Functional and optical properties of Au :TiO2 nanocomposite films : the influence of thermal annealing

A set of nanocomposite thin films consisting of Au nanoclusters dispersed in a TiO2 dielectric matrix was deposited by reactive magnetron sputtering, and subjected to thermal annealing in vacuum, at temperatures ranging from 200 to 800 ◦C. The obtained results show that the structure and the size of Au clusters, together with the matrix crystallinity, changed as a result of the annealing, and were shown to be able to change the optical properties of the films and keeping good mechanical properties, opening thus a wide number of possible applications. The crystallization of the gold nanoclusters induced by the annealing was followed by a systematic change in the overall coating behaviour, namely the appearance of surface plasmon resonance (SPR) behaviour. This effect enables to tailor the thin films reflectivity, absorbance and colour coordinates, contributing to the importance of this thin film system. The different attained optical characteristics (reflectance values ranging from interference to metallic-like behaviours and colour varying for interference rainbow-like to several tones of red-brownish), associated with a reasonable mechanical resistance of the coatings (good adhesion to different substrates and hardness values ranging from 5 to 7.5 GPa), induce the possibility to use this film system in a wide range of decorative applications.Fundac¸ ão para a Ciência e Tecnologia (FCT) - PTDC/CTM/70037/2006

Development of new decorative coatings based on gold nanoparticles dispersed in an amorphous TiO2 dielectric matrix

The present work is devoted to the optical properties of Au:TiO2 thin films in order to clarify the role of the Au clusters inclusions in the TiO2 dielectric matrix. Three series of films containing about 30 at.% (29.2), 20 at. % (19.8) and 10 at.% (9.3) Au were deposited by dc reactive magnetron sputtering. On thermal annealing in the range from 300 to 800 °C in protective atmosphere, significant changes on the crystalline phases and clusters dimensions were detected. The most promising optical behavior was found for the film 20% Au:TiO2, where the films revealed some colour changes, evolving from several shades of grey to different tones of red. This change in the optical behaviour of the films was found to be correlated with a cluster size increase from 2 to 17 nm. For higher size values (>20 nm) the films, independently of the Au content, showed a golden appearance colour. The optical changes were confirmed by reflectivity and CIELab colour measurements. Regarding the films with 10 and 30 at.% Au, the results confirmed that there is an evident range of compositions and clusters size where the SPR is more evident. Sample A (10 at.% Au) it seems to be in the lower limit of the SPR showing a typical interferometric behavior on the reflectivity measurements, similar to the TiO2 optical behavior. Regarding the 30 at.% Au one, the results seems to indicate that the amount of gold particles and their grain size is in the upper limit to show a SPR activity.Fundação para a Ciência e Tecnologia (FCT) - PTDC/CTM/70037/200

Nanoscale color control of TiO2 films with embedded Au nanoparticles

Article in pressWe demonstrate an efficient nanoscale control of the optical properties of TiO2 films by tuning the Surface Plasmon Resonance (SPR) in the embedded Au nanoparticles. The films were grown by reactive magnetron sputtering. SPR tuning was achieved by different annealings, which affected the shape and size of the Au nanoparticles, and also the phase of the dielectric matrix. These changes promoted the variations on the optical properties. As shown by the modeling of the effective dielectric function of the TiO2/Au in the SPR region, the variation of their optical absorption spectra correlates with morphological changes.Fundação para a Ciência e a Tecnologia (FCT) - PTDC/CTM/70037/2006

Tuning of the surface plasmon resonance in TiO2/Au thin films grown by magnetron sputtering : the effect of thermal annealing

Nanocomposites consisting of a dielectric matrix, such as TiO2, with embedded noble metal nanoparticles (NPs) possess specific optical properties due to the surface plasmon resonance (SPR) effect, interesting for several applications. The aim of this work is to demonstrate that these properties are sensitive to the nanostructure of magnetron-sputtered TiO2/Au thin films, which can be tuned by annealing. We study the role of the shape and size distribution of the NPs, as well as the influence of the crystallinity and phase composition of the host matrix on the optical response of the films. All these characteristics can be modified by vacuum annealing treatments of the deposited films. A theoretical interpretation and modeling of the experimental results obtained is presented. The model involves a modified Maxwell-Garnett approach for the effective dielectric function of the composite (describing the SPR effect) and the transfer matrix formalism for multilayer optics. Input data are based on the experimental information obtained from the detailed structural characterization of the films. It is shown that the annealing treatments can be used for controlling the optical properties of the composite films, making them attractive for decorative coatings.Fundação para a Ciência e a Tecnologia (FCT) - PTDC/CTM/70037/200

Relationship between smoking and acute mountain sickness: a meta-analysis of observational studies

Aims. Previous epidemiological investigations of the relationship between smoking and acutemountain sickness (AMS) risk yielded inconsistent findings.Therefore, a meta-analysis of observational studies was performed to determine whether smoking is related to the development of AMS. Methods. Searches were performed on PubMed, Scopus, Embase, and Web of Science for relevant studies that were published before November 2016 reporting smoking prevalence and AMS. Two evaluators independently selected studies, extracted data, and assessed study quality.Thepooled relative risks (RRs) and 95% confidence intervals (CIs) were obtained using random-effects models. Subgroup analyses were performed according to the type of participant, altitude, and study design. Results. A total of 11 observational studies involving 7,106 participants, 2,408 of which had AMS, were eligible for inclusion in this meta-analysis. The summary RR for AMS comparing smokers to nonsmokers was 1.02 (95% CI: 0.83 to 1.26). Specific analyses for altitude, type of participant, and study design yielded similar results.There was significant heterogeneity for all studies ( = 37.43; < 0.001; 2 = 73%, 95% CI: 51% to 85%). No publication bias was observed (Egger's test: = 0.548, Begg's test: = 0.418). Conclusions.The meta-analysis indicates that no difference was found in AMS risk with regard to smoking status

Protective Ag :TiO2 thin films for pressure sensors in orthopedic prosthesis: the importance of composition, structural and morphological features on the biological response of the coatings

DC reactive magnetron sputtered Ag:TiO2 nanocomposite thin films were developed to be used as protective coatings in pressure sensor devices. The coatings, with Ag content varying from 0 to about 30 at.%, were prepared and characterized in order to study their biological response. The as-deposited samples were annealed in vacuum at 500 °C in order to evaluate the influence of their morphological and structural differences over the response elicited upon contact with simulated bodily fluids and cultured human cells, as well as selected microorganisms. The results showed that the annealing treatment produced less porous films with an enhanced structure, with a significant reduction in structural defects and improved crystallinity. Additionally, samples with higher Ag contents (≥12.8 at.%) exhibited Ag agglomerates/clusters at the surface, a result anticipated from the XRD data. The crystallization of the TiO2 matrix was also observed by XRD analysis, albeit delayed by the dispersion of Ag into the matrix. Biological characterization showed that the antimicrobial activity and cytotoxicity of the coatings were directly related with their composition, closely followed by the particular structural and morphological features, namely those resulting from annealing process.This research is partially sponsored by FEDER funds through the program COMPETE—Programa Operacional Factores de Competitividade and by national funds through FCT—Fundação para a Ciência e a Tecnologia, under the projects PEst-C/EME/UI0285/2011, PTDC/SAU-ENB/116850/2010, PTDC/CTM-NAN/112574/2009P. T Matamá acknowledges FCT for Grant SFRH/BPD/47555/2008

Perspective Chapter: Emerging Infectious Diseases As a Public Health Problem

Emerging infectious diseases (EIDs) can be defined as diseases that have recently appeared in a population or are rapidly increasing in incidence or geographic range. An “emerging infection” refers to either a new infection that has never appeared before or a known infection that has experienced a recent increase in prevalence. The Human Immunodeficiency Virus (HIV) pandemic and Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) outbreaks are prototypical examples of emerging infectious diseases that were not prevalent before the 1980s and 2003, respectively. On the other hand, a “re-emerging infection” is a familiar infection that resurfaces. The influenza A virus pandemics of 1918, 1957, and 1968 serve as prototypical examples of re-emerging infections. This chapter aims to define the concepts of emerging and re-emerging infectious diseases and explore their main causes, the microorganisms involved, and why they can become significant global public health problems

Pre-travel health care attendance among migrant travellers visiting friends and relatives (VFR): a 10-year retrospective analysis

Background: Travellers visiting friends and relatives (VFR) define a specific population of travellers exposed to higher risks for health and safety than tourists. The aim of this study was to assess differentials in pre-travel health care in VFR travellers compared to other travellers. Methods: A retrospective cohort study was performed including attendees of the Travel Medicine Clinic of the Hospital Universitari de Bellvitge, Barcelona, Spain, between January 2007 and December 2017. Results: Over the 10-year period, 47,022 subjects presented to the travel clinic for pre-travel health care, 13.7% of whom were VFR travellers. These showed higher rates of vaccination against yellow fever and meningococcus, but lower rates for hepatitis A, hepatitis B, influenza, rabies, cholera, polio, typhoid IM vaccine and tetanus vaccine boosters. Regarding malaria prevention measures, results highlighted that VFR travellers, when compared with tourists, were more likely to be prescribed with chemoprophylaxis, particularly with mefloquine, than with atovaquone/proguanil. Conclusions: Findings from this large-scale study indicated differences in vaccination rates and completion, as well as in chemoprophylaxis for malaria, between VFR and non-VFR travellers, fostering specific interventions for promoting adherence to pre-travel health advice among migrant travellers