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Hydrogels of biopolymers are gradually substituting synthetic hydrogels in tissue engineering applications due to their properties. However, biopolymeric hydrogels are difficult to standardize because of the intrinsic variability of the material and the reversibility of physical crosslinking processes. In this work, we synthesized a photocrosslinkable derivative of chitosan (Cs), namely methacrylated chitosan (CsMA), in which the added methacrylic groups allow the formation of hydrogels through radical polymerization triggered by UV exposure. We then performed a systematic study to link the physical properties of the materials to its preparation parameters to standardize its preparation according to specific applications. We studied the properties of CsMA solutions and the derived hydrogels using a statistical method, namely, response surface method, which allowed us to build empirical models describing material properties in terms of several selected processing factors. In particular, we studied the viscosity of CsMA solutions as a function of CsMA concentration, temperature, and shear rate, while hydrogel compression modulus, morphology, degradation and solubilization were investigated as a function of CsMA concentration, photoinitiator concentration and UV exposure. CsMA solutions resulted in shear thinning and were thus suitable for extrusion-based 3D printing. The CsMA hydrogel was found to be highly tunable, with a stiffness in the 12–64 kPa range, and was stable over a long timeframe (up to 60 days). Finally, the possibility to engineer hydrogel stiffness through an empirical model allowed us to hypothesize a number of possible applications based on the mechanical properties of several biological tissues reported in the literature. [ABSTRACT FROM AUTHOR]

Redox active materials, whose optical emission and absorption spectra are both electrically switchable, are said to be dual functional electrochromic and electrofluorochromic materials. They are intriguing for a wide range of applications, e.g., displays, smart-windows, sensing, information storage, and encryption/anticounterfeiting devices. Herein, we investigated the performance of benzothiadiazole-arylamine compounds serving as either anodic components or electroactive fluorophores, in dual functional electrochromic/electrofluorochromic solid state devices, fabricated as all-in-one ITO/gel/ITO sandwiches. We systematically investigated the electrochromic and electrofluorochromic responses of the devices, by varying the anode among a set of structurally different benzothiadiazole-arylamines and using the ethyl viologen as a cathodic component. All the devices show an interesting vis-NIR electrochromism with a pink/orange to deep dark color switching, arising from the superposition of the electrochromic bands of the viologen and arylamine, with contrasts up to 36%/75% in the NIR/vis ranges and switching times from fractions of a second up to several seconds. Moreover, they show a panchromatic fluorescence from about 450 nm up to 850 nm, due to the intramolecular charge transfer character of the emission typical of these arylamine–benzothiadiazole-arylamine compounds with donor–acceptor–donor architecture. Notably, the relatively strong fluorescence of the devices (fluorescence quantum yields up to 38%) due to the aggregation induced emission (AIE) of the fluorophores in the gel (fluorescence enhancement of up to 63 times with respect to the solution phase with comparable polarity) undergoes a voltage-dependent quenching, with electrofluorochromic contrast ratios of up to 9, and a shift of the emission from NIR/red to yellow. Such an electrofluorochromic response is due to an uneven fluorescence quenching across the whole emission band, the twisted charge transfer states being majorly quenched at lower energy (red-NIR range). Interestingly, the voltage threshold for achieving the above electrochromic and electrofluorochromic responses increases with the first oxidation potential of the anodic component. Mechanistic insights provided by electrochemical impedance spectroscopy clearly show that the above threshold corresponds to the onset for electron injection/ejection at the cathode and anode, respectively, and depends on the difference between the viologen reduction potential and the oxidation potential of the arylamine. Finally, the devices show high stabilities with more than 2000 life cycles. [ABSTRACT FROM AUTHOR]

Electrochromism/electrofluorochromism is the reversible tuning of the absorption/photoluminescence by redox processes. Dual functional electrochromic/electrofluorochromic materials can be exploited in, for example, smart windows, encryption/anticounterfeiting technologies, displays, and biomedical sensors. While electrofluorochromic materials showing tunable fluorescence intensity are relatively widespread, those with tunable color emission are not. Moreover, electrofluorochromic materials with tunable emission in the near‐infrared (NIR) range are seldom encountered. Here, this work shows a new molecular approach to afford both the above functionalities, in addition to red–NIR electrochromism, by combining the properties of highly stable arylamine radical cation mixed valence species, with those of donor–acceptor systems exhibiting the photoinduced twisted intramolecular charge transfer mechanism. [ABSTRACT FROM AUTHOR]

A high-yield synthesis of pure anatase titania nanorods has been achieved through a nonaqueous microwave-based approach. The residual organics on nanoparticles surfaces were completely removed under ozone flow at room temperature in air. The TiO2 nanorods, with average lengths of 27.6 ± 5.8 nm and average diameters of 3.2 ± 0.4 nm, were characterized by powder X-Ray diffraction, transmission electron microscopy, selected area diffraction, BET surface area analysis and FT-IR spectroscopy. The photocatalytic performances of the as-synthesized TiO2 nanorods and platinum loaded TiO2 nanorods were implemented with respect to both commercial P25 and platinum loaded P25. Performance enhancements should be attributed to effects like differences in the adsorption capacity and in the separation efficiency of the photogenerated electrons-holes. [ABSTRACT FROM AUTHOR]

Homolog series based on three aromatic rings bearing terminal alkoxy chain of various lengths named 4-(4-(alkoxy)phenylimino)methyl)phenyl nicotinate (An) were synthesized. The alkoxy-chain length changed between 6, 8 and 16 carbons. Mesomorphic and optical properties were carried out via differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Elemental analyses, FT-IR and NMR spectroscopy were carried out to elucidate the molecular structures of the prepared derivatives. Mesomorphic results indicated that all the synthesized homologs (An) are monomorphic possessing the nematic (N) phase enantiotropically with wide thermal stability. Computational simulations were measured via density functional theory (DFT) theoretical calculation tool. The estimated thermal and geometrical parameters are in agreement with the experimental data. By discussing the estimated parameters, it was found that the molecular architecture, dipole moment and the polarizability of the investigated compounds are highly affected by the length of the attached terminal flexible chain and the location of the nitrogen atom in the other terminal aromatic ring. Binary phase diagrams of two corresponding homologs with different proportionating terminals were constructed, and their binary phase physical properties were discussed in terms of the temperature range and stability of the N phase. [ABSTRACT FROM AUTHOR]

Here we present a colloidal approach to synthesize bismuth chalcohalide nanocrystals (BiEX NCs, in which E=S, Se and X=Cl, Br, I). Our method yields orthorhombic elongated BiEX NCs, with BiSCl crystallizing in a previously unknown polymorph. The BiEX NCs display a composition-dependent band gap spanning the visible spectral range and absorption coefficients exceeding 10 5  cm -1 . The BiEX NCs show chemical stability at standard laboratory conditions and form colloidal inks in different solvents. These features enable the solution processing of the NCs into robust solid films yielding stable photoelectrochemical current densities under solar-simulated irradiation. Overall, our versatile synthetic protocol may prove valuable in accessing colloidal metal chalcohalide nanomaterials at large and contributes to establish metal chalcohalides as a promising complement to metal chalcogenides and halides for applied nanotechnology., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Ruling over the surface chemistry of metal halide perovskite nanocrystals (NCs) is crucial to access reliable luminophores. Here, we provide an atomic-level description of the surface of colloidal CsPbBr 3 NCs, achieving an effective passivation strategy that leads to near-unity photoluminescence quantum yield. To this end, we used two different types of CsPbBr 3 NCs, which had been synthesized with an outer shell of either oleylammonium bromide ion pairs or Cs-oleate complexes. We perturbed the dynamic equilibria at the NCs' surface with ligands from a comprehensive library, including amines (and their conjugated acids) with different basicities, chain lengths, and steric encumbrances. We demonstrate that control of both ligand binding affinity and ligand-to-NC molar ratio is essential to attain thermodynamically stable coordination of the NC surface. We thus present a reliable protocol for managing the surface chemistry of colloidal CsPbBr 3 NCs and for selectively addressing their ligand-induced morphological (and structural) transformations.