Hummers’ and Brodie’s graphene oxides as photocatalysts for phenol degradation

Undoped metal-free graphene oxide (GO) materials prepared by either a modified Hummers’ (GO-H) or a Brodie’s (GO-B) method were tested as photocatalysts in aqueous solution for the oxidative conversion of phenol. In the dark, the adsorptive capacity of GO-B towards phenol (~35%) was higher than that of GO-H (~15%). Upon near-UV/Vis irradiation, GO-H was able to remove 21% of phenol after 180 min, mostly through adsorption. On the other hand, by using less energetic visible irradiation, GO-B removed as much as 95% in just 90 min. By thorough characterization of the prepared materials (SEM, HRTEM, TGA, TPD, Raman, XRD, XPS and photoluminescence) the observed performances could be explained in terms of their different surface chemistries. The GO-B presents the lower concentration of oxygen functional groups (in particular carbonyl groups as revealed by XPS) and it has a considerably higher photocatalytic activity compared to GO-H. Photoluminescence (PL) of liquid dispersions and XRD analysis of powders showed lower PL intensity and smaller interlayer distance for GO-B relative to GO-H, respectively: this suggests lower electron-hole recombination and enhanced electron transfer in GO-B, in support of its boosted photocatalytic activity. Reusability tests showed no efficiency loss after a second usage cycle and over three runs under visible irradiation, which was in line with the similarity of the XPS spectra of the fresh and used GO-B materials. Moreover, scavenging studies revealed that holes and hydroxyl radicals were the main reactive species in play during the photocatalytic process. The obtained results, establish for the first time, that GO prepared by Brodie’s method is an active and stable undoped metal-free photocatalyst for phenol degradation in aqueous solutions, opening new paths for the application of more sustainable and metal-free materials for water treatment solutions.This work was financially supported by project NORTE-01- 0145-FEDER-031049 (InSpeCt) funded by FEDER funds through NORTE 2020 - Programa Operacional Regional do NORTE and by national funds (PIDDAC) through FCT/MCTES (PTDC/EAMAMB/ 31049/2017). We would also like to thank the scientific collaboration under project ‘‘AIProcMat@N2020 - Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020” (NORTE-01-0145-FEDER-000006, NORTE 2020, Portugal 2020 Partnership Agreement, through FEDER), project ‘‘Associate Laboratory LSRE-LCM” (UID/EQU/50020/2019 - FCT/ MCTES – PIDDAC) and project 2DMAT4FUEL (POCI-01-0145- FEDER-029600 - COMPETE2020 – FCT/MCTES - PIDDAC). MP acknowledges the PhD research grant from FCT (Ref. SFRH/ BD/102086/2014). LMPM acknowledges the Spanish Ministry of Economy and Competitiveness (MINECO) and the European Social Fund for a Ramon y Cajal research contract (RYC-2016-19347). GD acknowledges the Slovenian Research Agency (P2-0393). PF acknowledges support from Prince Sultan Bin Abdulaziz International Prize for Water–Alternative Water Resources Prize 201

Una nueva identidad para los farmacéuticos : la Sociedad Farmacéutica Mexicana en el cambio de siglo (1890-1919)

La Sociedad Farmacéutica Mexicana fue fundada en 1871. En su interior los farmacéuticos se organizaron y apoyaron las tareas necesarias para el desarrollo de su profesión : elaborar una farmacopea, velar por los intereses y el mejoramiento de la profesión, y reunir las leyes relativas al ejercicio de la farmacia. La Sociedad desempeñó un importante papel en el proceso de institucionalización de la farmacia y en la conquista de nuevos espacios, particularmente en lo referente al traslado de la carrera de farmacia de la Escuela Nacional de Medicina a la Facultad de Ciencias Químicas en 1919. En este establecimiento los farmacéuticos asumieron una nueva identidad como químicos

Nanotubos e grafeno: os primos mais jovens na família do carbono!

O carbono é o sexto elemento mais abundante do universo, encontrando-se presente tanto na forma orgânica, como em materiais inorgânicos. Além das três formas alotrópicas que ocorrem naturalmente (carbono amorfo, grafite e diamante), podem ser também sintetizadas estruturas de carbono com dimensões nanométricas. Nos últimos anos foram descobertas e caracterizadas novas e interessantes nanoestruturas de carbono, incluindo os nanotubos de carbono e o grafeno. Este breve artigo faz uma resenha sobre os métodos de síntese e caracterização destes dois materiais, aludindo a algumas das suas propriedades mais extraordinárias, bem como às suas aplicações mais recentes e de maior impacto em diversos domínios da ciência e da tecnologia, permitindo, de uma forma simples, introduzir os leitores menos familiarizados com o tema no fascinante mundo destas duas nanoestruturas de carbono

Perifollicular erythema as a trichoscopy sign of progression in frontal fibrosing alopecia

Frontal fibrosing alopecia (FFA) in an entity characterized by the recession of the frontotemporal hairline (FTHL) with alopecic scarring change. In recent years there are numerous articles discussing the usefulness of dermoscopy for the clinical diagnosis of different types of scarring alopecia

Graphene-based materials in catalytic wet peroxide oxidation

In catalytic wet peroxide oxidation (CWPO),an advanced oxidation process, hydrogen peroxide (H2O2) is decomposed catalytically giving rise to hydroxyl radicals (HO•).These radicals, exhibiting high oxidizing potential, serve as effective and non selective species for the degradation of several organic pollutants in liquid phase. Since the report of Lücking et al. [1], carbon materials have been explored as catalysts for CWPO[2]. Recent reports address process intensification issues, broadening the window of industrial applications for this wastewater treatment technology [3]. In this work, graphene-based materials were tested for the first time as catalysts for CWPO

Photocatalytic performance of palladium and carbon modified TiO2 using solar radiation

TiO2 photocatalysts were synthesized by the sol–gel method in the presence of Pd2+ ions and Tween 80. For each material, the effect of the synthesis conditions was studied by its characterization. Photoactivity was evaluated for the selective degradation of phenol (as model pollutant) with Aldrich humic acid (as usual interference) in the reaction mixture, using UV or visible lamps, and under natural sunlight. The materials were able to efficiently degrade phenol, even in the presence of humic acid in the mixture. The solar radiation experiment showed the outstanding photocatalytic activity achieved by TiO2 modified with carbon and palladium: 74 % of phenol degradation (70 % of mineralization, without Pd leaching) after 5 h of exposure.Fil: Rossi, Lucia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Villabrille, Paula Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Pastrana Martínez, L.M.. Universidad de Granada; EspañaFil: Caregnato, Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Rosso, Janina Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentin

Síntesis y evaluación citotoxica de derivados halogenados y peracetylados de nucleósidos en celulas de cancer de mama

Objectives. To make the synthesis of halogenated derivatives on the nitrogenous base and their respective acyl ester and amide type derivatives for all hydroxyl and amine groups of the uridine and cytarabine nucleosides, and evaluate cytotoxicity against breast cancer cell line. Methods. First, it was accomplished the halogenation reaction on the 5-position of the nitrogenous base, subsequently, the ester and amide derivatives were performed for all hydroxyl and amine group present in the nucleosides. Besides, the uridine acetonide derivatives as prepared by acid catalysis. The products were characterized by nuclear magnetic resonance spectroscopy (1H RMN y 13C RMN) and mass spectrometry in positive mode by direct injection. Derivatives were evaluated in Chinese hamster ovary (CHO-K1) and human breast cancer (MCF-7) cell lines. Results. The four derivatives were obtained with chlorine and bromine for the uridine and cytarabine, respectively, their respective per-acetylated derivatives, the per-acetylated nucleoside and the uridine acetonide; the compounds were obtained with efficiency over 90%. The per-acetylated nucleosides and the halogenated and per-acetylated derivatives did not show inhibitory effects on cell viability in MCF-7 cell line. However, the per-acetylated and halogenated derivatives presented a higher cytotoxic activity than their respective per-acetylated nucleoside. The uridine 3’,4’-acetonide showed a significant cytotoxicity on both cell lines. Conclusions. The per-acetylated nucleoside, and the respective halogenated derivatives with chlorine and bromine were obtained with high yields, nevertheless, these compounds did not exhibit a significant anti-proliferative activity (p˂0.05), possibly due to a low intra-cellular activation.Objetivos: Sintetizar derivados halogenados sobre la base nitrogenada, sus respectivos derivados tipo éster o amida de todos los grupos hidroxilo y amina presentes en los nucleósidos uridina y citarabina, y evaluar su actividad citotóxica sobre una línea celular de cáncer de mama. Metodología: primero se realizó la reacción de halogenación en la posición 5 de la base nitrogenada, posteriormente se formaron los ésteres y amidas de todos los grupos hidroxilos y amino presentes en los nucleósidos. Además, se preparó el derivado acetónido con catálisis ácida. Los compuestos se caracterizaron por espectroscopía de resonancia magnética nuclear (RMN 1H y RMN 13C) y espectrometría de masas por inyección directa en modo positivo. Los derivados se evaluaron sobre líneas celulares de tumor de Ovario de Hámster Chino (CHO) y de cáncer de mamá (MCF-7). Resultados: Se obtuvieron 4 derivados mono-halogenados con cloro y bromo de la uridina y citarabina, respectivamente, sus respectivos derivados per-acetilados, los nucleósidos per-acetilados y el acetónido de la uridina; los compuestos se obtuvieron con rendimientos superiores a 90%. Los nucleósidos per-acetilados, y los derivados per-acetilados y halogenados no exhibieron una inhibición significativa de la viabilidad celular en ambas líneas celulares, sin embargo, de estos, los derivados per-acetilados y halogenados presentaron mayor actividad citotóxica que los respectivos nucleósidos per-acetilados. El derivado acetónido de la uridina mostró citotoxicidad significativa sobre ambas líneas celulares. Conclusiones: se obtuvieron los nucleósidos per-acetilados y los respectivos derivados clorados y bromados de estos, con rendimientos altos, sin embargo, estos compuestos no exhibieron una actividad anti-proliferativa significativa (p˂0,05), posiblemente debido a una baja activación intra-celular de los nucleósidos

Influence of Electrostatic Interactions During the Resorcinol-Formaldehyde Polymerization on the Characteristics of Mo-Doped Carbon Gels

The resorcinol (R)-formaldehyde (F) polymerization was carried out in different experimental conditions to obtain RF/Mo doped carbon xerogels with different morphology, porosity and nature and dispersion of metal. Attractive or repulsive electrostatic interactions were forced in the starting aqueous solution of RF-monomers using different synthesis conditions, namely, combinations of cationic or anionic surfactants, Mo-precursors and pH values. The results showed that when both cationic surfactant and Mo-precursor were used at neutral pH, attractive interactions with the anionic RF-macromolecules are favored during polymerization and the final carbon xerogel exhibited the most developed porosity and the strongest Mo-organic phase interaction, leading to deeper Mo-phase reduction during carbonization and the formation of highly-dispersed crystalline nanoparticles of Mo2C. On the contrary, the use of both anionic surfactant and Mo-precursor leads to repulsive interactions, which generates less porous carbon gels with a Mo-phase formed by large MoO3 platelet structures and low Mo-surface contents. RF/Mo-doped gels with intermediate properties were obtained by combining cationic and anionic surfactants, metal precursors or both. After carbonization, the obtained materials would be suitable to be used directly as catalysts with different physicochemical properties and active phases.Spanish Project from ERDF/Ministry of Science, Innovation and Universities-State Research Agency RTI2018-099224-B-I0

Nanopartículas magnéticas como catalisadores no tratamento de águas utilizando o processo de foto-Fenton

O interesse nas aplicações de nanopartículas magnéticas tem crescido em quase todos os campos, destacando-se mais recentemente a utilização de nanopartículas de óxidos de ferro para tratamento de águas. De entre os óxidos de ferro existentes na natureza, destacam-se o a-Fe2O3, o g-Fe2O3 e o Fe3O4, que podem ser preparados laboratorialmente por métodos de co-precipitação [1], decomposição térmica [2] e síntese hidrotérmica [3]. As nanopartículas superparamagnéticas de óxido de ferro, também conhecidas como SPIONs - superparamagnetic iron oxide nanoparticles, são um caso particular devido à relação entre a distribuição de tamanhos das partículas e a carga superficial. A implementação destes materiais como catalisadores no tratamento de águas e águas residuais pode revolucionar o conceito das tecnologias catalíticas de tratamento porque quando estas nanopartículas, com propriedades magnéticas, são utilizadas em suspensão (i) proporcionam uma maior área de contacto entre a fase ativa e o meio aquoso e (ii) podem ser rapidamente (e facilmente) separadas do meio líquido por efeito de um campo magnético, ficando retidas no reator catalítico. Desta forma são ultrapassadas, tanto a principal limitação encontrada quando são utilizados catalisadores sem propriedades magnéticas em suspensão (difícil separação por processos de filtração), como a limitação associada à deposição de nanopartículas em substratos fixos (típica diminuição da atividade catalítica). Por outro lado, os compostos farmacêuticos são poluentes de maior relevância devido aos efeitos nefastos que podem causar na saúde pública, nos ecossistemas e no ambiente em geral, onde aparecem como resultado do seu consumo crescente e da sua difícil degradação em estações de tratamento de águas residuais. Estes compostos têm sido encontrados em águas subterrâneas, águas de superfície e inclusivamente em águas utilizadas para consumo, sendo esta última uma situação mais alarmante. Em particular, a difenidramina constituí o princípio ativo de diversos produtos farmacêutico, como o Benadryl®, e é classificada como anti-histamínico de primeira geração para formulações farmacêuticas utilizadas no tratamento de rinite, conjuntivite, insónia, picadas de insetos, enjoos/ansiedade, entre outros. Aparece nas águas devido à sua baixa biodegradabilidade e tem demonstrado efeitos tóxicos, cancerígenos e mutagénicos [4]. Por este motivo, no presente trabalho, foram preparados e caracterizados materiais à base de óxido de ferro com propriedades magnéticas para serem testados na degradação de difenidramina pelo processo de foto-Fenton, onde é utilizada uma mistura catalítica fortemente oxidante de um agente contendo ferro e peróxido de hidrogénio (H2O2)

Functionalized Graphene Derivatives and TiO2 for High Visible Light Photodegradation of Azo Dyes

Functionalized graphene derivatives including graphene oxide (GO), reduced graphene oxide (rGO), and heteroatom (nitrogen/sulphur (N/S) or boron (B))-doped graphene were used to synthesize composites with TiO2 (T). The photocatalytic performance of composites was assessed for the degradation of Orange G dye (OG) under simulated solar light. All the prepared graphene derivatives—TiO2 composites showed better photocatalytic performance than bare TiO2. A higher photocatalytic activity was found for the composites containing GO and N/S co-doped rGO (kapp = 109.2 × 10−3 and 48.4 × 10−3 min−1 , for GO-T and rGONS-T, respectively). The influence of both initial solution pH and the reactive species involved in the OG degradation pathway were studied. The photocatalytic activity of the samples decreased with the increase of the initial pH (from 3.0 to 10.0) due to the occurrence of electrostatic repulsive forces between the photocatalysts surface and the molecules of OG, both negatively charged. The use of selective scavengers showed that although the photogenerated holes dominate the degradation mechanism, radicals and singlet oxygen also participate in the OG degradation pathway. In addition, reutilization experiments indicated that the samples were stable under the reaction conditions used.ERDF/Ministry of Science, Innovation and Universities-State Research Agency RTI2018-099224-B-I0