Silicon nanostructure-doped polymer/nematic liquid crystal composites for low voltage-driven smart windows

In this work, two silicon nanostructures were doped into polymer/nematic liquid crystal composites to regulate the electric-optical performance. Commercial SiO2 nanoparticles and synthesized thiol polyhedral oligomeric silsesquioxane (POSS-SH) were chosen as the dopants to afford the silicon nanostructures. SiO2 nanoparticles were physically dispersed in the composites and the nanostructure from POSS-SH was implanted into the polymer matrix of the composites via photoinduced thiol-ene crosslinking. SEM results indicated that the implantation of POSS microstructure into the polymer matrix was conducive to obtaining the uniform porous polymer microstructures in the composites while the introduction of SiO2 nanoparticles led to the loose and heterogeneous polymer morphologies. The electric-optical performance test results also demonstrated that the electric-optical performance regulation effect of POSS microstructure was more obvious than that of SiO2 nanoparticles. The driving voltage was reduced by almost 80% if the concentration of POSS-SH in the composite was nearly 8 wt% and the sample could be completely driven by the electric field whose voltage was lower than the safe voltage for continuous contact (24 V). This work could provide a creative approach for the regulation of electric-optical performance for polymer/nematic liquid crystal composites and the fabrication of low voltage-driven PDLC films for smart windows.

Research progress of carbon-assisted etching of silicon nanostructures

Silicon nanostructures are attracting growing attention due to their properties and promising application prospects in solar energy conversion and storage devices, thermoelectric devices, lithium-ion batteries, and biosensing technologies. The large-scale and low-cost preparation of silicon nanostructures is critical for silicon-based advanced functional devices commercialization. In this paper, the feasibility and mechanism of silicon nanostructure fabricated by non-metallic carbon catalytic etching, as well as the currently existing problems and future development trend are reviewed.

Research progress of silicon nanostructures prepared by electrochemical etching based on galvanic cells

Metal-assisted etching of silicon in HF aqueous solution has attracted widespread attention due to its potential applications in electronics, photonics, renewable energy, and biotechnology. In this paper, the basic process and mechanism of metal assisted electrochemical etching of silicon in vapor or liquid atmosphere based on galvanic cells are reviewed. This paper focuses on the use of gas-phase oxidants O2 and H2O2 instead of liquid phase oxidants Fe(NO3)3 and H2O2 to catalyze the etching of silicon in the vapor atmosphere of HF aqueous solution. The mechanism of substrate enhanced metal-assisted chemical etching for the preparation of large-area silicon micro nanostructure arrays is summarized, and the impact of substrate type and surface area on reactive etching is discussed.

Conversion of Amorphous Carbon on Silicon Nanostructures into Similar Shaped Semi-Crystalline Graphene Sheets

Graphene sheets displaying partial crystallinity and nanowire structures were formed on a silicon substrate with silicon nanowires by utilizing an amorphous carbon source. The carbon source was deposited onto the silicon nanostructured substrate by breaking down a polymer precursor and was crystallized by a nickel catalyst during relatively low temperature inert gas annealing. The resulting free-standing graphene-based material can remain on the substrate surface after catalyst removal or can be removed as a separate film. The film is flexible, continuous, and closely mimics the silicon nanostructure. This follows research on similar solid carbon precursor derived semi-crystalline graphene synthesis procedures and applies it to complex silicon nanostructures. This work examined the progression of the carbon, finding that it migrates through the thin film catalyst and forms the graphene only on the other side, and that the process can successfully be used to form 3D shaped graphene films. Semi-crystalline graphene has the possible application of being flexible transparent electrodes, and the 3D shaping opens the possibility of more complex configurations and applications.