Biopolymer‐Templated Deposition of Ordered and Polymorph Titanium Dioxide Thin Films for Improved Surface‐Enhanced Raman Scattering Sensitivity

Abstract

Titanium dioxide (TiO 2 ) is an excellent candidate material for semiconductor metal oxide-based substrates for surface-enhanced Raman scattering (SERS). Biotemplated fabrication of TiO 2 thin films with a 3D network is a promising route for effectively transferring the morphology and ordering of the template into the TiO 2 layer. The control over the crystallinity of TiO 2 remains a challenge due to the low thermal stability of biopolymers. Here is reported a novel strategy of the cellulose nanofibril (CNF)-directed assembly of TiO 2 /CNF thin films with tailored morphology and crystallinity as SERS substrates. Polymorphous TiO 2 /CNF thin films with well-defined morphology are obtained by combining atomic layer deposition and thermal annealing. A high enhancement factor of 1.79 × 10 6 in terms of semiconductor metal oxide nanomaterial (SMON)-based SERS substrates is obtained from the annealed TiO 2 /CNF thin films with a TiO 2 layer thickness of 10 nm fabricated on indium tin oxide (ITO), when probed by 4-mercaptobenzoic acid molecules. Common SERS probes down to 10 nm can be detected on these TiO 2 /CNF substrates, indicating superior sensitivity of TiO 2 /CNF thin films among SMON SERS substrates. This improvement in SERS sensitivity is realized through a cooperative modulation of the template morphology of the CNF network and the crystalline state of TiO 2 .

Cellulose‐Reinforced Programmable and Stretch‐Healable Actuators for Smart Packaging

“…CNFs are one kind of humidity‐sensitive and 1D biopolymer with high stiffness and are widely used as a nano‐reinforcement phase to enhance the mechanical property [ 48 ] or ordering [ 49 ] of nanocomposites. Showing strong interfacial interactions with CNF through physical entanglements and hydrogen bonding, PVA was incorporated to increase the compliance of the cellulose‐reinforced actuator.…”

State of the art of ultra-thin gold layers: formation fundamentals and applications

“…Au/titanium (TiO 2 ) hybrid nanomaterials have been applied in many elds, including plasmonic sensors, photocatalysis, and as advanced electron transport layers for solar cells. [91][92][93][94][95] Based on advanced nanotechnology, TiO 2 matrixes can be developed into various nanostructures for pursing an enhanced performance of the nal devices. Therefore, regarding the preparation of Au/TiO 2 hybrid nanomaterials by sputter deposition or evaporation strategies, it can be expected that the nanostructures of TiO 2 matrixes or substrates could affect the growth behavior of Au during the deposition process.…”

Template-Induced Growth of Sputter-Deposited Gold Nanoparticles on Ordered Porous TiO2 Thin Films for Surface-Enhanced Raman Scattering Sensors

“…Gold/titanium dioxide (Au/TiO 2 ) hybrid nanomaterials are promising in many applications that rely on localized surface plasmon resonances (LSPRs) and surface-enhanced Raman scattering (SERS). These applications include sensors, photocatalysis due to the enhanced photochemical activity, advanced electron transport layers for solar cells, and electrodes for batteries due to high conductivity. − Especially, porous Au/TiO 2 hybrid nanomaterials with ordered or periodic structures have attracted much attention recently, since the porous structure increases the accessibility of target molecules and acts as an active part in semiconductor metal oxide nanomaterial (SMON) based sensors. − In general, Au nanoparticles and nanostructures exhibit a strong, size-dependent LSPR effect. The wavelength and intensity of the plasmon resonance absorption bands are highly related to the size and corresponding size distribution, as well as the shape of the Au nanoparticles and nanostructures. − For instance, Dinh et al prepared three-dimensional (3D) ordered thin-shell Au/TiO 2 hollow nanospheres as visible-light-driven photocatalysts .…”