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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - SCHiMAT (Silicon Cluster based Hierarchical photocatalysts produced by MATrix assembly cluster source)

Teaser

Summary

Photocatalysis is important for solving the worldwide energy shortage and environmental pollution issues. Recently, nano-size materials are considered to be promising catalysts. In particular, size controlled clusters/nanoparticles/QDs show tunable emissions/absorption from near infrared to blue wavelength, making them promising candidates as photocatalysts. However, the research on the metal/dielectric clusters based photocatalysts is still slow progress due to lacking of methods of fabrication of nano-size clusters with precision and in large quantities. In SCHiMAT, the luminescent, photoelectric and photocatalytic properties of metal/dielectric clusters with precisely controllable size and high production, which produced by â€œMatrix Assembly Cluster Sourceâ€ (MACS), have been systemically studied. Based on that, this project have entailed the design of a novel kind of hierarchical structure, which involves the choice of large size semiconductor nanoparticles (SiO2, Al2O3, ZrO2, TiO2 CeO2 and ZnO NPs) and distribution modulation of the small clusters on the large size support, to largely enhance the optical response and photocatalytic efficiency of the small size QDs. This project could open a promising new route to using cluster/QDs as visible-light absorber for solar energy conversion. The project combined ER and host supervisorâ€™s expertise in nanocluster, photonics, catalysis research, and equiped the ER to carry out cutting edge research in cluster-based nanomaterials and photocatalysis.
The overarching aim of this project is to apply a new type of cluster source, the â€œMatrix Assembly Cluster Sourceâ€ (MACS) (which has been recently developed by Prof. Richard Palmer at the University of Birmingham), to perform high-flux deposition of metal/dielectric clusters with controllable size. Based on that, we further aim to design and prepare cluster based hierarchical structures for highly efficient photocatalysis.
Not limited to the proposed research objectives, during the project we further enriched the research content, which including:
(1) develop novel hierarchical nanostructures based on gas-phase cluster beam deposition for highly sensitive surface enhenced Raman scattering (SERS) detection.
(2) hydrogen sensor based on Pd nanoparticle arrays.
(3) solar energy harvesting nanostructures.

Work performed

The Marie SkÅ‚odowska-Curie fellowship (SCHiMAT) significantly further enhanced my career in high-level research. The main research achievements and results during this period are shown as following and in :
1. Hierarchical plasmonic nanostructure for field enhancement and molecule detection. By exploiting the equivalence of light propagation between spatio-temporal geometries and materials with variation of refractive index, we designed and characterised a SERS device based on warped spaces that strongly enhance broadband electromagnetic energy over a relatively large spectral region. These results have been published in:
[1] Nature Communications, 2018, 9, 5428.
[2] Chinese Journal of Chemical Physics, 2019, Just Accepted.
I further developed a novel super-hydrophobic hierarchical plasmonic nanostructure for molecule delivery and detection by combining super-hydrophobic artificial surfaces and nanoplasmonic structures, that few molecules can be localized and detected even at attomolar (1e-18 M) concentration. Moreover, the detection can be combined with fluorescence and Raman spectroscopy, such that the chemical signature of the molecules can be clearly determined. (Paper in preparation)
2. Metallic nanoparticle array based gas sensors. We developed a novel H2 sensor based on closely spaced metallic Pd nanoparticle arrays. We further demonstrated a feasible approach to fabricate gas sensors with selectivity by coating a polymeric membrane (PMMA) for gas separation. And we also have realized an optically transparent and flexible H2 sensor by depositing a Pd nanoparticle array onto a PET substrate. The H2 responsiveness showed no performance degradation after 500 bending cycles, showing good flexibility, robust electromechanical properties, and stable H2-sensing behavior. In addition, the effect of strain on the H2-sensing behaviors was also investigated. These results have been published in:
[3] ACS Applied Materials & Interfaces, 2017, 09, 27193-27201.
[4] Sensors and Actuators A: Physical, 2018, 272, 161-169.
[5] ACS Applied Materials & Interfaces, 2018, 4, 5406-5409.
3. Plasmonic nanostructures for broadband light absorption and energy harvesting. We achieved to manipulate a disordered plasmonic system, realising the transition from a broadband absorption to tunable reflection through a deterministic control of the coupling to an external cavity. Not limited to the significance in the physics, the disordered plasmonic system provides a novel platform for various practical application including structural colour patterning and solar energy harvesting. These results have been submitted to
[6] Nature Communications (2019, under review)
Instead of a direct mathematical abstract, we design a fractal structure from the outline of a leaf and apply it for solar energy harvesting. Combined with the feature of self-similarity, the bio-inspired fractal geometry can turn an 10 nm thick gold to an effective absorber, especially at the near infrared region containing a large amount of solar energy. These results have been published in:
[7] Nanophotonics, 2019, DOI: https://doi.org/10.1515/nanoph-2019-0104.
4. Plamonic nanostructure for photocatalysis. we presented a design of TiO2 nanorod arrays decorated with Au, Ag, Ru, Pd, Pt, TiN and Si nanoclusters directly synthesized through successive gas-phase cluster beam deposition. The present design of cluster-decoration on the TiO2 nanorods shows much higher visible and ultraviolet light absorption response, which leads to remarkably enhanced photocatalytic activities on both the dye degradation and solar water splitting performance. (Papers in preparation)

Final results

This research has applied a new tool to the large-scale fabrication of nanoclusters and cluster-based photocatalysts and sensors. New methodologies and fundamental insights in this area could have a significant economic and environmental impact.
In the project, we have achieved broadband single molecule SERS detection, highly sensitive gas-sensor and hight efficient photocatalysis based on heirarchical nanostructures prepared by gas-phase cluster beam deposition. Not limited to the sensing and photocatalysis, the developed nanomaterials could boost the development of many different applications of crucial importance in many fields, including nonlinear harmonic generation, plasmonic laser and hot-electrons, where new structures can be engineered by equivalent systems where the existence of specific media is substituted by suitably defined warped spatial geometries. Mostly importantly, the nanosensors deceloped in this project have wide commercial prospects, which is highly desirable in a plethora of applications, and in particular for those related to real-time environmental monitoring and pathogens and protein recognition for disease diagnosis.