Research

Sculptured Nano Forests (SNAFs)

Glancing angle deposition (GLAD), custom-built physical vapor deposition (PVD) operated at an incident angle > 80o with respect to the substrate normal, is employed to fabricate a close-packed array composed of separated nanopillars due to the self-shadowing effect and temperature-limited adatom diffusion. The deposited nanopillars exhibit sculpturableshapes through controlling substrate movement, and are made of a wide range of materials (including ls, semiconductors and dielectrics). Such nanopillar arrays are called sculptured nanoforests (SNAFs).

Metallic nanohelices

Metallic nanohelicestypically have a helical pitch > 100 nm, and exhibit intrinsic linear and nonlinear optical activity in the UV-visible-near IR region that can be tuned by engineering materials and helicity.

Chiral Nanoparticles (CNPs)

Fast-substrate-rotation GLAD (FSR-GLAD) is operated to generate llic CNPs having a nominal helical pitch < 10 nm, although they appear to be achiral nanoparticles. Clockwise and counterclockwise substrate rotations lead to right-handed and left-handed CNPs, respectively. The sub-10 nm-pitch CNPs exhibit chiral helicity comparable to the enantiomeric size, to substantially enhance the enantioselective interaction of enantiomers and CNPs. CNPs are made of unary ls and high-entropy alloys. It is highly desired to develop prominent chirality-related applications, such as refractive index sensing, enantiodifferentiationand heterogeneous asymmetric catalysis.

Optoelectronic Devices

Semiconductor nanopillar arrays (NaPAs) can reduce light reflection loss, suppress recombination dynamics, guide charge transport, and relax stress and strain in flexible optoelectronic devices, to improve optoelectronic performance and stability under mechanical bending. Semiconductor NaPAscan function as charge carrier (electron and hole) transporting layers hybridized with photovoltaically active materials (such as perovskite), to fabricate optoelectronic (flexible) devices with high and stable optoelectronic performance.  

Inorganic Sculptured Extracelluar Nanomatrices (iSECnMs)

SNAFs made of biocompatible materials (such as silica) function as iSECnMs, to swiftly induce differentiation of neural stem cells (NSCs) to specific cell lineages. Diverse nanostructure-determined physical cues, such as matrix stiffness and topography, contribute to activating significant bio-signaling pathways of NSCs lying on the iSECnMs. Hence, engineering physical cues of iSECnMsleads to control the differentiated cell lineages. Furthermore, not applying traditional chemical growth factors result in minimizing the risk of carcinogenicity and tumorigenesis in vivoafter cell transplantation, paving the way for developing cell therapies to ultimately treat neurodegenerative diseases with no adverse effect.

Metal-assisted Chemical etching (MACE)

MACE is a low-cost, simple-process wet chemical etching of silicon wafers to produce silicon nanowires (SiNWs). Typically, Ag are galvanically reduced to nucleate at a Si surface owing to the oxidation of Si, and then sink (scratch)  into the bulk silicon, leaving the residues as SiNWs.

  • Fabrication of
    solid SiNWs without pores by etching lightly doped wafers;
  • Fabrication
    of mesoporous SiNWs by etching heavily doped wafers;
  • As-generated SiNWs inherit
    the intrinsic semiconductor properties (dopant element and doping lever)
    of their mother wafers.