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 .
Chirality is a desired property in functional semiconductors for optoelectronic, catalytic, and spintronic applications. Here, introducing enantiomerically‐pure 3‐aminobutyric acid (3‐ABA) into thin films of the 1D semiconductor dimethylammonium lead iodide (DMAPbI3) is found to result in strong circular dichroism (CD) in the optical absorption. X‐ray diffraction and grazing incidence small angle X‐ray scattering (GISAXS) are applied to gain molecular‐scale insights into the chirality transfer mechanism, which is attributed to a chiral surface modification of DMAPbI3 crystallites. This study demonstrates that the CD signal strength can be controlled by the amino‐acid content relative to the crystallite surface area. The CD intensity is tuned by the composition of the precursor solution and the spin‐coating time, thereby achieving anisotropy factors (gabs) as high as 1.75 × 10–2. Grazing incidence wide angle scattering reveals strong preferential ordering that can be suppressed via tailored synthesis conditions. Different contributions to the chiroptical properties are resolved by a detailed analysis of the CD signal utilizing an approach based on the Mueller matrix model. This report of a novel class of chiral hybrid semiconductors with precise control over their optical activity presents a promising approach for the design of circularly polarized light detectors and emitters.
A cellulose nanofibril-based hybrid gel material was
developed
by grafting the polymerized stearyl acrylate (PSA) and upconversion
nanoparticles (UCNPs) onto cellulose nanofibrils (CNFs) via Cu0-mediated radical polymerization (SET-LRP) to create a highly
cross-linked CNF system. A two-step strategy was exploited to surface-exchange
the ligand of the UCNPs from a hydrophobic ligand (oleic acid) to
a hydrophilic small-molecule ligand (2-acrylamido-2-methyl-1-propanesulfonic
acid, AMPS) and therefore be suitable for SET-LRP. The characteristics
and properties of the hybrid material (UCNP-PSA-CNF) were monitored
by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric
analysis (TGA), rheology, X-ray diffraction (XRD), and microscopic
analysis. Those characterization techniques prove the efficient modification
of the CNF, with the presence of 1.8% UCNPs. The luminescence measurement
was carried out using a homebuilt confocal microscope with a 980 nm
laser source. The nanostructure of UCNPs and their incorporated CNF
species were measured by small-angle X-ray scattering (SAXS). In addition,
this CNF-based hybrid gel has decisive rheological properties, such
as good viscoelasticity (loss tangent was below 0.35 for the UCNP-PSA-CNF
gel, while the PSA-CNF gel reached the highest value of 0.42), shear-thinning
behavior, and shape retention, and was successfully applied to three-dimensional
(3D) gel printing throughout various 3D print models.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.