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Composites or hybrid materials offer diverse properties not achievable in pure materials. Here we critically review the interesting and controllable fluorescence and photothermal properties of diverse hybrid materials containing up-conversion nanoparticles (UCNPs). These hybrids couple plasmons, photonic crystals, bio-surfaces, and two dimensional (2D) materials to the UCNPs, offering optical non-linearity, and enable effective photo-electro-thermal control leading to new light and heat driven applications. Among the light driven applications, coupling of UCNPs with graphene and molybdenum disulfide (MoS2) enables photodetectors with better photoresponse, and broader spectral range not accessible to individual components. Irradiated MoS2 coupled-UCNPs is a new paradigm in resistive random access memory devices. Conjugation of graphene and perovskites, with the UCNPs, have led to novel optical limiting phenomenon and better solar cells. Examples of new opportunities offered by UCNPs in heat driven applications are photothermal water desalination using solar daylight and photothermal disintegration of fat droplets in obesity treatment. Phonons, manifesting as heat, can also be utilized to enhance fluorescence and translate to high sensitivity nanothermometers. This review covers fundamentals, and applications of the new UCNP-enabled class of hybrid materials in energy harnessing, light sources and detectors, memory devices, nanothermometers, desalination, intracellular pH sensing, and cancer theranostics.

Recent years have witnessed successful applications of non-thermal plasmas (NTPs) as efficient and flexible tools for direct conversion of liquid alcohols into higher-value energy carriers at mild or even near-room-temperature conditions. Better understanding of the fundamental physical properties of the liquid alcohol discharges is needed for development and optimization of NTP-based applications. Here we investigate the discharge characteristics of a plasma-based liquid ethanol conversion under different process parameters and reveal the general trends of the discharge behavior. Two discharge modes, namely the self-pulsed and direct current (DC) modes, are sustained during the in-liquid discharge. These two modes can be easily interchanged and flexibly controlled by adjusting the processing parameters. The behavior of the bubbles generated during the discharge plays an important role in the transition between the discharge modes. When the discharge is sustained with the diffusion and floating of the bubbles, the DC mode is observed. Otherwise, the discharge develops into the pulse mode. The production rates and composition of the gaseous products are also shown to depend on the discharge modes.

Highly size-controllable synthesis of free-standing perfectly crystalline silicon carbide nanocrystals has been achieved for the first time through a plasma-based bottom-up process. This low-cost, scalable, ligand-free atmospheric pressure technique allows fabrication of ultra-small (down to 1.5 nm) nanocrystals with very low level of surface contamination, leading to fundamental insights into optical properties of the nanocrystals. This is also confirmed by their exceptional photoluminescence emission yield enhanced by more than 5 times by reducing the nanocrystals sizes in the range of 1-5 nm, which is attributed to quantum confinement in ultra-small nanocrystals. This method is potentially scalable and readily extendable to a wide range of other classes of materials. Moreover, this ligand-free process can produce colloidal nanocrystals by direct deposition into liquid, onto biological materials or onto the substrate of choice to form nanocrystal films. Our simple but efficient approach based on non-equilibrium plasma environment is a response to the need of most efficient bottom-up processes in nanosynthesis and nanotechnology., Funding Agencies|Royal Society International Exchange Scheme [IE120884]; Leverhulme International Network [IN-2012-136]; EPSRC [EP/K022237/1, EP/M024938/1]; EU-FP7 [606889]; University of Ulster Vice-Chancellor Studentship; EU [606889]; CSIRO; Australian Research Council; School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology