The hydrothermal synthesis of SrTiO3 in a Sr­(OH)2/NaOH solution by reaction of four different single crystalline titanium precursors (anatase, rutile, sodium titanate, and hydrogen titanate) having the same nanowire morphology was investigated under stagnant fluid conditions. Owing to the low solubility and dissolution rate of the parent phases, the reaction mainly occurs in a thin interfacial fluid layer. The new phase only grows on the substrate surface, and the morphology evolution is largely controlled by the interface through the coupling of substrate dissolution and SrTiO3 crystallization. The pseudomorphic replacement of the precursor by the product occurs if complete surface coverage is attained. Depending on the crystallographic matching, the parent crystal can either transform in a mesocrystal as happens with anatase via a topochemical transformation or in a polycrystalline product as observed with sodium titanate. In contrast, if the product grows in the form of isolated particles or with dendritic morphology, as in the case of hydrogen titanate and, to a lesser extent rutile, the new compound will not inherit the precursor morphology. When well-defined interfaces are missing, as happens when amorphous titanium hydroxide gel suspensions are used as precursors, the crystallization of SrTiO3 occurs by a completely different pathway, i.e., oriented self-assembly of nanocrystals in mesocrystals.

The mechanisms driving the mutual crystallographic alignment of nanocrystals in mesocrystals are various and not yet fully understood. As discussed in this paper, formation of mesocrystals can result from a topochemical reaction between single crystal particles or templates suspended in a liquid phase and ionic/molecular species in solution. In such a case, the initial particle morphology is retained in the final mesocrystal. If the transformation is not topotactic, the final product will maintain no memory of the precursor morphology. The magnitude of the lattice mismatch as well as the defective state of the precursor surface probably determine the degree of mutual crystallographic alignment of the nanocrystals which nucleate and grow on the substrate. Although identified by studying the hydrothermal crystallization of SrTiO3 from different single crystal titania precursors, this mechanism is very general and applicable to a variety of compounds and experimental situations, including solvothermal and molten salt syntheses.

Mechanistic insights from operando Raman spectroelectrochemistry establishes that synergistic support–catalyst interactions is vital for rational design of electrocatalytic systems to achieve efficient hydrogen generation in alkaline medium.

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Two new polyoxometalate (POM)-based hybrid monomers (Bu4 N)5 (H)[P2 V3 W15 O59 {(OCH2 )3 CNHCO(CH3 )CCH2 }] (2) and (S(CH3 )2 C6 H4 OCOC(CH3 )=CH2 )6 [PV  2Mo10 O40 ] (5) were developed by grafting polymerizable organic units covalently or electrostatically onto Wells-Dawson and Keggin-type clusters and were characterized by analytical and spectroscopic techniques including ESI-MS and/or single-crystal X-ray diffraction analyses. Radical initiated polymerization of 2 and 5 with organic monomers (methacryloyloxy)phenyldimethylsulfonium triflate (MAPDST) and/or methylmethacrylate (MMA) yielded a new series of POM/polymer hybrids that were characterized by (1) H, (31) P NMR and IR spectroscopic techniques, gel-permeation chromatography as well as thermal analyses. Preliminary tests were conducted on these POM/polymer hybrids to evaluate their properties as photoresists using electron beam (E-beam)/extreme ultraviolet (EUV) lithographic techniques. It was observed that the POM/polymer hybrid of 2 with MAPDST exhibited improved sensitivity under EUV lithographic conditions in comparison to the MAPDST homopolymer resist possibly due to the efficient photon harvesting by the POM clusters from the EUV source.

Stabilization of the electroactive redox centers on ideally polarisable conductive electrodes is a critical challenge for realizing stable, high performing pseudocapacitive energy storage devices. Here, we report a top-down, electrochemical nanostructuring route based on voltammetric cycling to stabilize β-MnO on a single walled carbon nanotube (CNT) scaffold from a MnMoO precursor. Such in situ nanostructuring results in controlled disintegration of an ∼8 μm almond like structure to form ∼29 nm β-MnO resulting in a 59% increase in the specific surface area and a 31% increase in the porosity of the pseudocapacitive electrode. Consequently, the specific capacitance and areal capacitance increase by ∼75% and ∼40%, respectively. Such controlled, top-down nanostructuring is confirmed through binding energy changes to Mo 3d, C 1s, O 1s and Mn 2p respectively in XPS. Furthermore, Raman spectral mapping confirms the sequential nanostructuring initiating from the interface of CNTs with MnMoO and proceeding outwards. Thus, the process yields the final CNT/β-MnO electrode that is electrically conductive, facilitates rapid charge transfer, and has increased capacitance and longer stability. Furthermore, the charge-transfer resistance and equivalent resistance are significantly lower compared to conventional activated carbon based electrodes.

Anthropogenically triggered escalating contamination of water by heavy-metal ions (As 3+ , Cr 6+ , Cd 2+ , and Hg 2+ ) demands newer and efficient types of adsorbents for their comprehensive scavenging. The wide pH range (pH 2−13) at which such contamination persists makes it challenging to realize a single-step remediation approach. Addressing these escalating demands, a singular adsorbent capable of capturing multiple heavy metal ions with high adsorption capacity across a wide range of pH is herewith reported for sustainable water remediation. Threedimensional dendritic mesoporous nanostructured carbon florets (NCFs) with high specific surface area (936 m 2 /g) and easily accessible open-ended pore structure (1.23 cm 3 /g) achieve highly efficient removal of multiple heavy metal ions (As 3+ , Cr 6+ , Cd 2+ , and Hg 2+ ). The hydrophilic surface of NCF ensures extensive and efficient interfacing with the water feedstock, while its chemical stability ensures its effectiveness as an adsorbent over a wide pH range (pH 2 to pH 13). The synergistic combination of these factors enables excellent adsorption efficiency (AE; ranging from 80% to 90%) and uniformly high adsorption capacity (q e ) toward a variety of heavy-metal ions such as Hg 2+ (395 ± 4 mg/g), Cd 2+ (402 ± 5 mg/ g), Cr 6+ (436 ± 3 mg/g), and As 3+ (412 ± 4 mg/g). Moreover, the gravity-driven purification of water does not demand any external source of electrical power and is scalable for on-site implementation. Facile regeneration of the NCF and its reusability over multiple cycles is also demonstrated for practical and sustainable application in water remediation.

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