interband pump and intraband push excitations, we observe, in real-time (i) an extremely rapid “intrinsic” cooling rate of ∼18 ± 2.7 eV/ps, which can be slowed with increasing hot carrier density, (ii) the deprecation of this HPB at elevated cold carrier densities, exposing a previously undisclosed role of the carrier–carrier interactions in mediating cooling, and (iii) the interception of high energy hot carriers on the subpicosecond time scale by lattice defects, which may account for the lower photoluminescence yield of TMDs when excited above band gap.

Image is copied from https://doi.org/10.1021/acsnano.2c10479. For more details, please find our publication here: Hot Carrier Cooling and Trapping in Atomically Thin WS2 Probed by Three-Pulse Femtosecond Spectroscopy

January 2023

 Publication - A sprayed graphene transistor platform for rapid and low-cost chemical sensing

We demonstrate a novel and versatile sensing platform, based on electrolyte-gated graphene FETs, for easy, low-cost and scalable production of chemical sensor test strips. The Lab-on-PCB platform is enabled by low-boiling, low-surface-tension sprayable graphene ink deposited on a substrate manufactured using a commercial printed circuit board process. We demonstrate the versatility of the platform by sensing pH and Na⁺ concentrations in an aqueous solution, achieving a sensitivity of 143 ± 4 μA per pH and 131 ± 5 μA per log₁₀Na⁺, respectively, in line with state-of-the-art graphene chemical sensing performance.

Image is copyed from: DOI https://doi.org/10.1039/D2NR05838C3. For more details, please find our publication here: A sprayed graphene transistor platform for rapid and low-cost chemical sensing.

December 2022

Benji presents his GFET research on MRS 2022

One of our senior PhD candidates, Benji Fenech-Salerno, attended MRS 2022 in Boston, USA earlier this month, where he was presenting his latest progress on 2D-material chemical sensors. He enjoyed the conference with fatanstic speeches and academic conversations very much.

Christmas dinner 2022

We had a warm and happy Christmas dinner gathering at Balans West on 9 December, 2022. Very nice dishes! After pandemic, it is so nice to have everyone in person and enjoy time together over meal!

Many thanks to Shuwei for organizing this fantastic event!

 Publication - Review of recent progress on free-standing supercapacitors

We summarize the recent progress on free-standing supercapacitors from new methods to create free-standing electrodes to novel applications for these devices, together with a detailed discussion and analysis on their electrochemical performance and physicochemical and mechanical properties. Furthermore, the potential directions and prospects of future research in developing free-standing supercapacitors are proposed.

Image is copyed from: Latham KG, Edathil AA, Rezaei B, Liu S, Nguyen S, Keller SS, Torrisi F, Greenhalgh ES, Titirici Met al., 2022, Challenges and opportunities in free-standing supercapacitors research, APL Materials, Vol: 10, Pages: 110903-110903.

For more details, please find our publication here: Challenges and opportunities in free-standing supercapacitors research.

November 2022

Chengning wins best student paper on E-textile 2022

Our very own Chengning Yao was awarded the best student paper at E-textiles 2022 Conference in Nottingham in November 2022! Chengning gave her 2-minute pitch and a wonderful poster presentation highlighted some of her key findings from her PhD work on the thermal conductivity of h-BN-assited composite. 

July 2022

Benji wins 1st at Chemistry PG symposium 2022

Congratulations to 1 of our PhD students Benji Fenech Salerno, who was awarded 1st prize in the Materials & Molecular Design Session in the Departmental of Chemistry PG Symposium in July at Imperial College London for his presentation showcasing our latest progress in biosensor research!

In his research, he demonstrated printed graphene field effect transistor (GFET) biosensors for the detection of multiple analytes, using reliable liquid phase exfoliation and repeatable printing technique.