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1.
Small ; : e2404364, 2024 Aug 08.
Artículo en Inglés | MEDLINE | ID: mdl-39115351

RESUMEN

Ultrahigh-temperature Joule-heating of carbon nanostructures opens up unique opportunities for property enhancements and expanded applications. This study employs rapid electrical Joule-heating at ultrahigh temperatures (up to 3000 K within 60 s) to induce a transformation in nanocarbon aerogels, resulting in highly graphitic structures. These aerogels function as versatile platforms for synthesizing customizable metal oxide nanoparticles while significantly reducing carbon emissions compared to conventional furnace heating methods. The thermal conductivity of the aerogel, characterized by Umklapp scattering, can be precisely adjusted by tuning the heating temperature. Utilizing the aerogel's superhydrophobic properties enables its practical application in filtration systems for efficiently separating toxic halogenated solvents from water. The hierarchically porous aerogel, featuring a high surface area of 607 m2 g-1, ensures the uniform distribution and spacing of embedded metal oxide nanoparticles, offering considerable advantages for catalytic applications. These findings demonstrate exceptional catalytic performance in oxidative desulfurization, achieving a 98.9% conversion of dibenzothiophene in the model fuel. These results are corroborated by theoretical calculations, surpassing many high-performance catalysts. This work highlights the pragmatic and highly efficient use of nanocarbon structures in nanoparticle synthesis under ultrahigh temperatures, with short heating durations. Its broad implications extend to the fields of electrochemistry, energy storage, and high-temperature sensing.

2.
Biomater Sci ; 2024 Aug 29.
Artículo en Inglés | MEDLINE | ID: mdl-39206560

RESUMEN

A key factor in biomineralization is the use of organic molecules to direct the formation of inorganic materials. However, identification of molecules that can selectively produce the calcium carbonate polymorphs calcite or aragonite has proven extremely challenging. Here, we use a phage display approach to identify proteins - rather than the short peptides typically identified using this method - that can direct calcium carbonate formation. A 1.3 × 1010 library of Affimer proteins was displayed on modified M13 phage, where an Affimer is a ≈13 kDa protein scaffold that displays two variable regions of 9-13 residues. The phage displaying the Affimer library were then screened in binding assays against calcite and aragonite at pH 7.4, and four different strongly-binding proteins were identified. The two aragonite-binding proteins generated aragonite when calcium and magnesium ions were present at a 1 : 1 ratio, while the calcite-binding proteins produce magnesium-calcite under the same conditions. Calcite alone formed in the presence of all four proteins in the absence of magnesium ions. In combination with molecular dynamics simulations to evaluate the conformations of the proteins in solution, this work demonstrates the importance of conformation in polymorph control, and highlights the importance of magnesium ions, which are abundant in seawater, to reduce the energetic barriers associated with aragonite formation.

3.
Dalton Trans ; 53(16): 6983-6992, 2024 Apr 23.
Artículo en Inglés | MEDLINE | ID: mdl-38563124

RESUMEN

[Fe(bpp)2][ClO4]2 (bpp = 2,6-bis{pyrazol-1-yl}pyridine; monoclinic, C2/c) is high-spin between 5-300 K, and crystallises with a highly distorted molecular geometry that lies along the octahedral-trigonal prismatic distortion pathway. In contrast, [Ni(bpp)2][ClO4]2 (monoclinic, P21) adopts a more regular, near-octahedral coordination geometry. Gas phase DFT minimisations (ω-B97X-D/6-311G**) of [M(bpp)2]2+ complexes show the energy penalty associated with that coordination geometry distortion runs as M2+ = Fe2+ (HS) ≈ Mn2+ (HS) < Zn2+ ≈ Co2+ (HS) ≲ Cu2+ ≪ Ni2+ ≪ Ru2+ (LS; HS = high-spin, LS = low-spin). Slowly crystallised solid solutions [FexNi1-x(bpp)2][ClO4]2 with x = 0.53 (1a) and 0.74 (2a) adopt the P21 lattice, while x = 0.87 (3a) and 0.94 (4a) are mixed-phase materials with the high-spin C2/c phase as the major component. These materials exhibit thermal spin-transitions at T½ = 250 ± 1 K which occurs gradually in 1a, and abruptly and with narrow thermal hysteresis in 2a-4a. The transition proceeds to 100% completeness in 1a and 2a; that is, the 26% Ni doping in 2a is enough to convert high-spin [Fe(bpp)2][ClO4]2 into a cooperative, fully SCO-active material. These results were confirmed crystallographically for 1a and 2a, which revealed similarities and differences between these materials and the previously published [FexNi1-x(bpp)2][BF4]2 series. Rapidly precipitated powders with the same compositions (1b-4b) mostly resemble 1a-4a, except that 2b is a mixed-phase material; 2b-4b also contain a fraction of amorphous solid in addition to the two crystal phases. The largest iron fraction that can be accommodated by the P21 phase in this system is 0.7 ± 0.1.

4.
ACS Appl Mater Interfaces ; 16(10): 12467-12478, 2024 Mar 13.
Artículo en Inglés | MEDLINE | ID: mdl-38423989

RESUMEN

Porous organic cages (POCs) are nanoporous materials composed of discrete molecular units that have uniformly distributed functional pores. The intrinsic porosity of these structures can be tuned accurately at the nanoscale by altering the size of the porous molecules, particularly to an optimal size of 3.6 Å, to harness the kinetic quantum sieving effect. Previous research on POCs for isotope separation has predominantly centered on differences in the quantities of adsorbed isotopes. However, nuclear quantum effects also contribute significantly to the dynamics of the sorption process, offering additional opportunities for separating H2 and D2 at practical operational temperatures. In this study, our investigations into H2 and D2 sorption on POC samples revealed a higher uptake of D2 compared to that of H2 under identical conditions. We employed quasi-elastic neutron scattering to study the diffusion processes of D2 and H2 in the POCs across various temperature and pressure ranges. Additionally, neutron Compton scattering was utilized to measure the values of the nuclear zero-point energy of individual isotopic species in D2 and H2. The results indicate that the diffusion coefficient of D2 is approximately one-sixth that of H2 in the POC due to the nuclear quantum effect. Furthermore, the results reveal that at 77 K, D2 has longer residence times compared to H2 when moving from pore to pore. Consequently, using the kinetic difference of H2 and D2 in a porous POC system enables hydrogen isotope separation using a temperature or pressure swing system at around liquid nitrogen temperatures.

5.
J Am Chem Soc ; 146(1): 159-169, 2024 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-38159061

RESUMEN

Flash Joule heating of highly porous graphene oxide (GO) aerogel monoliths to ultrahigh temperatures is exploited as a low carbon footprint technology to engineer functional aerogel materials. Aerogel Joule heating to up to 3000 K is demonstrated for the first time, with fast heating kinetics (∼300 K·min-1), enabling rapid and energy-efficient flash heating treatments. The wide applicability of ultrahigh-temperature flash Joule heating is exploited in a range of material fabrication challenges. Ultrahigh-temperature Joule heating is used for rapid graphitic annealing of hydrothermal GO aerogels at fast time scales (30-300 s) and substantially reduced energy costs. Flash aerogel heating to ultrahigh temperatures is exploited for the in situ synthesis of ultrafine nanoparticles (Pt, Cu, and MoO2) embedded within the hybrid aerogel structure. The shockwave heating approach enables high through-volume uniformity of the formed nanoparticles, while nanoparticle size can be readily tuned through controlling Joule-heating durations between 1 and 10 s. As such, the ultrahigh-temperature Joule-heating approach introduced here has important implications for a wide variety of applications for graphene-based aerogels, including 3D thermoelectric materials, extreme temperature sensors, and aerogel catalysts in flow (electro)chemistry.

6.
Cryst Growth Des ; 23(12): 8978-8990, 2023 Dec 06.
Artículo en Inglés | MEDLINE | ID: mdl-38076525

RESUMEN

The ability to control crystal nucleation through the simple addition of a nucleating agent (nucleant) is desirable for a huge range of applications. However, effective nucleating agents are known for only a small number of systems, and many questions remain about the mechanisms by which they operate. Here, we explore the features that make an effective nucleant and demonstrate that the biological material hair-which naturally possesses a chemically and topographically complex surface structure-has excellent potential as an effective nucleating agent. Crystallization of poorly soluble compounds in the presence of hairs from a range of mammals shows that nucleation preferentially occurs at the cuticle step edges, while a novel microdroplet-based methodology was used to quantify the nucleating activities of different hairs. This showed that the activities of the hairs can be tuned over a wide range using chemical treatments. Analysis of the hair structure and composition using atomic force microscopy, scanning ion conductance microscopy, and X-ray photoelectron spectroscopy demonstrates that surface chemistry, surface topography, and surface charge all act in combination to create effective nucleation sites. This work therefore contributes to our understanding of heterogeneous nucleating agents and shows that surface topography as well as surface chemistry can be used in the design or selection of universal nucleating agents.

7.
Chem Sci ; 14(24): 6705-6715, 2023 Jun 21.
Artículo en Inglés | MEDLINE | ID: mdl-37350829

RESUMEN

The cylindrical pores of track-etched membranes offer excellent environments for studying the effects of confinement on crystallization as the pore diameter is readily varied and the anisotropic morphologies can direct crystal orientation. However, the inability to image individual crystals in situ within the pores in this system has prevented many of the underlying mechanisms from being characterized. Here, we study the crystallization of calcium sulfate within track-etched membranes and reveal that oriented gypsum forms in 200 nm diameter pores, bassanite in 25-100 nm pores and anhydrite in 10 nm pores. The crystallization pathways are then studied by coating the membranes with an amorphous titania layer prior to mineralization to create electron transparent nanotubes that protect fragile precursor materials. By visualizing the evolutionary pathways of the crystals within the pores we show that the product single crystals derive from multiple nucleation events and that orientation is determined at early reaction times. Finally, the transformation of bassanite to gypsum within the membrane pores is studied using experiment and potential mean force calculations and is shown to proceed by localized dissolution/reprecipitation. This work provides insight into the effects of confinement on crystallization processes, which is relevant to mineral formation in many real-world environments.

8.
Adv Sci (Weinh) ; : e2203759, 2022 Nov 20.
Artículo en Inglés | MEDLINE | ID: mdl-36403251

RESUMEN

Calcium carbonate biomineralization is remarkable for the ability of organisms to produce calcite or aragonite with perfect fidelity, where this is commonly attributed to specific anionic biomacromolecules. However, it is proven difficult to mimic this behavior using synthetic or biogenic anionic organic molecules. Here, it is shown that cationic polyamines ranging from small molecules to large polyelectrolytes can exert exceptional control over calcium carbonate polymorph, promoting aragonite nucleation at extremely low concentrations but suppressing its growth at high concentrations, such that calcite or vaterite form. The aragonite crystals form via particle assembly, giving nanoparticulate structures analogous to biogenic aragonite, and subsequent growth yields stacked aragonite platelets comparable to structures seen in developing nacre. This mechanism of polymorph selectivity is captured in a theoretical model based on these competing nucleation and growth effects and is completely distinct from the activity of magnesium ions, which generate aragonite by inhibiting calcite. Profiting from these contrasting mechanisms, it is then demonstrated that polyamines and magnesium ions can be combined to give unprecedented control over aragonite formation. These results give insight into calcite/aragonite polymorphism and raise the possibility that organisms may exploit both amine-rich organic molecules and magnesium ions in controlling calcium carbonate polymorph.

9.
IUCrJ ; 9(Pt 5): 538-543, 2022 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-36071805

RESUMEN

Recent advances in X-ray instrumentation and sample injection systems have enabled serial crystallography of protein nanocrystals and the rapid structural analysis of dynamic processes. However, this progress has been restricted to large-scale X-ray free-electron laser (XFEL) and synchrotron facilities, which are often oversubscribed and have long waiting times. Here, we explore the potential of state-of-the-art laboratory X-ray systems to perform comparable analyses when coupled to micro- and millifluidic sample environments. Our results demonstrate that commercial small- and wide-angle X-ray scattering (SAXS/WAXS) instruments and X-ray diffractometers are ready to access samples and timescales (≳5 ms) relevant to many processes in materials science including the preparation of pharmaceuticals, nanoparticles and functional crystalline materials. Tests of different X-ray instruments highlighted the importance of the optical configuration and revealed that serial WAXS/XRD analysis of the investigated samples was only possible with the higher flux of a microfocus setup. We expect that these results will also stimulate similar developments for structural biology.

10.
Chem Mater ; 34(11): 4910-4923, 2022 Jun 14.
Artículo en Inglés | MEDLINE | ID: mdl-35722202

RESUMEN

Incorporation of guest additives within inorganic single crystals offers a unique strategy for creating nanocomposites with tailored properties. While anionic additives have been widely used to control the properties of crystals, their effective incorporation remains a key challenge. Here, we show that cationic additives are an excellent alternative for the synthesis of nanocomposites, where they are shown to deliver exceptional levels of incorporation of up to 70 wt % of positively charged amino acids, polymer particles, gold nanoparticles, and silver nanoclusters within inorganic single crystals. This high additive loading endows the nanocomposites with new functional properties, including plasmon coupling, bright fluorescence, and surface-enhanced Raman scattering (SERS). Cationic additives are also shown to outperform their acidic counterparts, where they are highly active in a wider range of crystal systems, owing to their outstanding colloidal stability in the crystallization media and strong affinity for the crystal surfaces. This work demonstrates that although often overlooked, cationic additives can make valuable crystallization additives to create composite materials with tailored composition-structure-property relationships. This versatile and straightforward approach advances the field of single-crystal composites and provides exciting prospects for the design and fabrication of new hybrid materials with tunable functional properties.

11.
Chem Sci ; 12(28): 9839-9850, 2021 Jul 21.
Artículo en Inglés | MEDLINE | ID: mdl-34349958

RESUMEN

Nanocarriers have tremendous potential for the encapsulation, storage and delivery of active compounds. However, current formulations often employ open structures that achieve efficient loading of active agents, but that suffer undesired leakage and instability of the payloads over time. Here, a straightforward strategy that overcomes these issues is presented, in which protein nanogels are encapsulated within single crystals of calcite (CaCO3). Demonstrating our approach with bovine serum albumin (BSA) nanogels loaded with (bio)active compounds, including doxorubicin (a chemotherapeutic drug) and lysozyme (an antibacterial enzyme), we show that these nanogels can be occluded within calcite host crystals at levels of up to 45 vol%. Encapsulated within the dense mineral, the active compounds are stable against harsh conditions such as high temperature and pH, and controlled release can be triggered by a simple reduction of the pH. Comparisons with analogous systems - amorphous calcium carbonate, mesoporous vaterite (CaCO3) polycrystals, and calcite crystals containing polymer vesicles - demonstrate the superior encapsulation performance of the nanogel/calcite system. This opens the door to encapsulating a broad range of existing nanocarrier systems within single crystal hosts for the efficient storage, transport and controlled release of various active guest species.

12.
ACS Appl Mater Interfaces ; 13(30): 36201-36212, 2021 Aug 04.
Artículo en Inglés | MEDLINE | ID: mdl-34291894

RESUMEN

Joule heating studies on nanoparticle/nanocarbon hybrid aerogels have been reported, but systematic investigations on hydrotalcite-derived catalysts supported onto reduced graphene oxide (rGO) aerogels are rare. In this study, hydrotalcite-derived Cu-Al2O3 nanoparticles were incorporated into a porous and multifunctional rGO aerogel support for fabricating electrically conducting Cu-Al2O3/rGO hybrid aerogels, and their properties were investigated in detail. The hybridization of Cu-Al2O3 with a 3D nanocarbon support network imparts additional functionalities to the widely used functional inorganic nanoparticles, such as direct electrical framework heating and easy regeneration and separation of spent nanoparticles, with well-spaced nanoparticle segregation. 3D variable-range hopping model fitting confirmed that electrons were able to reach the entire aerogel to enable uniform resistive heating. The conductivity of the nanocarbon support framework facilitates uniform and fast heating (up to 636 K/min) of the embedded nanoparticles at very low energy consumption, while the large porosity and high thermal conductivity enable efficient heat dissipation during natural cooling (up to 336 K/min). The thermal stability of the hybrid aerogel was demonstrated by repeated heating/cooling cycling at different temperatures that were relevant to important industrial applications. The facile synthetic approach can be easily adapted to fabricate other types of multifunctional nanoparticle/nanocarbon hybrid aerogels, such as the MgAl-MMO/rGO aerogel and the Ni-Al2O3/rGO aerogel. These findings open up new routes to the functionalization of inorganic nanoparticles and extend their application ranges that involve electrical/thermal heating, temperature-dependent catalysis, sorption, and sensing.

13.
J Colloid Interface Sci ; 594: 101-112, 2021 Jul 15.
Artículo en Inglés | MEDLINE | ID: mdl-33756358

RESUMEN

HYPOTHESIS: The properties of stable gold (Au) nanoparticle dispersions can be tuned to alter their activity towards biomembrane models. EXPERIMENTS: Au nanoparticle coating techniques together with rapid electrochemical screens of a phospholipid layer on fabricated mercury (Hg) on platinum (Pt) electrode have been used to moderate the phospholipid layer activity of Au nanoparticle dispersions. Screening results for Au nanoparticle dispersions were intercalibrated with phospholipid large unilamellar vesicle (LUV) interactions using a carboxyfluorescein (CF) leakage assay. All nanoparticle dispersions were characterised for size, by dynamic light scattering (DLS) and transmission electron microscopy (TEM). FINDINGS: Commercial and high quality home synthesised Au nanoparticle dispersions are phospholipid monolayer active whereas Ag nanoparticle dispersions are not. If Au nanoparticles are coated with a thin layer of Ag then the particle/lipid interaction is suppressed. The electrochemical assays of the lipid layer activity of Au nanoparticle dispersions align with LUV leakage assays of the same. Au nanoparticles of decreasing size and increasing dispersion concentration showed a stronger phospholipid monolayer/bilayer interaction. Treating Au nanoparticles with cell culture medium and incubation of Au nanoparticle dispersions in phosphate buffered saline (PBS) solutions removes their phospholipid layer interaction.


Asunto(s)
Nanopartículas del Metal , Electrodos , Oro , Fosfolípidos , Plata
14.
Chembiochem ; 22(8): 1430-1439, 2021 04 16.
Artículo en Inglés | MEDLINE | ID: mdl-33296552

RESUMEN

Matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) is widely used for the analysis of biomolecules. Label-assisted laser desorption/ionisation mass spectrometry (LALDI-MS) is a matrix-free variant of MALDI-MS, in which only analytes covalently attached to a laser desorption/ionisation (LDI) enhancer are detected. LALDI-MS has shown promise in overcoming the limitations of MALDI-MS in terms of sample preparation and MS analysis. In this work, we have developed a series of pyrene-based LDI reagents (LALDI tags) that can be used for labelling and LALDI-MS analysis of reducing carbohydrates from complex (biological) samples without the need for additional chemical derivatisation or purification. We have systematically explored the suitability of four pyrene-based LDI enhancers and three aldehyde-reactive handles, optimised sample preparation, and demonstrated the use of LALDI tags for the detection of lactose. We have also exemplified the potential of LALDI tags for labelling carbohydrates in biological samples by direct detection of lactose in cow's milk. These results demonstrate that LALDI-MS is a promising technique for the analysis of reducing carbohydrates in biological samples, and pave the way for the development of LALDI-MS for glycomics and diagnostics.


Asunto(s)
Carbohidratos/análisis , Pirenos/química , Estructura Molecular , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción
15.
Chem Sci ; 11(2): 355-363, 2020 Jan 14.
Artículo en Inglés | MEDLINE | ID: mdl-32874489

RESUMEN

Single crystals containing nanoparticles represent a unique class of nanocomposites whose properties are defined by both their compositions and the structural organization of the dispersed phase in the crystalline host. Yet, there is still a poor understanding of the relationship between the synthesis conditions and the structures of these materials. Here ptychographic X-ray computed tomography is used to visualize the three-dimensional structures of two nanocomposite crystals - single crystals of calcite occluding diblock copolymer worms and vesicles. This provides unique information about the distribution of the copolymer nano-objects within entire, micron-sized crystals with nanometer spatial resolution and reveals how occlusion is governed by factors including the supersaturation and calcium concentration. Both nanocomposite crystals are seen to exhibit zoning effects that are governed by the solution composition and interactions of the additives with specific steps on the crystal surface. Additionally, the size and shape of the occluded vesicles varies according to their location within the crystal, and therefore the solution composition at the time of occlusion. This work contributes to our understanding of the factors that govern nanoparticle occlusion within crystalline materials, where this will ultimately inform the design of next generation nanocomposite materials with specific structure/property relationships.

16.
ACS Appl Mater Interfaces ; 12(30): 33603-33612, 2020 Jul 29.
Artículo en Inglés | MEDLINE | ID: mdl-32602700

RESUMEN

Metal oxynitrides adopting the perovskite structure have been shown to be visible light-activated photocatalysts, and therefore, they have potential as self-cleaning materials where surface organic pollutants can be removed by photomineralization. In this work, we establish a route for the deposition of thin films for seven perovskite oxynitrides, CaTaO2N, SrTaO2N, BaTaO2N, LaTaON2, EuTaO2N, SrNbO2N, and LaNbON2, on quartz and alumina substrates using dip-coating of a polymer gel to form an amorphous oxide precursor film, followed by ammonolysis. The initially deposited oxide films were annealed at 800 °C, followed by ammonolysis at temperatures from 850 to 1000 °C. The perovskite oxynitride thin films were characterized using XRD and EDX, with band gaps determined using Tauc plots derived from UV-vis spectroscopic data. A cobalt oxide co-catalyst was deposited onto each film by drop casting, and the photocatalytic activity assessed under visible light using dichloroindophenol dye degradation in the presence of a sacrificial oxidant. The light source used was a solar simulator equipped with a 400 nm cut-off filter. The dye degradation test demonstrated photocatalytic activity in all samples except EuTaO2N and BaTaO2N. The three most active samples were SrNbO2N, CaTaO2N, and SrTaO2N. The cobalt oxide loading was optimized for these three films and found to be 0.3 µg cm-2. Further, catalytic tests were conducted using stearic acid degradation, and this found the film of SrNbO2N with the cobalt oxide co-catalyst to be the most active for complete mineralization of this model pollutant.

17.
Nat Commun ; 10(1): 5682, 2019 12 12.
Artículo en Inglés | MEDLINE | ID: mdl-31831739

RESUMEN

Acidic macromolecules are traditionally considered key to calcium carbonate biomineralisation and have long been first choice in the bio-inspired synthesis of crystalline materials. Here, we challenge this view and demonstrate that low-charge macromolecules can vastly outperform their acidic counterparts in the synthesis of nanocomposites. Using gold nanoparticles functionalised with low charge, hydroxyl-rich proteins and homopolymers as growth additives, we show that extremely high concentrations of nanoparticles can be incorporated within calcite single crystals, while maintaining the continuity of the lattice and the original rhombohedral morphologies of the crystals. The nanoparticles are perfectly dispersed within the host crystal and at high concentrations are so closely apposed that they exhibit plasmon coupling and induce an unexpected contraction of the crystal lattice. The versatility of this strategy is then demonstrated by extension to alternative host crystals. This simple and scalable occlusion approach opens the door to a novel class of single crystal nanocomposites.


Asunto(s)
Biomineralización , Sustancias Macromoleculares/química , Nanocompuestos/química , Biomimética , Carbonato de Calcio/química , Cristalización , Glicoproteínas , Oro/química , Nanopartículas del Metal/química , Minerales/química , Tamaño de la Partícula , Proteínas
18.
Dalton Trans ; 48(28): 10619-10627, 2019 Jul 16.
Artículo en Inglés | MEDLINE | ID: mdl-31231727

RESUMEN

UV activated photocatalysts deposited using chemical vapour deposition have found commercial success as self-cleaning coatings. However, only limited work has been conducted on the use of the more recently discovered visible light activated photocatalysis for this application. Tantalum oxynitride is an established visible light photocatalyst, and in this paper we have investigated the ability of thin films of tantalum oxynitride to photocatalytically degrade a model organic pollutant, stearic acid, and therefore assess the coatings potential for self-cleaning applications. Thin films of tantalum oxide were formed using aerosol assisted chemical vapour deposition (AACVD) of tantalum ethoxide, and then converted into tantalum oxynitride through ammonolysis at temperatures between 550 °C and 750 °C. Investigation of the films using XRD, UV-vis spectroscopy and XAFS identify that amorphous tantalum oxynitride is formed during the ammonolysis, with complete conversion to TaON under conditions of 700 °C for 24 hours. The self-cleaning ability of this film was assessed using stearic acid as the model pollutant, with a degradation rate of 2.5(2) × 1013 molecules per min per cm2 when exposed to a 5-sun solar simulator, equipped with a UV cut-off filter. We therefore conclude that tantalum oxynitride thin films are able to act as self-cleaning coatings through visible light photocatalysis and that films of tantalum oxynitride can be synthesized using a scalable chemical vapour deposition route.

19.
Angew Chem Int Ed Engl ; 58(13): 4302-4307, 2019 Mar 22.
Artículo en Inglés | MEDLINE | ID: mdl-30673157

RESUMEN

In principle, incorporating nanoparticles into growing crystals offers an attractive and highly convenient route for the production of a wide range of novel nanocomposites. Herein we describe an efficient aqueous route that enables the spatially controlled occlusion of gold nanoparticles (AuNPs) within ZnO crystals at up to 20 % by mass. Depending on the precise synthesis protocol, these AuNPs can be (i) solely located within a central region, (ii) uniformly distributed throughout the ZnO host crystal or (iii) confined to a surface layer. Remarkably, such efficient occlusion is mediated by a non-ionic water-soluble polymer, poly(glycerol monomethacrylate)70 (G70 ), which is chemically grafted to the AuNPs; pendent cis-diol side groups on this steric stabilizer bind Zn2+ cations, which promotes nanoparticle interaction with the growing ZnO crystals. Finally, uniform occlusion of G70 -AuNPs within this inorganic host leads to faster UV-induced photodegradation of a model dye.

20.
ACS Biomater Sci Eng ; 5(6): 2778-2785, 2019 Jun 10.
Artículo en Inglés | MEDLINE | ID: mdl-33405610

RESUMEN

Oxidative stress caused by free radicals is one of the great threats to inflict intracellular damage. Here, we report a convenient approach to the synthesis, characterization, and evaluation of the radical activity of titanium-based composites. We have investigated the potential of natural antioxidants (curcumin, quercetin, catechin, and vitamin E) as radical scavengers and stabilizers. The titanium oxide composites were prepared via three steps including sol-gel synthesis, carboxylation, and esterification. The characterization of the titanium-phenol composites was carried out by FTIR, PXRD, UV-vis and SEM methods. The radical scavenging ability of the novel materials was evaluated using DPPH and an in vitro LPO assay using isolated rat liver mitochondria. The novel materials exhibit both a higher stability and an antioxidant activity in comparison to bare TiO2. It was found that curcumin and quercetin based composites show the highest antioxidant efficiency among the composites under study followed by catechin and vitamin E based materials. The results from an MTT assay carried out on the Caco-2 cell line indicate that the composites do not contribute to the cytotoxicity in vitro. This study demonstrates that a combination of powerful antioxidants with titanium dioxide can change its functional properties and provide a convenient strategy against oxidative stress.

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