Influence of morphology on electrical and optical properties of graphene/Al-doped ZnO-nanorod composites

Electrochemical investigation of carbon paper/ZnO nanocomposite electrodes for capacitive anion capturing

In this work, we demonstrate an effective anion capturing in an aqueous medium using a highly porous carbon paper decorated with ZnO nanorods. A sol-gel technique was first employed to form a thin and compact seed layer of ZnO nanoparticles on the dense network of carbon fibers in the carbon paper. Subsequently, ZnO nanorods were successfully grown on the pre-seeded carbon papers using inexpensive chemical bath deposition. The prepared porous electrodes were electrochemically investigated for improved charge storage and stability under long-term operational conditions. The results show effective capacitive deionization with a maximum areal capacitance of 2 mF/cm², an energy consumption of 50 kJ per mole of chlorine ions, and an excellent long-term stability of the fabricated C-ZnO electrodes. The experimental results are supported by COMSOL simulations. Besides the demonstrated capacitive desalination application, our results can directly be used to realize suitable electrodes for energy storage in supercapacitors.

Unconventional plasmonic sensitization of graphene in mid-infrared

Light-matter interaction in graphene can be engineered and substantially enhanced through plasmonic sensitization, which has led to numerous applications in photodetection, sensing, photocatalysis and spectroscopy. The majority of these designs have relied on conventional plasmonic materials such as gold, silver and aluminum. This limits the implementation of such devices to the ultraviolet and visible regimes of the electromagnetic spectrum. However, for many practical applications, including those relevant to security and defense, the development of new strategies and materials for sensing and detection of infra red (IR) light is crucial. Here we use surface enhanced Raman spectroscopy (SERS), for direct visualization and estimation of enhanced light-matter interaction in graphene in the mid-IR regime, through sensitization by an unconventional plasmonic material. Specifically, we fabricate a hybrid device consisting of a single layer graphene and a two-dimensional array of nanodiscs of aluminum doped zinc oxide (AZO), which is a highly doped semiconductor, exhibiting plasmonic resonance in the mid-IR. We find that the enhancement in the SERS signal of graphene is of similar magnitude to what has been achieved previously in the visible using conventional plasmonic materials. Our results establish the potential of such hybrid systems for graphene-based optical and optoelectronic applications in the mid-IR.

2D/3D graphene on h-BN interlayer-silicon solar cell with ZnO:Al buffer layer and enormous light captivation using Au/Ag NPs

In this paper, systematic design and analysis of thin-film graphene-silicon solar cells with the addition of an anti-reflection coating (ARC), hexagonal boron nitride (h-BN) interlayer and decorated with Au/Ag NPs infused in rear ZnO:Al buffer layer is reported. The 3D NPs are located on the top and rear side of the solar cell. Initially, we simulated a reference 2D graphene-silicon solar cell with highest simulated short circuit current density (Jsc) 30mA/ cm² and power conversion efficiency (PCE) of 10.65%. Using 2D and 3D full vectorial finite element method (FVFEM) simulations, we significantly improved the Jsc by 6.2mA/ cm² from 30mA/cm² to 36.21mA/cm² and PCE from 10.93% to 12.03%. We utilized a patterned graphene sheet with small nanoholes to increase surface and optical conductivity. Plasmonic NPs embedded in a graphene-silicon solar cell to increase plasmonic resonance effects is investigated. The 3D position of the patterned graphene, rear buffer layer stack, size, shape, and periodicity of NPs were well-controlled and analyzed under certain parametric variation conditions. Ag NPs located inside textured ZnO:Al detached to metal contact and small periodic Au NPs decorated beneath a h-BN interlayer lead to highly efficient light confinement and increase photon current generation. The proposed device exhibits 12.03% PCE, maximum light absorption over 80% and high overall quantum efficiency (QE). Furthermore, this structure offers major light trapping advantages, including significant EM light propagation throughout the solar cell structure.

Graphene-based plasmonic nanocomposites for highly enhanced solar-driven photocatalytic activities

High-efficiency photocatalysts are crucial for the removal of organic pollutants and environmental sustainability. In the present work, we report on a new low-temperature hydrothermal chemical method, assisted by ultrasonication, to synthesize disruptive plasmonic ZnO/graphene/Ag/AgI nanocomposites for solar-driven photocatalysis. The plasmonic nanocomposites were investigated by a wide range of characterization techniques, confirming successful formation of photocatalysts with excellent degradation efficiency. Using Congo red as a model dye molecule, our experimental results demonstrated a photocatalytic reactivity exceeding 90% efficiency after one hour simulated solar irradiation. The significantly enhanced degradation efficiency is attributed to improved electronic properties of the nanocomposites by hybridization of the graphene and to the addition of Ag/AgI which generates a strong surface plasmon resonance effect in the metallic silver further improving the photocatalytic activity and stability under solar irradiation. Scavenger experiments suggest that superoxide and hydroxyl radicals are responsible for the photodegradation of Congo red. Our findings are important for the fundamental understanding of the photocatalytic mechanism of ZnO/graphene/Ag/AgI nanocomposites and can lead to further development of novel efficient photocatalyst materials.

High-efficiency of plasmonic ZnO/graphene/Ag/AgI nanocomposites for solar-driven photocatalysis activities.