Hierarchical Branched Mesoporous TiO₂–SnO₂ Nanocomposites with Well‐Defined n–n Heterojunctions for Highly Efficient Ethanol Sensing

Abstract

The direct assembly of functional nanoparticles into a highly crystalline mesoporous semiconductor with oriented configurations is challenging but of significance. Herein, an evaporation induced oriented co‐assembly strategy is reported to incorporate SnO2 nanocrystals (NCs) into a 3D branched mesoporous TiO2 framework by using poly(ethylene oxide)‐block‐polystyrene (PEO‐b‐PS) as the template, SnO2 NCs as the direct tin source, and titanium butoxide (TBOT) as the titania precursor. Owing to the combined properties of ultrasmall particle size (3–5 nm), excellent dispersibility and presence of abundant hydroxyl groups, SnO2 NCs can easily interact with PEO block of the template through hydrogen bonding and co‐assemble with hydrolyzed TBOT to form a novel hierarchical branched mesoporous structure (SHMT). After calcination, the obtained composites exhibit a unique 3D flower‐like structure, which consists of numerous mesoporous rutile TiO2 branches with uniform cylindrical mesopores (≈9 nm). More importantly, the SnO2 NCs are homogeneously distributed in the mesoporous TiO2 matrix, forming numerous n–n heterojunctions. Due to the unique textual structures, the SHMT‐based gas sensors show excellent gas sensing performance with fast response/recovery dynamics, high sensitivity, and selectivity toward ethanol.

Rational Design of Semiconductor‐Based Chemiresistors and their Libraries for Next‐Generation Artificial Olfaction

“…Accordingly, most p-type oxide semiconductors are excellent catalysts for oxidizing various reducing gases with low reactivity. It should be noted that n-type oxide semiconductors are usually used to detect highly reactive gases such as C 2 H 5 OH, [67,68] acetone, [69] HCHO, [70] CO, [71][72][73] H 2 , [74] and NO 2 [75][76][77][78] but generally ; c,d) gas sensing mechanisms of n-type and p-type oxide semiconductor gas sensors; e) the amount of oxygen chemisorption for n-type and p-type oxide semiconductor gas sensors. f) The gas responses of n-type and p-type oxide semiconductor gas sensors as a function of particle diameter and the enhancement gas response for p-type oxide semiconductor gas sensors via electronic/chemical sensitization and the decrease of particle size.…”

Inorganic-Diverse Nanostructured Materials for Volatile Organic Compound Sensing

“…Nanomaterials with porosity plays a vital role in the sensing studies of volatile alcoholic compounds. Porous structures of Ag-functionalized ZnO, Al-doped ZnO, Au loaded WO 3 , 3D-ordered In-doped ZnO, Si@ZnO NPs, Ag loaded graphitic C 3 N 4 , hierarchical mixed Pd/SnO 2 , SnO 2 fibers, hierarchical branched TiO 2 -SnO 2 , and hierarchical Co-doped ZnO were reported for their alcohol sensing utilities [ 212 , 213 , 214 , 215 , 216 , 217 , 218 , 219 , 220 , 221 ]. These porous nanostructures were synthesized by combustion method, nanocasting method, template mediated synthesis, microemulsion method, microdispensing method, solvothermal method, and calcination tactics.…”

Recent Advances of SnO2-Based Sensors for Detecting Volatile Organic Compounds

“…The uniform distribution of SnO 2 NCs in the pore walls of TiO 2 forms numerous n-n heterojunctions which are extremely useful for surface catalytic reaction. Owing to the rational combination of a hierarchical mesoporous structure, a high crystallinity, and well-defined n-n heterojunctions, the SHMT-based gas sensor shows an excellent sensing performance with a fast response and recovery dynamics, ultralow limit of detection and a superior selectivity (Zhao et al, 2019a). The cactus-like WO 3 -SnO 2 nanocomposite was prepared by one-step hydrothermal method by attaching many tiny SnO 2 nanospheres to large WO 3 nanospheres, which provided many active sites for the acetone molecule and provided heterojunctions between WO 3 and SnO 2 .…”