Carbon-incorporated Zinc oxide (ZnO-C) nanowires demonstrate an enhanced variety of post-fabrication modification pathways such as electron beam treatment. Using localized low energy electron irradiation in a scanning electron microscope, axial heterostructures with varying defect fluorescence properties were engineered with sub-micron precision in ZnO-C nanowires. The electron-induced modification of the defect fluorescence of four types of nanowires, differentiated by their carbon content and defect fluorescence polarization, were characterized. Spatially extensive fluorescence quenching was observed in nanowires with lower carbon content. In higher carbon content nanowires, localized fluorescence intensity enhancement and color conversion from red to green was observed. In nanowires with an additional polarized emission component, the polarized component exhibited localized quenching independent of the unpolarized component. Additionally, electron beam induced deposition of amorphous carbon was achieved on ZnO-C NWs and found to be controllable by electron irradiation parameters. X-ray photoelectron spectroscopy measurements conducted on nanowire array samples implied that electron irradiation caused the replacement of zinc with carbon atoms. Finally, a method of visualizing electron trajectories through the nanowire by imaging the electron-enhanced fluorescence of surface contamination on the substrate was demonstrated and used to validate trajectories simulated by Monte Carlo simulations.

Defect fluorescence from high aspect ratio semiconductor nanowires typically displays a weak polarization parallel to the nanowire’s long axis due to dielectric mismatch in high aspect ratio media. Instead, anomalous 2.2 eV defect fluorescence distinctly polarized perpendicular to the nanowire is observed and measured from carbon-incorporated zinc oxide nanowires. These observations are significant because polarized defect emissions with consistent polarization on a mesoscopic scale are uncommon. Through a systematic study and comparison of experimental results with density functional theory calculations, an oriented defect complex comprising carbon substituting on an oxygen site and an oxygen vacancy (C_O-V_O) is deduced to be responsible for the anomalous yellow fluorescence, demonstrating a method for relating atomic-scale defect geometry to mesoscopic properties. The anomalous emission can appear in both green- and red-fluorescing nanowires grown with different carbon concentrations, verifying the independence and uniqueness of the 2.2 eV emission. This allows for polarization-dependent emission wavelength selection from a single nanowire.

Recovered carbon black (rCB), a very economical and abundance source of material, is transformed into dazzling multicolour fluorescence and visual display for the first time by way of a scanning focused laser treatment. This laser-initiated process is both straightforward and versatile, catering to both micro- and macro-scopic patterning with the sample in ambient or helium environment. The observed phenomenon is attributed to both chemical and structural induced colouration of rCB powder. Chemically, carbon infusion of oxidised metal occurs when photothermal reaction takes place in ambient. After laser modification with the sample in helium environment, the powder not only fluoresces due to sulphur impurities, control annealing of these powders results in formation of periodic arrangements of carbon nanoparticles. The periodicity of these arrangement falls within the range of visible wavelength, hence contributing to the visually observable rainbow coloured rCB flakes. The patterned sample is also transferrable using PDMS stamps. This in turn broadens the application of this material in flexible electronic devices/displays. Photocurrent measurements show most significant enhancement under yellow light illumination. Furthermore, in the presence of an applied potential, the fluorescence detected from the sample can easily be switched off. All in all, we present a simple process to add multiple functionalities to a material that is both inexpensive and sustainable.

We demonstrate a facile and effective approach to significantly improve the photoluminescence of bulk MoS₂ via laser thinning followed by gold particle decoration. Upon laser thinning of exfoliated bulk MoS₂, photoluminescence emerges from the laser-thinned region. After further treatment with an AuCl₃ solution, gold particles self-assemble on the laser-thinned region and thick edges, further increasing the fluorescence of bulk MoS₂ 28 times and the Raman response 3 times. Such fluorescence enhancement can be attributed to both surface plasmon resonance and p-type doping induced by gold particles. The combination of laser thinning and AuCl₃ treatment enables the functionalization of bulk MoS₂ for optoelectronic applications. It can also provide a viable strategy for mask-free and area-selective p-type doping on single MoS₂ flakes.

We employ optical pump-terahertz probe spectroscopy to investigate the composition-dependent photoconductivity in ternary CdS_xSe_1–x nanobelts. The observed carrier dynamics of CdS nanobelts display much shorter lifetime than those of ternary CdS_xSe_1–x nanobelts. This indicates the implementation of CdS nanobelts as ultrafast switching devices with a switching speed potentially up to 46.7 GHz. Surprisingly, ternary CdS_xSe_1–x nanobelts are found to exhibit much higher photoconductivity than binary CdS and CdSe. This is attributed to the higher photocarrier densities in ternary compounds. In addition, the presence of Se in samples resulted in prominent CdSe-like transverse optical (TO) phonon modes due to electron–phonon interactions. The strength of this mode shows a large drop upon photoexcitation but recovers gradually with time. These results demonstrated that growth of ternary nanostructures can be utilized to alleviate the high surface defect density in nanostructures and improve their photoconductivity.

With self-assembly being an efficient and often preferred process to build micro- and nano-materials into ordered macroscopic structures, we report a simple method to assemble monolayer graphene onto densified vertically aligned carbon nanotube (CNT) micropillars en route to unique functional three-dimensional microarchitecture. This hybrid structure provides new means of studying strain induced in suspended graphene. The strain induced could be controlled by the size and number of supporting microstructures, as well as laser-initiated localised relaxation of the graphene sheet. The assembled structure is also able to withstand high-energy electron irradiation with negligible effect on the electrical properties of the hybrid system. The hybrid system was further functionalised with quantum dots on the CNTs with the assembled top graphene layer as a transparent electrode. Significant improvements in photocurrent were achieved in this system.