A Porous Nanostructured ZnO Layer for Ultraviolet Sensing with Quartz Crystal Microbalance Technique

Porous films of metals and metal oxides have gained growing attention as potential materials for use in applications that require large, specific surface areas, such as sensors, supercapacitors, and batteries. In this study, a "black-metal"-like porous Zn-ZnO composite layer was grown by room temperature co-sputtering of Zn metal and ZnO:Ga (3 at/%) ceramic targets. Following deposition, a porous ZnO layer was obtained by a subsequent thermal annealing process at 400 °C in air. The morphology and structural properties of the obtained porous layered objects were analyzed. The porosity and chemical characteristics of the nanostructured ZnO layer obtained with the method herein described make it suitable to be used as a sensitivity-enhancing active layered element in quartz crystal microbalance (QCM)-based ultraviolet (UV) sensors. The prepared resonant ZnO/QCM sensors under UV radiation exhibited maximum shift up to 35 Hz for several "on-off" UV cycles, excellent response, and recovery times of 11 and 12 s, respectively.

Multifunctional Superwettable Material with Smart pH Responsiveness for Efficient and Controllable Oil/Water Separation and Emulsified Wastewater Purification

Developing multifunctional superwettable materials is highly demanded in the oil/water separation field but remains challenging due to the critical limitations of complex fabrication strategy and high cost. Herein, based on the cost-effective kaolin nanoparticles, we present a convenient and mild strategy for fabricating a smart superwettable material with multiple excellent performances, such as pH-responsive water wettability, self-cleaning property, favorable buoyancy, and air purification performance. By virtue of the dual rough surface structure and special chemical composition, the resultant material surface exhibits a superior pH-dependent wettability, which can be reversibly switched between superamphiphobicity and superhydrophilicity-superoleophobicity for many times in accordance with the pH value of the corresponding aqueous solution. As a result, the obtained superwettable material with reversible and controllable water wettability can be applied in efficient and continuous separation of multiple types of oil/water mixtures, especially the highly emulsified oil/water emulsions, via in situ or ex situ wettability change. To our knowledge, the smart material with the wetting property of superamphiphobicity that can be used for continuous emulsified wastewater purification has been rarely discussed in the emerging research works. In addition, the as-prepared material presents universal applicability to diversiform substrates and exhibits robust durability and stability against high-concentration salt solutions and rigorous mechanical abrasion. All of these above-mentioned advantages indicate that the as-prepared superwettable material will hold great potential in various practical applications, including oily wastewater remediation, smart aquatic device fabrication, liquid droplet manipulation, guiding liquid movement, and optimizing multiple operations in industrial fields.

Separation Mechanism and Construction of Surfaces with Special Wettability for Oil/Water Separation

Oil leakage and the discharge of oil/water mixtures by domestic and industrial consumers have caused not only severe environmental pollution and a threat to all species in the ecosystem but also a huge waste of precious resources. Therefore, the separation of oil/water mixtures, especially stable emulsion, has become an urgent global issue. Recently, materials containing a special wettability feature for oil and water have drawn immense attention because of their potential applications for oil/water separation application. In this paper, we systematically summarize the fundamental theories, separation mechanism, design strategies, and recent developments in materials with special wettability for separating stratified and emulsified oil/water mixtures. The related wetting theories that unveil the physical underlying mechanism of the oil/water separation mechanism are proposed, and the practical design criteria for oil/water separation materials are provided. Guided by the fundamental design criteria, various porous materials with special wettability characteristics, including those which are superhydrophilic/underwater superoleophobic, superhydrophobic/superoleophilic, and superhydrophilic/in-air superoleophobic, are systemically analyzed. These superwetting materials are widely employed to separate oil/water mixtures: from stratified oil/water to emulsified ones. In addition, the materials that implement the demulsification of emulsified oil/water mixtures via the ingenious design of the multiscale surface morphology and construction of special wettability are also discussed. In each section, we introduce the design ideas, base materials, preparation methods, and representative works in detail. Finally, the conclusions and challenges for the oil/water separation research field are discussed in depth.

Recent Progress in Fabrication and Applications of Superhydrophobic Coating on Cellulose-Based Substrates

Multifuntional fabrics with special wettability have attracted a lot of interest in both fundamental research and industry applications over the last two decades. In this review, recent progress of various kinds of approaches and strategies to construct super-antiwetting coating on cellulose-based substrates (fabrics and paper) has been discussed in detail. We focus on the significant applications related to artificial superhydrophobic fabrics with special wettability and controllable adhesion, e.g., oil-water separation, self-cleaning, asymmetric/anisotropic wetting for microfluidic manipulation, air/liquid directional gating, and micro-template for patterning. In addition to the anti-wetting properties and promising applications, particular attention is paid to coating durability and other incorporated functionalities, e.g., air permeability, UV-shielding, photocatalytic self-cleaning, self-healing and patterned antiwetting properties. Finally, the existing difficulties and future prospects of this traditional and developing field are briefly proposed and discussed.

Preparation of superhydrophobic coating with excellent abrasion resistance and durability using nanofibrillated cellulose

Nanofibrillated cellulose (NFC) is a renewable and environmentally friendly material.

Biomimetic super-lyophobic and super-lyophilic materials applied for oil/water separation: a new strategy beyond nature

Investigations in the field of oil/water separation materials with special wettability may accelerate the settlement of industrial oily wastewater and ocean oil spill accidents.