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Surface-enhanced Raman spectroscopy (SERS) of semiconducting TiO2 was used for studying binding modes and surface reactions of molecules bound at the interface but is generally limited by low signa...

International audience; Owing to their high and tunable porosity as well as great chemical diversity, metal–organic frameworks (MOFs) have shown great promise over the past 20 years for a wide range of applications, including gas storage/separation, catalysis, and biomedicine. To date, MOF nanoparticles (NPs) have mostly been obtained as polycrystalline powders or spherical nanocrystals while anisotropic MOFs nanocrystals have been less explored and are of interest in the fields of catalysis, sensing, and electronics. One of the main challenges for the practical application of MOFs is thus to control the crystal size, morphology, and multiscale porosity of these materials while developing adequate shaping strategies. In this review, we cover recent advances in the different synthetic strategies of one-dimensional (1D) MOF nanocrystals as well as hierarchical porous superstructures based on tubular MOFs. We describe the architectures based on MOFs nanotubes (NTs), nanowires (NWs), and nanorods (NRs). Our discussion is focused on the synthetic approaches that drive the structure, crystallinity, size, and morphology of these hierarchical porous hybrid materials. Finally, their potential for different applications is presented.

We report the selective formation of endoperoxides by aerobic TiO2 photocatalysis through the cyclic addition of dioxygen and a non-conjugated diene, the first heterogeneous catalytic system for endoperoxide synthesis. This green protocol does not require any additive and the photocatalyst is abundant and recyclable, providing a yield up to 64% and >20:1 diastereoselectivity. Mechanistic investigations were carried out by using product analysis, kinetic studies, O-18 labelling experiments, electron-spin resonance and a set of quenching experiments. Superoxide (but not singlet oxygen, triplet oxygen or peroxide) is directly involved in the reaction cascade to form the endoperoxide product. The new findings may be helpful for future for designing eco-friendly and energy sustainable strategies for selective oxygenation reactions using semiconductors, O2 and sunlight.

Because of the increasing prevalence of multidrug resistance feature, several investigations have been so far reported regarding the antibiotic alternative supramolecular bioactive agents made of hybrid assemblies. In this regard, it is well-established that combinational therapy inherited by assembled supramolecular structures can improve the bioactivity to some extent, but their mode of action has not been studied in detail. We provide first direct evidence that the improved mechanism of action of antimicrobial supra-amphiphilic nanocomposites differs largely from their parent antimicrobial peptide-based polymers. For the construction of a hybrid combinational system, we have synthesized side-chain peptide-based antimicrobial polymers via RAFT polymerization and exploited their cationic nature to decorate supra-amphiphilic nanocomposites via interaction with anionic polyoxometalates. Because of cooperative antimicrobial properties of both the polymer and polyoxometalate, the nanocomposites show an enhanced antimicrobial activity with a different antimicrobial mechanism. The cationic stimuli-responsive peptide-based polymers attack bacteria via membrane disruption mechanism, whereas free radical-mediated cell damage is the likely mechanism of polymer-polyoxometalate-based supra-amphiphilic nanocomposites. Thus, our study highlights the different antimicrobial mechanism of combinational systems in detail, which improves our understanding of enhanced antimicrobial efficacy.

Simultaneous CO2 reduction and water oxidation as a coupled process is an important challenge in the quest of clean energy production. Herein, we report a metal oxide based heterogeneous catalytic system, which not only couples CO2 reduction with water oxidation, but also provides very high turnover number for CO2 reduction with scalability. Such a catalytic system can simultaneously oxidize water and release the generated electrons for reduction of CO2 with a maximum turnover number and turnover frequency as high as 1.4 × 106 and 610 s−1, respectively, following effective catalyst concentration; whereas, turnover number and turnover frequency is 1366 and 1380 h−1 per mole of catalyst, respectively. The starting materials for this catalytic process are CO2 and water while the end products are oxygen and formic acid and in few cases, formaldehyde. The prospect of using the formic acid generated during our process in fuel cells to generate green energy is also worth mentioning.

In this study we have shown dislocations/defects can be introduced in the form of supramolecularly bound polyacrylic acid and urea based scaffold networks and metal oxide nanoparticles in concrete. By virtue of their supramolecular bonding sites, polyacrylic acid and urea create a network of struts. These struts act as dislocations in an otherwise uniform concrete structure which in turn increase the strength of the concrete. We have also shown that the length of these struts can also be controlled. Such a control over the strut length also led to influencing the strength of the concrete. In short we have shown that effective stress for unit matrix area can be reduced by introducing defects/dislocations in the form of struts which distribute the external applied stress. Consequently the higher the extent of dislocation, the larger is the capacity of the concrete matrix to withstand externally applied stress, the higher is its mechanical strength. We further added ZrO2 and TiO2 nanoparticles to the concrete matrix which enhance the thermal resistivity of the concrete.

A supramolecular poly-electrolyte complex (SPEC) comprising poly-electrolyte acrylic acid with supramolecularly complexed guanidium is reported. This complex shows pH responsive phase transitions, which are described and characterized using microscopy, spectroscopy, density functional theory studies and Monte Carlo simulations. The phase behaviour of the SPEC is exploited by loading a dye like perylene and a drug, viz., doxorubicin, and their pH dependent controlled release is demonstrated, owing to the pH dependent phase change of the SPEC.

DOI: 10.1021/acs.inorgchem.5b02570 URL: http://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.5b02570 Filiació URV: SI The formation pathway of a closed spherical cluster [Mo132], starting from a library of building blocks of molybdate anions, has been reported. Electrospray ionization mass spectrometry, Raman spectroscopy, and theoretical studies describe the formation of such a complex cluster from a reduced and acidified aqueous solution of molybdate. Understanding the emergence of such an enormous spherical model cluster may lead to the design of new clusters in the future. Formation of such a highly symmetric cluster is principally controlled by charge balance and the emergence of more symmetric structures at the expense of less symmetric ones.

An inexpensive, facile, and environmentally benign method has been developed for the preparation of stimuli-responsive and self-healing polyacrylic acid–chitosan-based supramolecular hydrogels. Guanidine hydrochloride is used as the supramolecular crosslinker to form an interconnected network with polyacrylic acid–chitosan complex. Because of the dynamic equilibrium between the hydrogen-bonding sites of the components, the hydrogels were found to be self-healable and sensitive to biochemical-stimulus, such as pH. Controlled loading of drug like doxorubicin and its significant anticancer activity of such hydrogels is worth mentioning.