Enhanced electro-optic characteristics of polymer-dispersed nano-sized liquid crystal droplets utilizing PEDOT:PSS polymer composite

Reverse-Mode Polymer-Stabilized Liquid Crystal Films with Enhanced Peel Strength and Electro-Optical Performance Based on Photoreactive Self-Assembly Alignment Layers and Patterned Polymer Walls

Polymer-stabilized liquid crystal (PSLC) is a promising material toward the practical application of serving as energy-saving reverse-mode smart windows owing to its superior electro-optical (E-O) properties, simple and efficient processability, and compatibility to most practical circumstances. However, its feeble peel strength originated from low polymer content and poor adhesion between polymer networks and substrates inhibited its large-scale flexible film production. It is still a challenging task to derive good mechanical properties and superior E-O performance for PSLCs at the same time. In this study, a highly durable liquid crystal/polymer composite film showing enhanced peel strength and excellent E-O properties was attained by simultaneously building photoreactive self-assemble alignment layers through an efficient one-step method and the sculpture of a patterned polymer wall structure. This film has comprehensive ascendant E-O properties of lower driving voltages, faster response times, and higher contrast ratio, together with an over 30 times lift of the peel strength. The effectuation mechanisms of the alignment, E-O properties, peel-strength, microstructures, and cyclic durability of the films have been systematically studied. This novel liquid crystal/polymer composite film demonstrates advantages in every aspect of performance compared to traditional PSLC devices, which hoards promising applications in smart windows for cars and buildings.

High performance langasite based SAW NO2 gas sensor using 2D g-C3N4@TiO2 hybrid nanocomposite

Nitrogen dioxide (NO₂) gas has emerged as a severe air pollutant that causes damages to the environment, human life and global ecosystems etc. However, the currently available NO₂ gas sensors suffers from insufficient selectivity, sensitivity and long response times that impeding their practical applicability for room temperature (RT) gas sensing. Herein, we report a high performance langasite (LGS) based surface acoustic wave (SAW) RT NO₂ gas sensor using 2-dimensional (2D) g-C₃N₄@TiO₂ nanoplates (NP) with {001} facets hybrid nanocomposite as a chemical interface. The g-C₃N₄@TiO₂ NP/LGS SAW device showed a significant negative frequency shift (∆f) of ~19.8 kHz which is 2.4 fold higher than that of the pristine TiO₂ NP/LGS SAW sensor toward 100 ppm of NO₂ at RT. In addition, the hybrid SAW device fascinatingly exhibited a fast response/recovery time with a low detection limit, high selectivity, and an effective long term stability toward NO₂ gas. It also exhibited an enhanced and robust negative frequency shifts under various relative humidity conditions ranging from 20% to 80% for 100 ppm of NO₂ gas. The high performance of the g-C₃N₄ @TiO₂ NP/LGS SAW gas sensor can be attributed to the enhanced mass loading effect which was assisted by the large surface area, oxygen vacancies, OH and amine functional groups of the n-n hybrid heterojunction of g-C₃N₄@TiO₂ NP that provide abundant active sites for the adsorption and diffusion of NO₂ gas molecules. These results emphasize the significance of the integration of 2D materials with metal oxides for SAW based RT gas sensing technology holds great promise in environmental protection.

Photochromic TiO2/PEGDA organogels

Photochromic materials can be used for modulation of the visible and infrared light transmittance for providing privacy or energy saving by blocking the heat. Titanium dioxide (TiO₂) nanoparticles has been well reported as a promising photochromic material. However, a high photochromic response from TiO₂ can be observed only when the nanoparticles are dispersed in a strong photogenerated hole scavenger at a liquid state, but polymer composites are less responsive due to lack of hole scavenging capability. However, it is intricate to apply suspensions in real window devices because of possible leaking. Here, we describe the preparation of TiO₂ quantum dot (QD)-based gels from polyethylene glycol diacrylate (PEGDA), N,N-Dimethylformamide (DMF), and ethanol (EtOH). Photochromic gels with TiO₂ contents (1-5 volume%) show performance comparable to their colloidal counterparts with capable of photodarkening within 30 min with a transmittance change ranging from 35.8 to 84.5% at 550 nm. These gels were capable of fully recovering the initial transmittance when not exposed to ultraviolet (UV) light within 3-8 h. The photochromic gel systems with ethanol shows reasonable stability by decreasing in transmittance recovery only by less than 10% in 10 cycles. A potential application for the developed photochromic gels can be photochromic windows.