Self-Assembled Hierarchical Nanostructures for High-Efficiency Porous Photonic Crystals

Abstract

The nanoscale modulation of material properties such as porosity and morphology is used in the natural world to mold the flow of light and to obtain structural colors. The ability to mimic these strategies while adding technological functionality has the potential to open up a broad array of applications. Porous photonic crystals are one such technological candidate, but have typically underachieved in terms of available materials, structural and optical quality, compatibility with different substrates (e.g., silicon, flexible organics), and scalability. We report here an alternative fabrication method based on the bottom-up self-assembly of elementary building blocks from the gas phase into high surface area photonic hierarchical nanostructures at room temperature. Periodic refractive index modulation is achieved by stacking layers with different nanoarchitectures. High-efficiency porous Bragg reflectors are successfully fabricated with sub-micrometer thick films on glass, silicon, and flexible substrates. High diffraction efficiency broadband mirrors (R≈1), opto-fluidic switches, and arrays of photonic crystal pixels with size<10 μm are demonstrated. Possible applications in filtering, sensing, electro-optical modulation, solar cells, and photocatalysis are envisioned.

Self-assembly of porous copper oxide hierarchical nanostructures for selective determinations of glucose and ascorbic acid

“…Interestingly, it was noted that, the copper-ion precursors were effectively controlling the self-assembly of CuO nanoparticles within the hierarchical structures. The induced-water hydrolysis of [Cu(NH 3 ) 4 2 converted to monoclinic CuO due to oxolation process at a relatively higher temperature without a trace of the subsequent annealing treatment in air (eqn (3)). Hence, the copper ions source can modify the subsequent precipitation process, which might affect the competition between thermodynamics and kinetics during the transformation of precursors, nucleation, growth and assembly of CuO nanostructures (see the following equations).…”

“…To date, hierarchical metal oxide micro-/nanostructures have attracted considerable attention, because of their technological and fundamental scientic importance and potential applications; including chemical and electrochemical sensing, catalysis, nanoelectronics and nanophotonics. [3][4][5][6] These hierarchical porous micro-/nanostructures offer minimized diffusion resistance, high surface area and good conductivity. 7 Therefore, numerous hierarchical metal oxides micro-/nanostructures have been recently reported.…”

“…These unique micro/nanostructures are then utilised to produce disposable screen-printed electrodes. Additive-free, large-scale production and simple fabrication strategy of hierarchical CuO micro-/nanostructures were developed via one-step hydrolysis of [Cu(NH 3 ) 4 …”

Hierarchically Structured Fullerene C70 Cube for Sensing Volatile Aromatic Solvent Vapors

“…18,19 Hierarchical nanostructures are advantageous because of their high specific surface areas, synergistic interactions and multiple functionalities, which are generally impossible to achieve using conventional materials. [20][21][22][23][24][25][26][27][28][29][30] For example, a hierarchical nanostructure based on three dimensional (3D) hollow carbon cubes with 1D carbon nanotube (CNT) on Sn exhibited excellent cyclical performance and rate capability for a prototype lithium-ion battery. 31 Despite these promising properties, construction of complex hierarchical functional materials over different length scales using functional molecules, in particular fullerene C60 or C70, remains a challenging task.…”

“…(a) Cyclic voltammograms (CV) of HFC at different scan rates(5, 10,20,50, 80, and 100 mV s -1 ), (b) corresponding calculated specific capacitance (Cs) vs. scan rates, (c) comparison of CV curves of HFC, FC and pristine C70 (scan rate 5 mV s -1 ), and (d) corresponding calculated specific capacitance. In panel (c) CD stands for current density.…”