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Monodisperse and semi-faceted ultra-small templated mesoporous silica nanoparticles (US-MSNs) of 20–25 nm were synthesized using short-time hydrolysis of tetraethoxysilane (TEOS) at room temperature, followed by a dilution for nucleation quenching. According to dynamic light scattering (DLS), a two-step pH adjustment was necessary for growth termination and colloidal stabilization. The pore size was controlled by cetyltrimethylammonium bromide (CTAB), and a tiny amount of neutral surfactant F127 was added to minimize the coalescence between US-MSNs and to favor the transition towards internal ordering. Flocculation eventually occurred, allowing us to harvest a powder by centrifugation (~60% silica yield after one month). Scanning transmission electron microscopy (STEM) and 3D high-resolution transmission electron microscopy (3D HR-TEM) images revealed that the US-MSNs are partially ordered. The 2D FT transform images provide evidence for the coexistence of four-, five-, and sixfold patterns characterizing an "on-the-edge" crystallization step between amorphous raspberry and hexagonal pore array morphologies, typical of a protocrystalline state. Calcination preserved this state and yielded a powder characterized by packing, developing a hierarchical porosity centered at 3.9 ± 0.2 (internal pores) and 68 ± 7 nm (packing voids) of high potential for support for separation and catalysis. [ABSTRACT FROM AUTHOR]

Methylene blue (MB) is a well-established and extensively studied photosensitizer for photodynamic therapy (PDT), since it can generate singlet oxygen with a high quantum yield upon irradiation within the phototherapeutic (600–950 nm) window. However, its activity can decrease due to the formation of dimers or higher aggregates, which can take place in an aqueous solution at relatively high concentrations. The incorporation of this molecule into a matrix can avoid this aggregation and increase its activity relative to PDT. Silica porous nanoparticles are chosen here as a matrix to host MB. The size and pore geometry are tuned in order to decrease MB leaching while maintaining good singlet oxygen generation and colloidal stability for further applications in nanomedicine. In addition, phenyl functions are grafted on the pores of the silica matrix in order to avoid MB aggregation, thereby increasing the activity of the photosensitizer in the singlet oxygen generation. DFT calculations give insight in the structure of the aggregation of the MB units, and the roles of water and organic environments are investigated through time-dependent calculations on UV-vis spectra. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous nanospheres are highly regarded for their applications in nanomedicine, optical devices, batteries, nanofiltration, and heterogeneous catalysis. In the last field, the dendritic morphology, which favors molecular diffusion, is a very important morphology known for silica, but not yet for carbon. A one‐pot, easy, and scalable co‐sol–gel route by using the triphasic resol–surfactant–silica system is shown to yield the topologies of dendritic and core–shell–corona mesoporous sister nanospheres by inner radial phase speciation control on a mass‐transfer‐limited process, depending on the relative polycondensation rates of the resol polymer and silica phases. The trick was the use of polyolamines with different catalytic activities on each hard phase polycondensation. The self‐entanglement of phases is produced at the {O−, S+, I−} organic–surfactant–inorganic interface. Mono‐ and biphasic mesoporous sister nanospheres of carbon and/or silica are derivatized from each mother nanospheres and called “syntaxic” because of similar sizes and mirrored morphologies. Comparing these “false twins”, or yin and yang mesoporous nanospheres, functionalized by sulfonic groups provides evidence of the superiority of the dendritic topologies and the absence of a shell on the diffusion‐controlled catalytic alkylation of m‐cresol. [ABSTRACT FROM AUTHOR]

Bio-inspired diethylenetriamine–zinc(ii) complexes were anchored into the nanopores of hexagonal mesoporous MCM41-like silicas targeting a carbamate free and low temperature CO2 recycling process. A step-by-step approach was adopted to perform an in situ synthesis in order to mimic the zinc finger of carbonic anhydrases, the fastest family of enzymes. In the presence of a surface-masking pattern of TMA+ ions, some silanol groups were capped using grafted trimethylsilyl functions, TMSgr, (gr for grafted). After removing the masking ions, a tridentate diethylenetriamine ligand was anchored using diethylenetriamine propyltrimethoxysilane. The so-called DETAan ligands (an for anchored) were partially monoprotonated using either cyclohexane or isopropanol as a solvent. Nonetheless, up to two thirds of them were metallated by Zn(ii) ions, leading to the targeted anchored zinc finger mimic [Zn(DETAan)L]+(L = Cl− or OH−). CO2 is then adsorbed at room temperature and in humid ambient air by the formation of an intermediate hydrogenocarbonate–zinc complex. Specific IR signatures at 1330 and 1400 cm−1 together with characteristic C 1s and Zn 2p3/2 XPS binding energies at 286.4 and 1024.6 eV advocate for a rather symmetrical bidentate [η2-CO3] structural unit in the anchored complex [Zn(DETAan)(η2-HCO3*)]+, where the Zn(ii) ion is most likely pentacoordinated. The internal pH value varied by less than 0.5 depending on the metal reacting with the DETAan ligand and its ability to generate HCO3−, due to the buffering effect of surface silanol and amino groups according to the level of protonation of the DETA moieties measured from the N 1s XPS spectra. In contrast to nitrate ions, chloride ions were found to inhibit the formation of hydrogenocarbonate. [ABSTRACT FROM AUTHOR]

Two new tetranuclear compounds with a formula [MnIII4(μ-O)2(μ-4-RC6H4COO)7−m(L)2m(phen)2](ClO4)1+m, where R = MeO or tBu and m = 0 or 1, were synthesised and studied structurally and magnetically. The core of these compounds comprises a central Mn2O2 rhombus to which two terminal ions are attached – one to each oxo bridge. There are two types of bridges that alternately bind the central and terminal ions, those having a triple (μ-O)(μ-RCOO)2 or a double (μ-O)(μ-RCOO) bridge. The fit of the magnetic data of analogous compounds has so far been performed considering two different magnetic interactions, that between central ions (J1) and those between terminal and central ions (Jct), leading to ground states with ST = 2 or 3, or to five energetically degenerate ground states with ST = 0–4, depending on the J1/Jct ratio. In contrast, the compounds presented herein show an isolated ST = 0 ground state, and it was necessary to distinguish the two types of magnetic interactions between central and terminal ions (J2 and J3) to achieve a good fit of the experimental data. The differentiation of these interactions causes a spin state redistribution: the degeneration of ST = 0–4 breaks and the states with ST≠ 0 become unstable as J2 and J3 become more different. Nevertheless, the assignment of these states to a particular spin configuration was unachievable because the composition of these states changes upon decreasing the J3/J2 ratio. The importance of considering the relative orientation of Jahn–Teller axes is also highlighted. [ABSTRACT FROM AUTHOR]

A family of new MnII compounds, consisting of seven dinuclear, three mononuclear, and four trinuclear ones, were synthesised using benzoic acid derivatives n-RC6H4COOH, where n-R = 2-MeO, 3-MeO, 4-MeO, or 4-tBu, and 2,2′-bipyridine (bpy) or 1,10-phenantroline (phen) as blocking ligands. The crystal structures of nine of these compounds and the magnetic studies of all of them are reported here. Each type of compound was formed depending on the presence or absence of ClO4− ions, the solvent used, and/or the presence of a small amount of water in the reaction medium. The use of the tert-buthylbenzoate ligand gave unexpected results, very likely due to the steric hindrance caused by the voluminous tBu groups. The EPR spectra of each type of compound give some peculiar features that allow its identification. Attempts to fit these spectra have been made in order to determine the ZFS parameters, D and E, of the MnII ion (for mononuclear and dinuclear systems) or of the ground state (for trinuclear systems). For trinuclear systems, the single-ion ZFS parameters estimated from those of the ground state provided a good simulation of the EPR spectra of these compounds. The EPR signals observed in each case have been rationalised according to the energy level distribution and the plausible population in the excited states. In some particular situations, the sign of DMn could be determined from the fit of the EPR spectra of the antiferromagnetic dinuclear compounds, the source of the difference between the spectra lying in the second excited state. [ABSTRACT FROM AUTHOR]