Time resolved structural dynamics of butadiyne-linked porphyrin dimers

In this work the timescales and mechanisms associated with the structural dynamics of butadiyne-linked porphyrin dimers are investigated through time resolved narrowband pump / broadband probe transient absorption spectroscopy. Our results confirm previous findings that the broadening is partly due to a distribution of structures with different (dihedral) angular conformations. Comparison of measurements with excitations on the red and blue sides of the Q-band unravel the ground and excited state conformational re-equilibration timescales. Further comparison to a planarized dimer, through addition of a ligand, provide conclusive evidence for the twisting motion performed by the porphyrin dimer in solution

Análise da influência da morfologia porosa de implantes de titânio no processo de crescimento ósseo

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-graduação em Ciências e Engenharia de Materiais, Florianópolis, 2013.O tecido ósseo está sempre suscetível a lesões, causadas por agentes externos ou patologias, onde em alguns casos a intervenção cirúrgica para instalação de implantes se faz necessária. Dentre os biomateriais utilizados como sustentação para a regeneração óssea, os implantes porosos processados a base de titânio apresentam uma combinação de fatores que viabilizam o seu emprego, entre eles, apropriadas propriedades químicas e mecânicas. Além da biocompatibilidade, a caracterização estrutural desses materiais é de relevante importância, pois suas características morfológicas também influenciam o processo de regeneração óssea. Este projeto tem como objetivo principal a caracterização de dois grupos de implantes de titânio com morfologias porosas distintas, além da avaliação do crescimento ósseo em suas fases porosas, uma vez que as amostras foram implantadas em tecidos ósseos de coelhos. As análises estruturais e de quantificação óssea foram realizadas por meio da análise de imagens tridimensionais adquiridas com a microtomografia de raios X. As amostras foram processadas por meio da técnica da metalurgia do pó, usando Titânio puro grau 1 como matéria prima e bicarbonato de amônio como agente gerador de poros. Diferentes granulometrias e proporções dos pós utilizados asseguraram diferenças morfológicas entre os dois grupos de implantes. As amostras foram implantadas em tíbias de coelhos, onde os períodos de permanência no tecido ósseo de 7, 14, 21, 28 e 35 dias foram respeitados para a avaliação do processo osseointegrativo. Foram analisados os parâmetros estruturais de porosidade, tamanho de poros e conexões, número de coordenação, permeabilidade, área superficial e grau de esfericidade dos poros de cada grupo. As correlações investigadas entre a fração de poros ocupada por osso e os parâmetros físicos indicaram a influência da morfologia porosa no processo de reparação óssea. Os resultados encontrados contribuirão para a otimização de biomateriais porosos direcionando o seu processamento para atingir propriedades que melhorem o desempenho dos implantes Bone tissue is susceptible to injuries induced by pathologies or accidents. In some cases, a surgical intervention to implant devices is necessary. Biomaterials are often used as scaffolds to bone recuperation. To be applied as a scaffold, porous titanium implants are a good choice due to their chemical and mechanical properties. Besides the biocompatibility, biomaterial implants must to offer other structural parameters which permit the bone ingrowth process. In this work, two groups of porous titanium implants were processed by powder metallurgy with distinct pore morphology. Pure titanium and ammonium bicarbonate (as pore former) were used in the samples processing. Different quantities and grain sizes of the powders provided different pore morphology for the groups. The implants were introduced into rabbits bone tissues for 7, 14, 21, 28 and 35 days. Therefore, the aim of this work is to characterize the pore phase of the titanium porous implants, and also to quantify the pore fraction occupied by neo-bone formation. The measurements were accomplished by means of X-ray microtomography image analysis. Structural parameters such as porosity, pore size, throat size, interconnectivity, permeability, surface area and pore sphericity were analyzed. The correlations between bone neoformation data and structural parameters indicate the influence of the pore shape on osseointegration process. The results of this work can be useful to improve the porous biomaterial processing

A pore-scale investigation of the effect of nanoparticle injection on properties of sandy porous media

Nanoremediation is a new groundwater remediation technology in which nanoparticles (NPs) are injected into the sub-surface to promote in-situ degradation of aquifer contaminants. Although nanoremediation is an effective process to eliminate contaminants in-situ, its success relies on sufficiently mobile NPs that can reach the contaminated zones and remain there to facilitate chemical degradation of contaminants. Therefore, understanding the main parameters that control the mobility and retention of NPs in saturated porous media is a key component of designing a successful nanoremediation process. This work presents the outcome of a pore-scale study of nZVI NP (zero-valent iron) transport in sandy porous media using the non-destructive 3D imaging technique, X-ray computed micro-tomography (X-ray micro-CT). We investigate the effect of grain size (fine, coarse, carbonate and mixed sand) and composition (carbonate vs sand grains) on the mobility and retention of NPs in sand columns. To achieve this, we used four columns packed with grains of different sizes and compositions. The main contribution of this work is, therefore, to understand the effect of NP injection on the structural and geometric properties of sandy porous media and to identify the main pore-scale mechanisms controlling NP transport and entrapment. Our experiment shows that the pore geometries change because of NP injection. Pore clogging is evidenced through pore size and throat size distribution displaying a shift to the left with a noticeable reduction in pore connectivity in all the columns. The porosity and permeability of the columns studied display significant reduction as result of the NP injection

Plasmonic catalysis with designer nanoparticles

Catalysis is central to a more sustainable future and a circular economy. If the energy required to drive catalytic processes could be harvested directly from sunlight, the possibility of replacing contemporary processes based on terrestrial fuels by the conversion of light into chemical energy could become a step closer to reality. Plasmonic catalysis is currently at the forefront of photocatalysis, enabling one to overcome the limitations of "classical" wide bandgap semiconductors for solar-driven chemistry. Plasmonic catalysis enables the acceleration and control of a variety of molecular transformations due to the localized surface plasmon resonance (LSPR) excitation. Studies in this area have often focused on the fundamental understanding of plasmonic catalysis and the demonstration of plasmonic catalytic activities towards different reactions. In this feature article, we discuss recent contributions from our group in this field by employing plasmonic nanoparticles (NPs) with controllable features as model systems to gain insights into structure-performance relationships in plasmonic catalysis. We start by discussing the effect of size, shape, and composition in plasmonic NPs over their activities towards LSPR-mediated molecular transformations. Then, we focus on the effect of metal support interactions over activities, reaction selectivity, and reaction pathways. Next, we shift to the control over the structure in hollow NPs and nanorattles. Inspired by the findings from these model systems, we demonstrate a design-driven strategy for the development of plasmonic catalysts based on plasmonic-catalytic multicomponent NPs for two types of molecular transformations: the selective hydrogenation of phenylacetylene and the oxygen evolution reaction. Finally, future directions, challenges, and perspectives in the field of plasmonic catalysis with designer NPs are discussed. We believe that the examples and concepts presented herein may inspire work and progress in plasmonic catalysis encompassing the design of plasmonic multicomponent materials, new strategies to control reaction selectivity, and the unraveling of stability and reaction mechanisms.Peer reviewe

A Review of Testbeds on SCADA Systems with Malware Analysis

Supervisory control and data acquisition (SCADA) systems are among the major types of Industrial Control Systems (ICS) and are responsible for monitoring and controlling essential infrastructures such as power generation, water treatment, and transportation. Very common and with high added-value, these systems have malware as one of their main threats, and due to their characteristics, it is practically impossible to test the security of a system without compromising it, requiring simulated test platforms to verify their cyber resilience. This review will discuss the most recent studies on ICS testbeds with a focus on cybersecurity and malware impact analysis

PHOTOCHEMICAL REDUCTION OF CR(VI) FROM ELECTROPLATING WASTEWATER USING INDUSTRIAL STEEL WASTE AS IRON SOURCE

The use of chromium in different industrial activities, such as electroplating, textile dyeing, leather tanning and metallurgy, results in toxic wastewaters containing chromium species, which must be treated before discharging into receiving waters. In this work, an industrial steel waste (mill scale found on all hot-rolled steel products) was evaluated as iron source to promote the reduction of hexavalent chromium species present in an electroplating wastewater. Mill scale (MS) was characterized by spontaneous magnetization, point of zero charge (pHpzc) and metal leaching. The efficiency of MS was studied in the presence and absence of reducing agents (citric acid and oxalic acid), and its stability and the influence of the homogeneous reaction on the overall efficiency was also evaluated using a batch system. Higher concentrations of MS resulted in an increase in the rate of Cr (VI) reduction. It was observed a negligible effect of citric acid and oxalic acid on Cr(VI) reduction in the absence of MS, however, in the presence of MS particles and organic acids, Cr(VI) reduction is significantly enhanced. It was verified that MS acts only as source of iron for the solution. The results indicate that MS can be used effectively in wastewater treatment, more precisely in Cr (VI) reduction