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1.
ACS Appl Mater Interfaces ; 16(26): 33461-33474, 2024 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-38888106

RESUMO

The synthesis, physicochemical, and functional properties of composite solids resulting from the surface spread of oxidized indium species onto nanoplatelets of anatase were investigated. Both the size and the interaction between the indium- and titanium-containing components control the functional properties. In the reduction of CO2 to CO, the best samples have an indium content between ca. 2 and 5 mol % and showed an excess rate over the photo and thermo-alone processes above 33% and an energy efficiency of 1.3%. Subnanometric (monomeric and dimeric) indium species present relatively weak thermal catalytic response but strong thermo-photo promotion of the activity. A gradual change in functional properties was observed with the growth of the indium content of the solids, leading to a progressive increase of thermal activity but lower thermo-photo promotion. The study provides a well-defined structure-activity relationship rationalizing the dual thermo-photo properties of the catalysts and establishes a guide for the development of highly active and stable composite solids for the elimination and valorization of CO2.

2.
ACS Appl Mater Interfaces ; 16(23): 30157-30165, 2024 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-38808921

RESUMO

The synthesis and properties of stoichiometric, reduced, and Co-doped In2O3 are described in the light of several experimental techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet (UV)-visible spectroscopy, porosimetry, and density functional theory (DFT) methods on appropriate models. DFT-based calculations provide an accurate prediction of the atomic and electronic structure of these systems. The computed lattice parameter is linearly correlated with the experimental result in the Co concentration ranging from 1.0 to 5.0%. For higher Co concentrations, the theoretical-experimental analysis of the results indicates that the dopant is likely to be preferentially present at surface sites. The analysis of the electronic structure supports the experimental assignment of Co2+ for the doped material. Experiments and theory find that the presence of Co has a limited effect on the material band gap.

3.
ACS Sustain Chem Eng ; 11(9): 3896-3906, 2023 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-36911875

RESUMO

In this contribution, a series of Pd-promoted Nb-doped titania samples were essayed in the gas-phase thermo-photo production of syngas from methanol/water mixtures. The Pd loading was tested in the 0.1 to 2.5 wt % range, leading to the presence of metallic nanoparticles under reaction. Reaction rates exceeding 52 mmol H2 g-1 h-1 and quantum efficiencies above 33% were obtained. The optimum sample having a 0.5 wt % of Pd provided an outstanding synergy between light and heat under reaction conditions, facilitating the boost of activity with respect to the single-source processes and achieving high selectivity to syngas. The spectroscopic analysis of the physico-chemical ground of the activity unveiled that the noble metal interaction with the Nb-doped anatase support triggers a cooperative effect, promoting the evolution of formic acid-type methanol-derived carbon-containing species and rendering a significant enhancement of syngas production. The proposed thermo-photo system is thus a firm candidate to contribute to the new green circular economy.

4.
ACS Omega ; 6(40): 26108-26118, 2021 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-34660971

RESUMO

This research evaluated the potential photocatalytic efficiency of synthesized Cu-Fe/TiO2 photocatalysts against organic contaminants and biocontaminants through various synthesis methods (Cu-to-Fe ratio, metal loading, and calcination temperature) and reaction parameters (photocatalyst dose, irradiation time, and different initial methyl orange (MO) concentrations). In addition, the best photocatalysts were characterized through Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), differential reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS) analysis techniques. The best metal loading was 1 wt % with 5:5 Cu/Fe ratio and 300 °C calcination temperature (5Cu-5Fe/TiO2-300) having 97% MO decolorization. Further analysis indicates that the metal presence does not generate new channels for de-excitation but clearly affects the intensity and decreases charge recombination. The behavior of the photoluminescence intensity is (inversely) proportional to the activity behavior through the series, indicating that the main catalytic effect of Fe and Cu relates to charge recombination and that the Cu-Fe bimetallic catalyst optimizes such function. Moreover, the best-engineered photocatalysts asserted impactful bacteriostatic efficacy toward the tested Escherichia coli strain (in 30 min), and therefore, molecular docking studies were used to predict the inhibition pathway against E. coli ß-lactamase enzyme. The photocatalyst had a high negative docking score (-5.9 kcal mol-1) due to intense interactions within the active site of the enzyme. The molecular docking study revealed that the ligand could inhibit ß-lactamase from producing its bactericidal activity.

5.
Metabolomics ; 17(6): 53, 2021 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-34061256

RESUMO

INTRODUCTION: The silver/graphitic carbon nitride (Ag/g-C3N4) composite system exerts biocidal activity against the pathogenic bacterium Escherichia coli 1337-H that is stronger than that of well-known silver and titanium oxide (TiO2)-based composites. However, whether the Ag/g-C3N4 composite system has biocidal properties that the parent components do or do not have as separate chemical entities and whether they differ from those in Ag/TiO2 composite photocatalysts have not been clarified. OBJECTIVE: We investigated the chemical (cooperative charge handling and electronic properties) and biological (metabolic) effects exerted by the addition of Ag to g-C3N4 and to TiO2. METHODS: In this work, we undertook metabolome-wide analysis by liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry to compare the metabolite profiles of untreated E. coli 1337-H cells or those subjected to disinfection with Ag, g-C3N4, 2Ag/g-C3N4, TiO2 and 2Ag/TiO2. RESULTS: While Ag or g-C3N4 moderately affected microbial metabolism according to the mean of the altered metabolites, multiple cell systems contributing to rapid cell death were immediately affected by the light-triggered radical species produced when Ag and g-C3N4 were as xAg/g-C3N4. The effects include drastically reduced production of small metabolites essential for detoxifying reactive oxygen species and those that regulate DNA replication fidelity, cell morphology and energy status. These biological consequences were different from those caused by Ag/TiO2-based biocides, demonstrating the uniqueness of the Ag/g-C3N4 system. CONCLUSIONS: Our results support the idea that the unique Ag/g-C3N4 biocidal properties are based on synergistic action and reveal new directions for designing future photocatalysts for use in disinfection and microbial control.


Assuntos
Escherichia coli , Prata , Catálise , Luz , Metabolômica , Prata/farmacologia
6.
Molecules ; 25(17)2020 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-32887383

RESUMO

Photo-catalysis is a research field with broad applications in terms of potential technological applications related to energy production and managing, environmental protection, and chemical synthesis fields. A global goal, common to all of these fields, is to generate photo-catalytic materials able to use a renewable energy source such as the sun. As most active photocatalysts such as titanium oxides are essentially UV absorbers, they need to be upgraded in order to achieve the fruitful use of the whole solar spectrum, from UV to infrared wavelengths. A lot of different strategies have been pursued to reach this goal. Here, we selected representative examples of the most successful ones. We mainly highlighted doping and composite systems as those with higher potential in this quest. For each of these two approaches, we highlight the different possibilities explored in the literature. For doping of the main photocatalysts, we consider the use of metal and non-metals oriented to modify the band gap energy as well as to create specific localized electronic states. We also described selected cases of using up-conversion doping cations. For composite systems, we described the use of binary and ternary systems. In addition to a main photo-catalyst, these systems contain low band gap, up-conversion or plasmonic semiconductors, plasmonic and non-plasmonic metals and polymers.


Assuntos
Luz Solar , Titânio/química , Catálise/efeitos da radiação , Cinética , Temperatura , Fatores de Tempo
7.
Top Curr Chem (Cham) ; 377(5): 24, 2019 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-31468239

RESUMO

The article provides an overview of the most relevant characterization results of heterogeneous photo-catalytic materials available in the literature. First, we present a summary of the ex situ utilization of physico-chemical characterization techniques. In the majority of current works, pre and post-reaction samples are subjected to ex situ analysis using a multitechnique approach which attempts to render information about the morphological, structural, and electronic properties of relevance to interpret photoactivity. Details of the effects on physico-chemical observables of the nanostructure and the complex chemical nature (considering mono and multiphase materials with presence of several chemical elements) of typical photo-catalysts will be analyzed. Modern studies however emphasize the use of in situ tools in order to establish activity-structure links. To this end, the first point to pay attention to is to consider carefully the interaction between light and matter at the reaction cell where the characterization is carried out. Operando and spectro-kinetic methodologies will be reviewed as they would render valuable and trusting results and thus will pave the way for the future developments in photocatalysis.


Assuntos
Nanoestruturas/química , Catálise , Cinética , Processos Fotoquímicos
8.
Chem Soc Rev ; 48(2): 637-682, 2019 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-30516217

RESUMO

The combination of kinetic and spectroscopic tools has become a key scientific methodology for the understanding of catalytic behavior but its application in photocatalysis has inherent difficulties due to the nature of the energy source of the reaction. This review article provides an overview of its use by, first, presenting mechanistically derived kinetic formulations and spectroscopic data handling methods including intrinsic expressions for light and, second, highlighting representative examples of application. To do it we consider universal catalytic systems, particularly (although not exclusively) titania-based materials, and the most frequent hole and/or electron triggered reaction schemes. This review also provides a general framework to pave the way for the future progress of the spectro-kinetic approach in the photocatalysis area.

9.
Angew Chem Int Ed Engl ; 57(5): 1199-1203, 2018 01 26.
Artigo em Inglês | MEDLINE | ID: mdl-29265669

RESUMO

Understanding how a photocatalyst modulates its oxidation state, size, and structure during a photocatalytic reaction under operando conditions is strongly limited by the mismatch between (catalyst) volume sampled by light and, to date, the physicochemical techniques and probes employed to study them. A synchrotron micro-beam X-ray absorption spectroscopy study together with the computational simulation and analysis (at the X-ray cell) of the light-matter interaction occurring in powdered TiO2 -based monometallic Cu, Ni and bimetallic CuNi catalysts for hydrogen production from renewables was carried out. The combined information unveils an unexpected key catalytic role involving the phase contact between the reduced and oxidized non-noble metal phases in all catalysts and, additionally, reveals the source of the synergistic Cu-Ni interaction in the bimetallic material. The experimental method is applicable to operando studies of a wide variety of photocatalytic materials.

10.
ACS Appl Mater Interfaces ; 8(22): 13934-45, 2016 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-27203735

RESUMO

The enhancement of active triggered by surface deposition of Cu, Bi, and Ce containing oxidic species onto a high surface area anatase is analyzed through the calculation of the quantum efficiency for toluene photodegradation under UV and Sunlight-type illumination. To this end, series of Cu, Bi, and Ce containing oxides supported on anatase were synthesized having a growing content of the Cu, Bi, and Ce surface species and characterized with X-ray diffraction and photoelectron, UV-visible, and photoluminescence spectroscopies as well as transmission electron microscopy. Utilizing the surface concentration of Cu, Bi, and Ce species as a tool, we analyzed the influence of the system physicochemical properties affecting quantum efficiency in anatase-based materials. First, employing small surface concentrations of the Cu, Bi, and Ce species deposited onto (the unperturbed) anatase, we provided evidence that all steps of the photocatalytic event, including light absorption, charge recombination, as well as surface interaction with the pollutant and chemical output as to activity and selectivity have significance in the quantitative assessment of the enhancement of the efficiency parameter. Second, we analyzed samples rendering maximum quantum efficiency within all these series of materials. The study indicates that maximum enhancement over anatase displays a magnitude strongly dependent on the efficiency level of calculation and would thus require the use of the most accurate one, and that it occurs through a balance between optoelectronic and chemical properties of the composite materials. The (Cu, Bi, Ce) oxide-anatase interface plays a major role modulating the optoelectronic properties of the solids and thus the efficiency observable.

11.
ACS Appl Mater Interfaces ; 8(4): 2617-27, 2016 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-26714203

RESUMO

Metallic silver (ranging from 1 to 10 wt %) was deposited onto a graphite-like carbon nitride photocatalyst through a microemultion method. Surface, morphological, and structural properties of the resulting materials were characterized using BET and porosity measurements, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and UV-vis and photoluminescence spectroscopy. The activity of the composite samples under sunlight-type and visible illumination was measured for toluene photodegradation and was analyzed by means of the reaction rate and the quantum efficiency parameter. To obtain the latter observable, the lamp emission properties as well as the radiation field interaction with the catalyst inside the reactor were modeled and numerically calculated. The stability of the samples under both illumination conditions was also studied. The results evidence that the composite samples containing 1-10 silver wt % outperform carbon nitride for sunlight-type and visible illumination, but the optimal use of the charge generated after light absorption is obtained for the sample with 1 wt % of silver acording to the quantum efficiency calculation. The study shows that the optimum silver-g-C3N4 contact is able to outperform TiO2 reference systems (nano-TiO2 and P25) under sunlight illumination and points out that this occurs as a direct consequence of the charge handling through the interface between catalyst components. This indicates that composite systems based on g-C3N4 can be competitive in sunlight-triggered photodegradation processes to eliminate tough polluctants such as toluene, rendering active and stable systems.

12.
Phys Chem Chem Phys ; 16(36): 19540-9, 2014 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-25105950

RESUMO

Composite TiO2-WO3 oxide materials were prepared by a single pot microemulsion method and studied during calcination treatments under dry air in order to analyze the influence of tungsten on the behavior of the dominant titania component. To this end, the surface and bulk morphological and structural evolution of the solid precursors was studied using X-ray diffraction and infrared spectroscopy. In the calcination process, differences in the dominant titania component behavior appeared as a function of the W/Ti atomic ratio of the precursor. First, the crystallization of the anatase phase is affected by tungsten through an effect on the primary particle size growth. Furthermore, such an effect also influences the anatase to rutile phase transformation. The study provides evidence that the W-Ti interaction develops differently for a low/high W/Ti atomic ratio below/above 0.25 affecting fundamentally the above-mentioned anatase primary particle size growth process and the subsequent formation of the rutile phase and showing that addition of tungsten provides a way to control morphology and phase behavior in anatase-based oxide complex materials.

13.
Sci Rep ; 4: 4134, 2014 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-24549289

RESUMO

Titania (TiO2)-based nanocomposites subjected to light excitation are remarkably effective in eliciting microbial death. However, the mechanism by which these materials induce microbial death and the effects that they have on microbes are poorly understood. Here, we assess the low dose radical-mediated TiO2 photocatalytic action of such nanocomposites and evaluate the genome/proteome-wide expression profiles of Pseudomonas aeruginosa PAO1 cells after two minutes of intervention. The results indicate that the impact on the gene-wide flux distribution and metabolism is moderate in the analysed time span. Rather, the photocatalytic action triggers the decreased expression of a large array of genes/proteins specific for regulatory, signalling and growth functions in parallel with subsequent selective effects on ion homeostasis, coenzyme-independent respiration and cell wall structure. The present work provides the first solid foundation for the biocidal action of titania and may have an impact on the design of highly active photobiocidal nanomaterials.


Assuntos
Anti-Infecciosos/farmacologia , Nanocompostos/toxicidade , Pseudomonas aeruginosa/efeitos dos fármacos , Titânio/química , Anti-Infecciosos/química , Proteínas de Bactérias/metabolismo , Catálise , Espectroscopia de Ressonância de Spin Eletrônica , Nanocompostos/química , Nanocompostos/ultraestrutura , Proteômica , Pseudomonas aeruginosa/metabolismo , Pseudomonas aeruginosa/efeitos da radiação , Transcriptoma/efeitos dos fármacos , Transcriptoma/efeitos da radiação , Raios Ultravioleta
14.
Int J Mol Sci ; 14(5): 9249-66, 2013 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-23629663

RESUMO

Nanocomposites obtained from the incorporation of synthesized TiO2 nanoparticles (≈10 nm average primary particle size) in different amounts, ranging from 0.5 to 5 wt.%, into a biodegradable polycaprolactone matrix are achieved via a straightforward and commercial melting processing. The resulting nanocomposites have been structurally and thermally characterized by transmission electron microscopy (TEM), wide/small angle X-ray diffraction (WAXS/SAXS, respectively) and differential scanning calorimetry (DSC). TEM evaluation provides evidence of an excellent nanometric dispersion of the oxide component in the polymeric matrix, with aggregates having an average size well below 100 nm. Presence of these TiO2 nanoparticles induces a nucleant effect during polymer crystallization. Moreover, the antimicrobial activity of nanocomposites has been tested using both UV and visible light against Gram-negative Escherichia coli bacteria and Gram-positive Staphylococcus aureus. The bactericidal behavior has been explained through the analysis of the material optical properties, with a key role played by the creation of new electronic states within the polymer-based nanocomposites.


Assuntos
Anti-Infecciosos/síntese química , Anti-Infecciosos/farmacologia , Nanocompostos/química , Poliésteres/síntese química , Poliésteres/farmacologia , Titânio/farmacologia , Biodegradação Ambiental/efeitos dos fármacos , Varredura Diferencial de Calorimetria , Testes de Sensibilidade Microbiana , Viabilidade Microbiana/efeitos dos fármacos , Nanocompostos/ultraestrutura , Transição de Fase , Espalhamento a Baixo Ângulo , Espectrofotometria Ultravioleta , Temperatura , Termogravimetria , Difração de Raios X
15.
Phys Chem Chem Phys ; 15(22): 8640-7, 2013 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-23552520

RESUMO

The behaviour of the Pd phase in three way catalysts (TWCs) having a Ce-Zr oxide as a promoter component has been examined under CO/NO cycling conditions. In order to extract information on the role of the noble metal and the metal-promoter interface, two catalysts in, respectively, the presence or the absence of the promoter and having a similar Pd particle size were analyzed by a synchronous multitechnique approach using X-ray absorption (XAS) or high energy X-ray diffraction (HXRD) in combination with diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) and mass spectrometry (MS). From a structural point of view it is shown that the promoter oxide strongly influences Pd behaviour, limiting morphological (size/shape) and structural (formation of carbide/oxide phases) modifications occurring under dynamic conditions in the absence of the promoter. Activity measurements show that these phenomena have important chemical consequences in terms of CO/NO pollutant metal coverage(s), the occurrence of NO and/or CO dissociation steps as well as the subsequent transformation of the pollutants into CO2 and N2.


Assuntos
Monóxido de Carbono/química , Césio/química , Óxido Nítrico/química , Paládio/química , Termodinâmica , Zircônio/química , Estrutura Molecular
17.
18.
J Am Chem Soc ; 133(12): 4484-9, 2011 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-21370924

RESUMO

A combination of time-resolved X-ray absorption spectroscopy (XAS), hard X-ray diffraction (HXRD), diffuse reflectance infrared spectroscopy (DRIFTS), and mass spectrometry (MS) reveals a series of size-dependent phenomena at Pd nanoparticles upon CO/(NO+O(2)) cycling conditions. The multitechnique approach and analysis show that such size-dependent phenomena are critical for understanding Pd CO elimination behavior and, particularly, that different Pd(I) and Pd(0) centers act as active species for a size estimated by XAS to be, respectively, below and above ca. 3 nm. The relative catalytic performance of these two noble metal species indicates the intrinsic higher activity of the Pd(I) species.


Assuntos
Monóxido de Carbono/química , Nanopartículas Metálicas/química , Paládio/química , Catálise , Tamanho da Partícula
20.
J Am Chem Soc ; 132(13): 4540-1, 2010 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-20225873

RESUMO

A novel combination of time-resolved hard X-ray diffraction, diffuse reflectance infrared spectroscopy, and mass spectrometry reveals how Pd nanoparticles dissociate CO and store atomic carbon and how this carbon storage dynamically changes the population of linear and bridging CO species at the surface of the Pd nanoparticles.


Assuntos
Monóxido de Carbono/química , Carbono/química , Nanopartículas Metálicas/química , Óxido Nítrico/química , Paládio/química , Difusão , Espectrofotometria Infravermelho , Fatores de Tempo , Difração de Raios X
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