MoS2 and MoS2 Nanocomposites for Adsorption and Photodegradation of Water Pollutants: A Review

The need for fresh and conveniently treated water has become a major concern in recent years. Molybdenum disulfide (MoS2) nanomaterials are attracting attention in various fields, such as energy, hydrogen production, and water decontamination. This review provides an overview of the recent developments in MoS2-based nanomaterials for water treatment via adsorption and photodegradation. Primary attention is given to the structure, properties, and major methods for the synthesis and modification of MoS2, aiming for efficient water-contaminant removal. The combination of MoS2 with other components results in nanocomposites that can be separated easily or that present enhanced adsorptive and photocatalytic properties. The performance of these materials in the adsorption of heavy metal ions and organic contaminants, such as dyes and drugs, is reviewed. The review also summarizes current progress in the photocatalytic degradation of various water pollutants, using MoS2-based nanomaterials under UV-VIS light irradiation. MoS2-based materials showed good activity after several reuse cycles and in real water scenarios. Regarding the ecotoxicity of the MoS2, the number of studies is still limited, and more work is needed to effectively evaluate the risks of using this nanomaterial in water treatment.publishe

Eficácia de barreiras acústicas

O tráfego rodoviário tem impactes significativos no ambiente, na saúde e na qualidade de vida das populações. Os avultados investimentos aplicados na construção de barreiras acústicas nem sempre se traduzem numa redução eficaz do ruído. Esta comunicação apresenta os resultados da avaliação da eficácia de três barreiras acústicas colocadas em vias de comunicação com volumes de tráfego distintos. Os materiais que as constituem são blocos de betão parcialmente preenchidos com lã de rocha, chapa metálica perfurada com lã de rocha e painéis pré-fabricados de betão com inertes leves. A avaliação da eficácia de cada barreira acústica foi efectuada com recurso a sonómetros colocados à frente, no tardoz e numa zona contígua não influenciada pela mesma. Para complementar a avaliação, estabelecem-se comparações entre os valores medidos e os valores obtidos a partir de modelos simplificados de comportamento.The road traffic has significant impacts in the environment, in population quality of life and health. The large investments applied in construction of acoustics barriers nor always result in an efficient noise reduction. This paper presents the results of the evaluation of the effectiveness of three acoustics barriers placed in highways with distinct traffic. The materials that constitute the barriers are concrete blocks partially filled with rockwool, perforated metallic shell with rockwool and prefabricated concrete panels. The evaluation of the effectiveness of each acoustics barrier was carried out with sound level meters placed in the front, behind and in a contiguous zone not influenced by the barrier. Comparisons between the measured values and the values gotten from simplified behaviour models are established

Descolagem de um revestimento cerâmico em fachada

A capacidade de um revestimento cerâmico resistir à descolagem depende da correcta selecção do produto de colagem e do método de colagem. Estes devem ser adequados à intensidade das acções previstas, ao tipo de utilização do revestimento, às características do suporte e ao tipo de revestimento. Uma cuidada concepção do revestimento e a selecção do produto de colagem adequado para cada situação não garante por si só a eficiência da colagem sendo necessário que essas precauções sejam acompanhadas de uma correcta execução. Nesta comunicação apresenta-se um trabalho onde se procedeu à análise das causas da des-colagem de um revestimento cerâmico de uma fachada. Procede-se à caracterização da situação existente e à descrição dos ensaios realizados. Propõem-se soluções de reabilitação e elaboram-se recomendações de aplicação

Estudo de um edifício de habitação multifamiliar com anomalias não estruturais

Os erros de construção grosseiros, a reduzida qualidade de execução, o deficiente acompanhamento/fiscalização dos trabalhos em obra, o completo desrespeito da legislação em vigor desde a fase de projecto não são invulgares. Estas situações provocam elevados prejuízos materiais, reduzem a qualidade de vida das populações e chegam por vezes a constituir risco para a vida. Nesta comunicação, apresenta-se um trabalho onde se procedeu ao levantamento das patologias de um edifício de habitação com alguns dos vícios anteriormente referidos. Realizaram-se várias visitas ao local, procedeu-se ao registo das anomalias, analisou-se o projecto de licenciamento e recolheu-se o testemunho de moradores. Fez-se uma análise das causas das patologias encontradas e propõem-se medidas correctivas

Drug Delivery Systems and Flavonoids: Current Knowledge in Melanoma Treatment and Future Perspectives

Melanoma is an aggressive form of skin cancer with a high prevalence in the population. An early diagnosis is crucial to cure this disease. Still, when this is not possible, combining potent pharmacological agents and effective drug delivery systems is essential to achieve optimal treatment and improve patients' quality of life. Nanotechnology application in biomedical sciences to encapsulate anticancer drugs, including flavonoids, in order to enhance therapeutic efficacy has attracted particular interest. Flavonoids have shown effectiveness against various types of cancers including in melanoma, but they show low aqueous solubility, low stability and very poor oral bioavailability. The utilization of novel drug delivery systems could increase flavonoid bioavailability, thereby potentiating its antitumor effects in melanoma. This review summarizes the potential of different flavonoids in melanoma treatment and the several nanosystems used to improve their biological activity, considering published information that reported improved biological and pharmacological properties of encapsulated flavonoids.publishe

Towards efficient ciprofloxacin adsorption using magnetic hybrid nanoparticles prepared with κ-, ι-, and λ-carrageenan

The efficient removal of the antibiotic ciprofloxacin (CIP) from aqueous samples using magnetic nanosorbents prepared using three sulfated polysaccharides, κ-, ι- and λ-carrageenan and an alkoxysilane agent containing a reactive epoxide ring is described. The prepared nanosorbents were characterized in detail using FTIR spectroscopy, solid-state 29Si and 13C NMR spectroscopy and elemental microanalysis. The synthesis method was more effective for incorporating higher amounts of κ-carrageenan in the siliceous shells. Although being less sulfated, κ-carrageenan is cheaper than the other carrageenan tested. The CIP adsorption was a cooperative process, well described by the Dubinin–Radushkevich isotherm, with maximum adsorption capacities of 878, 969 and 865 mg/g for κ-, ι- and λ-carrageenan sorbents, respectively. Overall, the produced magnetic nanosorbents are among the best magnetic systems with high adsorptive efficiency for CIP. It is suggested that protonated CIP molecules are exchanged with ester sulfate counterions of carrageenan at the particles’ surface as the main pathway for CIP adsorption. The adsorption process was exothermic and entropically favorable for the three sorbents. However, at 298 K, the adsorption was spontaneous for κ-carrageenan-based sorbents and non-spontaneous for ι- and λ-carrageenan particles. The magnetic sorbents could be reused and maintained their ability towards CIP removal up to four cycles. The removal efficiency in wastewater was enhanced with the sorbent dose. Graphical abstract: [Figure not available: see fulltext.] Magnetic carrageenan nanosorbents were prepared using three carrageenan polysaccharides (κ-, ι-, and λ-carrageenan). The resulting magnetic particles removed the antibiotic ciprofloxacin efficiently from ultra-pure water and wastewater samples. Magnetic features enabled the fast magnetic separation of the nanosorbents from water.publishe

An integrated approach for trace detection of pollutants in water using polyelectrolyte functionalized magneto-plasmonic nanosorbents

Resistance of pathogenic micro-organisms to conventional antibiotics is an essential issue for public health. The presence of such pharmaceuticals in aquatic ecosystems has been of major concern for which remediation and ultra-sensitive monitoring methods have been proposed. A less explored strategy involves the application of multifunctional nanosorbents for the uptake and subsequent detection of vestigial contaminants. In this study, colloidal nanoparticles (NPs) of iron oxide and gold were encapsulated in multi-layers of a charged polyelectrolyte (PEI: polyethyleneimine), envisaging the effective capture of tetracycline (TC) and its subsequent detection by Surface Enhanced Raman Scattering (SERS). Adsorption studies were performed by varying operational parameters, such as the solution pH and contact time, in order to evaluate the performance of the nanosorbents for the uptake of TC from water. While the magnetic nanosorbents with an external PEI layer (Fe3O4@PEI and Fe3O4@PEI-Au@PEI particles) have shown better uptake efficiency for TC, these materials showed less SERS sensitivity than the Fe3O4@PEI- Au nanosorbents, whose SERS sensitivity for TC in water has reached the limit of detection of 10 nM. Thus, this study highlights the potential of such magneto-plasmonic nanosorbents as multi-functional platforms for targeting specific contaminants in water, by taking into consideration both functionalities investigated: the removal by adsorption and the SERS detection across the nanosorbents' surfaces.publishe

Highly indistinguishable single photons from incoherently and coherently excited GaAs quantum dots

Semiconductor quantum dots are converging towards the demanding requirements of photonic quantum technologies. Among different systems, quantum dots with dimensions exceeding the free-exciton Bohr radius are appealing because of their high oscillator strengths. While this property has received much attention in the context of cavity quantum electrodynamics, little is known about the degree of indistinguishability of single photons consecutively emitted by such dots and on the proper excitation schemes to achieve high indistinguishability. A prominent example is represented by GaAs quantum dots obtained by local droplet etching, which recently outperformed other systems as triggered sources of entangled photon pairs. On these dots, we compare different single-photon excitation mechanisms, and we find (i) a "phonon bottleneck" and poor indistinguishability for conventional excitation via excited states and (ii) photon indistinguishablilities above 90% for both strictly resonant and for incoherent acoustic- and optical-phonon-assisted excitation. Among the excitation schemes, optical phonon-assisted excitation enables straightforward laser rejection without a compromise on the source brightness together with a high photon indistinguishability

p-Sulfonic acid calixarenes as efficient and reusable organocatalysts for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones/-thiones

AbstractA new and efficient methodology is proposed for obtaining 3,4-dihydropyrimidin-2(1H)-ones/-thiones through Biginelli reactions. It is based on the use of less than the stoichiometric amount of p-sulfonic acid calixarenes as organocatalysts. A number of aromatic aldehydes as well as urea or thiourea can be employed for successfully synthesizing the corresponding Biginelli adducts. The described methodology is devoid of metal-containing catalysts, which in turn is very attractive for safely producing 3,4-dihydropyrimidin-2-(1H)-ones/-thiones of pharmacological interest. In addition, the catalyst efficiency is not compromised after its successive use in reactions. This is the first report about the application of calixarenes as catalysts in the multicomponent Biginelli reaction