Dynamics of 8CB confined into porous silicon probed by incoherent neutron backscattering experiments

Confinement in the nanochannels of porous silicon strongly affects the phase behavior of the archetype liquid-crystal 4-n-octyl-4-cyanobiphenyl (8CB). A very striking phenom- enon is the development of a short-range smectic order, which occurs on a very broad temperature range. It suggests in this case that quenched disorder effects add to usual finite size and surface interaction effects. We have monitored the temperature variation of the molecular dynamics of the confined fluid by incoherent quasielastic neutron scat- tering. A strongly reduced mobility is observed at the highest temperatures in the liquid phase, which suggests that the interfacial molecular dynamics is strongly hindered. A continuously increasing slowdown appears on cooling together with a progressive growth of the static correlation lengt

Multifunctional approach to improve water oxidation performance with MOF-based photoelectrodes

Metal-Organic Frameworks (MOFs) are a group of compounds with high porosity and diverse capabilities in photoelectrochemistry. The use of these compounds as photocatalysts and photoelectrodes is still a strong challenge due to bulk and surface recombination issues. To solve this problem, we applied a dual strategy to simultaneously enhance charge separation and catalytic activity in MIL-125-NH2 and UIO-66-NH2 MOF photocatalysts. Mesoporous TiO2 was used as electron-selective contact on the MOF surface (MOF/TiO2) to minimize bulk recombination. On the other hand, to increase the MOF catalytic activity for water oxidation, a well-matched Co3(PO4)2 (CoPi) co-catalyst (CoPi/MOF/TiO2) was used. The obtained results showed that CoPi and TiO2 were introduced in the MOF structure. The (CoPi/MOF/TiO2) photoelectrodes showed a photocurrent density 26 times higher compared to the reference MOF at 1.23 V vs. RHE for PEC water oxidation of artificial seawater, validating the developed strategy for further photocatalytic and photoelectrochemical applications.Funding for open access charge: CRUE-Universitat Jaume IWe acknowledge with appreciation the financial support from the University of Isfahan and Ministry of Science, Research and Technology Center for International Scientific Studies and Collaboration (CISSC). SG acknowledges the financial support from the Ministerio de Ciencia, Innovación y Universidades of Spain through funded project ENE2017-85087-C3-1-R

Stimuli-responsive nanomaterials for controlled delivery by light, magnetic and electrical triggers

The use of nanomaterials for biomedical applications is an emerging and important field. This is particularly true of advancements in targeted and controlled drug delivery, which offer several important improvements over traditional drug administration. The clinical efficacy of small-molecule therapeutics is currently limited by many factors, including: poor solubility, inefficient cellular uptake, overly rapid renal clearance and an inability to target only desired locations such as diseased tissues. The use of nanocarriers for drug delivery may greatly improve the efficacy over traditional therapeutics by lowering the total dosage, limiting the exposure to affected areas only, and giving greater temporal control over drug elution. These materials often make use of both organic and inorganic components, exploiting the unique and useful properties of each constituent to achieve novel, synergistic functions. This dissertation presents a study of nanocomposites comprising the three most important materials in this field: titania, iron oxides and polypyrrole. Titania is a strong photocatalyst, iron oxides provide useful responses to applied magnetic fields, and polypyrrole is a polymer with unique electrochemical properties. Studies in this dissertation were aimed at combining these three materials to create a novel structure that is responsive towards light, magnetic fields and electrical stimulation to serve as an enabling platform for the loading and release of biologically interesting compounds. These nanomaterials have been paired with amino acids L-lysine and L-glutamic acid, two organic molecules of interest due to their ability to bind to DNA and proteins, and to form prodrugs that exhibit enhanced performance compared to traditionally administered medicines. Two model compounds have been loaded and released on these carriers: Ketoprofen, an important anti-inflammatory that is traditionally hindered by its limited cellular uptake levels; and fluorescein isothiocyanate, a fluorescent dye molecule that is a common tool used in this field for nanocarrier location and easy visualisation of release-related kinetics. First, an investigation into the effect of pH on the binding of amino acids to titania, iron oxide and polypyrrole is presented with a view towards optimising the functionalised material for subsequent loading and release of the model drugs (in this case, amine-reactive molecules). The release mechanism of photo-activated TiO2 is studied in detail with a particular focus on the competition between the cleavage of bonds versus organic degradation on the catalyst’s surface. Both mechanisms are currently reported in literature and studies were aimed at identifying the more dominant pathway in the system developed alongside understanding the crucial role of reaction time scales on this photochemistry. Then, the pH-tuneable flocculation of the amino acid-functionalised nanoparticles via electrostatic attractions is exploited to create a novel, anisotropic assembly of iron oxides. These filaments display a dynamic and unique response towards a rotating magnetic field by creating local microscale vortices. This motion is used to enhance local delivery rate of molecules through magnetic-field triggered microscale mixing. Finally, this anisotropic iron oxide structure is combined with polypyrrole to create a unique, novel material that possesses directional conductivity, a photothermal response, and magnetic field-triggered release of loaded molecules at enhanced and controllable rates compared with traditional diffusion-limited systems

Non-precious Metal Catalysts for Acetic Acid Reduction

Acetic acid (AA) hydroconversion was studied over various monometallic (Fe, Co, Ni, Cu, Zn, Pt) and bimetallic (doped with In as second, guest metal) catalysts loaded on a highly mesoporous, fumed silica support. The transformations were investigated in a fixed bed, flow-through reactor in temperature range of 240-380°C using hydrogen flow at 21bar total pressure. The catalyst precursors were activated in H2 flow at 21bar and 450°C as routine pre-treatment. Catalytic performances of the studied metal catalysts have nothing in common. Activities and the yields of main products contrast strikingly. Diversity of catalytic behaviour reflects the complexity of the surface reaction network. Contrary to the highly ethanol selective Co or Cu forms, over Ni catalyst mainly methane was produced. Indium doping can completely eliminate the hydrodecarbonylation activity and turn to the consecutive reduction route resulting in high ethanol yield. Metallic phases of different peculiarities can offer promising contacts for upgrading various oxygenates obtainable from biomass degradation

Incorporating Poly(3-hexyl thiophene) into Orthogonally Aligned Cylindrical Nanopores of Titania for Optoelectronics

The incorporation of hole conducting polymer poly(3-hexyl thiophene) (P3HT) into the 8-9 nm cylindrical nanopores of titania is investigated using films with a unique orthogonally oriented hexagonal close packed mesostructure. The films are synthesized using evaporation induced self-assembly (EISA) with Pluronic triblock copolymer F127 as the structure directing agent. The orthogonally oriented cylindrical nanopore structure was chosen over a cubic structure because confinement in uniform cylindrical channels is hypothesized to enhance hole conductivity of P3HT by inducing local polymer chain ordering. Orthogonal orientation of the cylindrical nanopores is achieved by modifying the substrate (FTO-coated glass slides) with crosslinked F127. After thermal treatment to remove organic templates from the films, P3HT is infiltrated into the nanopores by spin coating a 1 wt% P3HT solution in chlorobenzene onto the titania films followed by thermal annealing under vacuum at 200 °C. The results show that infiltration is essentially complete after 30 minutes of annealing, with little or no further infiltration thereafter. A final infiltration depth of ~14 nm is measured for P3HT into the nanopores of titania using neutron reflectometry measurements. Photoluminescence measurements demonstrate that charge transfer at the P3HT-TiO2 interface improves as the P3HT is infiltrated into the pores, suggesting that an active organic-inorganic heterojuction is formed in the materials

Electrochemical capacitance and ionic transport in the mesoporous shell of a hierarchical porous core-shell carbon structure

A three-dimensional (3D) hierarchical porous carbon structure was prepared with possible variations in porosity at three levels of length scales. The carbon structure was template-synthesized from a core-shell silica sphere assembly. The as-synthesized carbon featured a semi-ordered porous structure with hollow macro-cores (330 nm) surrounded by a mesoporous shell containing uniform pores of 3.9 nm and distinct interstitial space between the core-shell domains. The mesoporous shell thickness was stepwise increased from 0, 25, 50 to 100 nm while keeping an identical core size to create a family of hierarchical porous structures for a systematic investigation of electrochemical capacitance and ionic transport. The shell thickness affected the overall porosity and relative porosities of the shell, core, and interstitial regions. A thicker mesoporous shell possessed a higher surface area which led to a proportional increase in electrochemical capacitance which can be fully realised at low scan rates. For the carbon structure with the maximum shell thickness of 100 nm, electrochemical capacitance per unit area and power density declined at high scan rates and high currents when ionic transport through long mesopores became limiting. The power density of the better as-synthesized porous carbon was up to 11.7 kW kg-1 when the corresponding energy density was 5.9 W h kg-1. © 2011 The Royal Society of Chemistry.postprin

Characterization and Performance Evaluation of Dye Sensitized Solar Cell Using Nanostructured TiO 2

Metal-free organic sensitizer consisting of donor, electron conducting, and anchoring anhydride groups was engineered at molecular level and synthesized. Dye sensitized solar cells based on conjugated naphthalene dye were fabricated using nanoporous electrode. Photoelectrodes with a 7 μm thick nanoporous layer and a 5 μm thick light-scattering layer were used to fabricate dye sensitized solar cells. DSSCs were fabricated in a FTO/nc-TiO2/organic dye/I-/I3-/Pt/FTO device geometry. Dye sensitized solar cell was characterized by current density-voltage (J-V) measurement. All current-voltage (I-V) measurements were done under 100 mW/cm2 light intensity and AM 1.5 conditions. The photovoltaic data revealed a short circuit photocurrent density of 1.86 mA/cm2, an open circuit voltage of 430 mV, and a fill factor of 0.63, corresponding to an overall conversion efficiency of 0.53%

Control of Pore and Wire Dimensions in Mesoporous Metal Nanowire Networks through Curvature Modulation in Lipid Templates:Implications for Use as Electrodes

This paper presents the production of mesoporous metals with periodic 3D nanostructures, showing control over the lattice parameter and therefore pore and wire dimensions. The materials have "single diamond"(Fd3m) symmetry and are produced by deposition within a "cubic phase"template of the lipid phytantriol, in a process previously published. The current work shows a mechanism for tuning the nanoscale dimensions of the metal by the addition of a cosurfactant that progressively reduces the lipid bilayer curvature in the template. This swells its lattice parameter and therefore that of the deposited metal. Mesoporous platinum samples were characterized using X-ray scattering, electron microscopy, and electrochemical analysis. The structures exhibit unit cell sizes ranging from 13 to 20 nm, with wire thicknesses from 3.0 to 5.3 nm and estimated pore dimensions from 6.2 to 8.8 nm. The size control in these materials provides a mechanism for control of electrochemical behavior in electrocatalysis and sensors. Furthermore, the use of the templates in other metal and semiconductor materials suggests that size control offers possibilities for metamaterials with designed optoelectronic properties. </p

Operando Studies of Aerosol-Assisted Sol–Gel Catalyst Synthesis via Combined Optical Trapping and Raman Spectroscopy

New insights have been gained into chemical transformations occurring in the initial stages of aerosol-assisted sol–gel (AASG) synthesis of catalysts. This has been achieved through the combined application of optical trapping and Raman spectroscopy. AASG is an emerging technology in catalyst manufacturing that presents numerous advantages over conventional approaches, including the ability to access unique catalyst morphologies. However, the processes occurring during synthesis are largely inferred from bulk-phase analyses due to challenges in conducting in situ or operando measurements on moving aerosols within a flow tube. Herein, these obstacles are overcome through Raman spectroscopic interrogation of a single aerosol droplet constrained within an optical trap, which acts as a direct analogue for a particle moving along a flow tube. These studies represent the first operando investigations of AASG synthesis. The synthesis of Ni/Al2O3 catalysts has been studied, with spectroscopic interrogation conducted on each component of the precursor synthesis solution, where possible, up to and including a mixture containing all components necessary for catalyst synthesis. Raman spectroscopy confirms the formation of stable self-assembled macrostructures within the aerosol and provides direct insights into the reaction mechanisms. Crucially, evidence was obtained allowing alternative reaction pathways to be postulated within the confined environment of an aerosol droplet in comparison to bulk-phase syntheses. In aerosols where nickel was not present, but contained all other components, isothermal room-temperature studies showed the formation of stable but unreactive droplets of ∼1 μm, which were proposed to contain micelle-type structures. Upon heating, initial gelation transformations were seen to be achieved at temperatures higher than ∼56 °C. Notably, little loss of spectral intensity corresponding to the C–H stretch (ethanol) was observed from the heated aerosol, implying that evaporation is not a prerequisite for the reaction. When nickel is present in the synthesis solution reactive transformations occur at room temperature, proposed to result in a continuous Al–O–Ni–NO3 structure; a more rapid transformation takes place at elevated temperatures. These results provide the first direct evidence of the processes occurring within aerosols during AASG and shed new light on the mechanistic understanding of this technology. This therefore facilitates the design of new synthetic approaches and hence the production of catalysts and other materials with enhanced properties