Back to the basics: probing the role of surfaces in the experimentally observed morphological evolution of ZnO

Although the physics and chemistry of materials are driven by exposed surfaces in the morphology, they are fleeting, making them inherently challenging to study experimentally. The rational design of their morphology and delivery in a synthesis process remains complex because of the numerous kinetic parameters that involve the effective shocks of atoms or clusters, which end up leading to the formation of different morphologies. Herein, we combined functional density theory calculations of the surface energies of ZnO and the Wulff construction to develop a simple computational model capable of predicting its available morphologies in an attempt to guide the search for images obtained by field-emission scanning electron microscopy (FE-SEM). The figures in this morphology map agree with the experimental FE-SEM images. The mechanism of this computational model is as follows: when the model is used, a reaction pathway is designed to find a given morphology and the ideal step height in the whole morphology map in the practical experiment. This concept article provides a practical tool to understand, at the atomic level, the routes for the morphological evolution observed in experiments as well as their correlation with changes in the properties of materials based solely on theoretical calculations. The findings presented herein not only explain the occurrence of changes during the synthesis (with targeted reaction characteristics that underpin an essential structure–function relationship) but also offer deep insights into how to enhance the efficiency of other metal-oxide-based materials via matching

The hinge morphology of SnO2 as multifunctional semiconductor: What we can learn from simulations, theory, and experiments

Our interaction with materials occurs through their surfaces whose properties are strongly dependent on morphology, structure, and atomic arrangement. Unfortunately, obtaining a detailed correlation between the surface morphology with its properties is not straightforward. SnO2 is a multifunctional semiconductor ceramic that is exploited in several technological devices from sensor to energy storage, water splitting, and solar to fuel photocatalysis. This work focused on the structural, energetic, and electronic properties of low and high index surfaces of SnO2 semiconductor and assessed the morphology-dependent process via first-principles calculations, at the density functional theory level. Importantly, our explicitly dynamic approach elucidates the atomic arrangements and stability of the exposed surfaces to provide a close match between experimental field emission scanning electron microscopy images and computational simulation. These findings can potentially set a foundation for establishing synthesis techniques for drive the morphology evolution through the control of temperature/pressure, and/or based on surface interactions of the selective adsorption of solvents/surfactants.This work was supported by Generalitat Valenciana, Universitat Jaume I, and São Paulo Research Foundation (FAPESP, grant number 2013/07296-2 and 2022/08048-1). A.F.G. acknowledges the Generalitat Valenciana (Conselleria de Innovación, Universidades, Ciencia y Sociedad Digital) for the postdoctoral contract (CIAPOS/2021/106) and Universitat Jaume I for the funding though its Research Stay Grants (E-2022-05). J.A. acknowledges Universitat Jaume I (project UJI-B2019-30), and Generalitat Valenciana (Conselleria de Innovación, Universidades, Ciencia y Sociedad Digital – project CIAICO/2021/122) for financially supporting this research

Compreensão da referência espacial e comprometimento cognitivo pela Doença de Alzheimer

This research aims to examine how Brazilian Portuguese speakers understand and interpret the linguistic-visual representation of a locative scene, in which two objects are arranged in different spatial relationships. Research participants are divided into two age groups (young adults and older adults) and two levels of cognitive impairment (participants with mild to moderate cognitive impairment due to probable Alzheimer's disease and participants without cognitive impairment). To demonstrate a possible correlation between cognitive decline in the elderly group and changes in the linguistic-visual understanding of spatiality, we conducted a pilot study on the interpretation of spatial scenes, whose ambiguity can be resolved by adopting a Vantage Point over the Figure-Ground relationship and, consequently, the application of a Spatial Frame of Reference. By comparing different age groups, we intend to monitor how these two domains of cognition are preserved in the aging process and whether memory deficits affect the linguistic description of space. Our preliminary results allow us to make inferences about the costs of processing spatial information which, as expected, were considerably higher in older age and cognitive impairment groups; in addition, the scale ratings for the different response options indicate a maintenance in the type of Frame of Reference applied to resolve the spatial ambiguity. Furthermore, we found a general preference among speakers of Brazilian Portuguese for a Frame of Reference different from that adopted by other languages ​​of European origin, which we have subsequently replicated in other analyses.Esta pesquisa pretende examinar de que forma os falantes do Português Brasileiro compreendem e interpretam a representação linguístico-visual de cenas locativas, nas quais dois objetos estão dispostos em relações espaciais diferentes. Os participantes da pesquisa foram distribuídos em dois grupos etários (adultos jovens e adultos idosos) e dois níveis de comprometimento cognitivo (idosos com comprometimento cognitivo leve ou moderado devido a provável doença de Alzheimer e pessoas sem comprometimento cognitivo). Para demonstrar uma possível correlação entre o declínio cognitivo dos grupos de idosos e alterações na compreensão linguístico-visual da espacialidade, conduzimos um estudo-piloto sobre a interpretação de cenas espaciais, cuja ambiguidade pode ser resolvida pela adoção de um “Ponto de Vantagem” sobre a relação Figura-Fundo e, consequentemente pela aplicação de um “Frame de Referência” espacial. Ao comparar grupos com idades diferentes, pretendemos monitorar como estes dois domínios cognitivos estão preservados no processo de envelhecimento e verificar como os déficits provocados pela demência afetam a descrição linguística de espaço. Nossos resultados preliminares nos permitem tecer considerações a respeito dos custos de processamento das informações espaciais que, como esperado, foram consideravelmente mais altos em grupos com maior faixa etária e com comprometimento cognitivo; além da qualidade das respostas aos testes, que indicam uma manutenção no tipo de Frame aplicado para resolver a ambiguidade espacial. Além disso, como achado desta pesquisa, encontramos uma preferência geral do falante do português brasileiro por um Frame de Referência diferente daquele adotado por outras línguas de origem europeia

Growth kinetics of vanadium pentoxide nanostructures under hydrothermal conditions

The work reported here involved a study of the growth kinetics of V2O5nH2O nanostructures under hydrothermal conditions. The coarsening process of V2O5nH2O nanoribbons was followed by subjecting the as-prepared suspensions to hydrothermal treatments at 80 °C for periods ranging from 0 to 7200 min. X-ray diffraction (XRD) confirms that the hydrothermal treatments at 80 °C caused no significant modification of the long-range order structure of samples subjected to different periods of hydrothermal treatment. Field emission scanning transmission electron microscope (FE-STEM) was used to analyze the morphology and width distribution of the nanostructures. The results indicated that the crystal growth mechanism in the [1 0 0] direction of vanadium pentoxide 1D nanostructure under hydrothermal conditions is well described by the oriented attachment (OA) mechanism. This evidence was supported by HRTEM images showing the existence of defects at the interface between nanostructures, which is characteristic of the oriented attachment (OA) mechanism.FAPESPCNPqLNL

Surfactant-Mediated Morphology and Photocatalytic Activity of α‑Ag2WO4 Material

In the present work, the morphology (hexagonal rod-like vs cuboid-like) of an α-Ag2WO4 solid-state material is manipulated by a simple controlled-precipitation method, with and without the presence of the anionic surfactant sodium dodecyl sulfate (SDS), respectively, over short reaction times. Characterization techniques, such as X-ray diffraction analysis, Rietveld refinement analysis, Fourier-transform (FT) infrared spectroscopy, FT Raman spectroscopy, UV–vis spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction, energy-dispersive X-ray spectroscopy, field emission-scanning electron microscopy (FE-SEM), and photoluminescence emission, are employed to disclose the structural and electronic properties of the α-Ag2WO4 material. First-principles calculations were performed to (i) obtain the relative stability of the six low-index surfaces of α-Ag2WO4; (ii) rationalize the crystal morphologies observed in FE-SEM images (using the Wulff construction); and (iii) determine the energy profiles associated with the transformation process between both morphologies induced by the presence of SDS. Finally, we demonstrate a relationship between morphology and photocatalytic activity, evaluated by photodegradation of Rhodamine B dye under UV light, based on the different numbers of unsaturated superficial Ag and W cations (local coordination, i.e., clusters) of each surface

Controle cognitivo associado à indução de irritabilidade: um estudo de RMf usando recordações autobiográficas

OBJECTIVE: Despite the relevance of irritability emotions to the treatment, prognosis and classification of psychiatric disorders, the neurobiological basis of this emotional state has been rarely investigated to date. We assessed the brain circuitry underlying personal script-driven irritability in healthy subjects (n = 11) using functional magnetic resonance imaging. METHOD: Blood oxygen level-dependent signal changes were recorded during auditory presentation of personal scripts of irritability in contrast to scripts of happiness or neutral emotional content. Self-rated emotional measurements and skin conductance recordings were also obtained. Images were acquired using a 1,5T magnetic resonance scanner. Brain activation maps were constructed from individual images, and between-condition differences in the mean power of experimental response were identified by using cluster-wise nonparametric tests. RESULTS: Compared to neutral scripts, increased blood oxygen level-dependent signal during irritability scripts was detected in the left subgenual anterior cingulate cortex, and in the left medial, anterolateral and posterolateral dorsal prefrontal cortex (cluster-wise p-value < 0.05). While the involvement of the subgenual cingulate and dorsal anterolateral prefrontal cortices was unique to the irritability state, increased blood oxygen level-dependent signal in dorsomedial and dorsal posterolateral prefrontal regions were also present during happiness induction. CONCLUSION: Irritability induction is associated with functional changes in a limited set of brain regions previously implicated in the mediation of emotional states. Changes in prefrontal and cingulate areas may be related to effortful cognitive control aspects that gain salience during the emergence of irritability.OBJETIVO: Apesar da relevância de emoções de irritabilidade para o tratamento, prognóstico e classificação dos transtornos psiquiátricos, as bases neurobiológicas deste tipo de estado emocional foram raramente investigadas até hoje. Este estudo avaliou os circuitos cerebrais subjacentes à irritabilidade induzida por scripts pessoais em voluntários saudáveis (n = 11) usando ressonância magnética funcional. MÉTODO: Mudanças no sinal dependente do nível de oxigenação sanguínea (blood-oxygen level dependent signal) foram registradas durante a apresentação por via auditiva de scripts pessoais de irritabilidade em contraste com scripts de felicidade ou de conteúdo emocional neutro. Escores em escalas de autoavaliação emocional e medidas de condutância da pele também foram obtidos. A aquisição de imagens foi realizada em aparelho de ressonância magnética de 1,5 T. Os mapas de ativação cerebral foram construídos a partir das imagens individuais, e as diferenças entre as condições experimentais foram investigadas utilizando testes não-paramétricos baseados em permutações. RESULTADOS: Em comparação com scripts neutros, a apresentação de scripts de irritabilidade levou a aumentos de sinal dependente do nível de oxigenação sanguínea na porção subgenual do giro do cíngulo anterior esquerdo e nas porções medial, ântero-lateral e póstero-lateral do córtex pré-frontal dorsal (cluster-wise p-valor < 0,05). Enquanto o envolvimento do cíngulo anterior subgenual e do córtex pré-frontal dorsal antero-lateral surgiu apenas em associação com o estado de irritabilidade, aumentos do sinal dependente do nível de oxigenação sanguínea nas porções dorso-medial e dorsal póstero-lateral do córtex pré-frontal também estiveram presentes durante indução de felicidade. CONCLUSÃO: Indução de irritabilidade está associada a mudanças de atividade funcional num conjunto restrito de regiões cerebrais previamente implicadas na mediação de estados emocionais. Mudanças na atividade de porções do giro do cíngulo e pré-frontais podem estar relacionadas a esforço de controle cognitivo associado à expressão de emoções de irritabilidade

An efficient synthesis route of 'Na IND.2''V IND.6''O IND.16.n''H IND.2'O nanowires in hydrothermal conditions

Na2V6O16·nH2O nanowires were synthesized using an environmentally friendly and one-step low-temperature hydrothermal route. The synthesis involved the hydrothermal reaction between V2O5, H2O2 and NaOH, without the addition of any organic surfactants or inorganic ions. X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and thermal gravimetric analysis (TGA) techniques were used to characterize the structure, morphology, chemical composition and thermal stability of the nanostructured samples. High purity hydrated Na2V6O16·nH2O nanowires of diameters around 20–30 nm can be more efficiently obtained when subject to hydrothermal treatment at 140 °C for 24 h. The variation in the electronic and local atomic structure was analyzed using X-ray absorption spectroscopy (XAS). Based on the results obtained from the present study, a mechanism for the formation of Na2V6O16·nH2O nanowires in hydrothermal conditions was proposed.FAPESPCNP

Anomalous oriented attachment growth behavior on SnO2 nanocrystals

This work reports a detailed characterization of an anomalous oriented attachment behaviour for SnO2 nanocrystals. Our results evidenced an anisotropic growth for two identical 〈110〉 directions, which are equivalent according to the SnO2 crystallographic structure symmetry. A hypothesis is proposed to describe this behaviour