We have used a combination of X-ray and electron energy-loss spectroscopies along with DFT calculations to investigate the electronic structure of PTI/LiCl, a graphitic carbon nitride-type material with LiCl intercalation shown to photocatalyze the water-splitting reaction. The material is shown to have a band gap that is tunable with LiCl loading, with a minimum gap of 2.2 eV when fully loaded. This suggests that PTI/LiCl may be further optimized through control of their LiCl loading and shows that graphitic carbon nitride-type materials can be chemically tuned to improve their photocatalytic activity.

Adenovirus type 5 (Ad) is an efficient gene vector with high gene transduction potential, but its efficiency depends on its native cell receptors coxsackie- and adenovirus receptor (CAR) for cell attachment and α(v)β(3/5) integrins for internalization. To enable transduction of CAR negative cancer cell lines, we have coated the negatively charged Ad by noncovalent charge interaction with cationic PAMAM (polyamidoamine) dendrimers. The specificity for tumor cell infection was increased by targeting the coated Ad to the epidermal growth factor receptor using the peptide ligand GE11, which was coupled to the PAMAM dendrimer via a 2 kDa PEG spacer. Particles were examined by measuring surface charge and size, the degree of coating was determined by transmission electron microscopy. The net positive charge of PAMAM coated Ad enhanced cellular binding and uptake leading to increased transduction efficiency, especially in low to medium CAR expressing cancer cell lines using enhanced green fluorescent protein or luciferase as transgene. While PAMAM coated Ad allowed for efficient internalization, coating with linear polyethylenimine induced excessive particle aggregation, elevated cellular toxicity and lowered transduction efficiency. PAMAM coating of Ad enabled successful transduction of cells in vitro even in the presence of neutralizing antibodies. Taken together, this study clearly proves noncovalent, charge-based coating of Ad vectors with ligand-equipped dendrimers as a viable strategy for efficient transduction of cells otherwise refractory to Ad infection.

The transfer of supramolecular templating to the realm of metal-organic frameworks opens up new avenues to the design of novel hierarchically structured materials. We demonstrate the first synthesis of mesostructured zinc imidazolates in the presence of the cationic surfactant cetyltrimethylammonium bromide (CTAB), which acts as a template giving rise to ordered lamellar hybrid materials. A high degree of order spanning the atomic and mesoscale was ascertained by powder X-ray diffraction, electron diffraction, as well as solid-state NMR and IR spectroscopy. The metrics of the unit cells obtained for the zinc methylimidazolate and imidazolate species are a=(11.43±0.45), b=(9.55±0.35), c=(27.19±0.34) Å, and a=(10.98±0.90), b=(8.95±0.95), c=(26.33±0.34) Å, respectively, assuming orthorhombic symmetry. The derived structure model is consistent with a mesolamellar structure composed of bromine-terminated zinc (methyl)imidazolate chains interleaved with motionally rigid cationic surfactant molecules in an all-trans conformation. The hybrid materials exhibit unusually high thermal stability up to 300 °C, at which point CTAB is lost and evidence for a thermally induced transformation into poorly crystalline mesostructures with larger feature sizes is obtained. Treatment with ethanol effects the extraction of CTAB from the material, followed by facile transformation into pure microporous ZIF-8 nanoparticles within minutes, thus demonstrating a unique transition from a mesostructure into a microporous zinc imidazolate.

Rapid progress in the synthesis of nanostructures with tailor-made morphologies necessitates adequate analytical tools to unravel their physical properties. In our study, we investigate, on the nanometer scale, the band gap of individual [TBA x H1–x ]+[Ca2Nb3O10]− nanosheets obtained through intercalation–exfoliation of the layered bulk phase KCa2Nb3O10 with tetra-n-butyl­ammonium hydroxide (TBAOH) using valence electron energy loss spectroscopy (VEELS) in the scanning transmission electron microscope (STEM). The nanosheets consist of an anionically charged perovskite layer with cationic organic ligands surrounding it. Because of the hybrid nature, a careful acquisition and analysis protocol is required since the nanosheets disintegrate easily under electron beam irradiation. The VEELS data reveal a fundamental band gap of an individual freely suspended perovskite nanosheet to be 2.9 ± 0.2 eV and optically allowed transitions above 3.8 ± 0.2 eV (optical band gap). The spatial resolution of the measurements is about 9 nm, taking into account 50% of the excitations when illuminating with an incident electron beam of 1 nm diameter. Our investigations reveal that the band gap of an individual nanosheet is not changed significantly compared to the bulk phase, which is confirmed by UV–vis data. This is rationalized by the quasi-2D electronic structure of the bulk material being preserved upon delamination.