The interplay between pore size and wettability in solid-templated silica films

In recent years, the attention to templated SiO2 nanomaterials is particularly focused to film structures, for several different applications. Beside the use of MCM-41 mesoporous silica types, solid templating agents such as polystyrene (PS) latex have been adopted in order to create a morphologically different porosity network, characterized no more by cylindrical pores, but by spherical and possibly interconnected cavities. In the present work, a silica sol was prepared and deposited on conductive glass in a mixture with a PS latex suspension. A careful adjustment of the preparation procedure was conducted and allowed stable, reproducible and electrochemically performing mesoporous thin films to be synthesized. Especially, the sol composition, the controlled ageing procedure, the right template to silica precursor ratio and the deposition procedure parameters revealed to be pivotal for the obtainment of homogeneous and transparent silica thin films. In this context, the physicochemical properties of the films as well as the SiO2 sol were studied. For example, Dynamic Light Scattering (DLS) analyses allowed the dimensions of the silica nuclei promoting the obtainment of the deposited layers to be quantified as a function of the sol ageing. Both the number of successive deposited layers and the dimension of the template (30, 60, 100 nm) were varied. In this sense, aspects pertaining the morphological features of the silica films were deeply characterized by FE-SEM and AFM analyses. Multi-layered depositions allowed an interconnected porous structure to be created, while the influence of the template diameter affected not only the morphology of the film, but above all the diffusion properties of electrochemically active species to the conductive surface of the substrate. In this regard, the electrochemical properties of the prepared devices were compared to thin films in which no templating agent was adopted, revealing large differences both by Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). Electrochemical results were also interpreted in the light of water contact angle measurements. The wettability of the samples surface revealed to be a crucial parameter for the sensing properties of the films and was found to be in complete agreement with roughness data provided by AFM measurements, according to the Wenzel model. Moreover, the study of the optical properties by UV-vis transmittance spectroscopy revealed nonreflective properties with respect to the pristine substrate, thus opening the path to other possible applications, e.g. in the field of optical devices

Electrochemical characterization of insulating silica-modified electrodes : Transport properties and physicochemical features

The effect of depositing different numbers of insulating layers from a silica sol onto an ITO support was investigated to elucidate the changes occurring to diffusion and transfer mechanisms compared with bare electrodes. The electrochemical studies highlighted unexpected trends, which were discussed with respect to literature models and interpreted in the light of the physicochemical characterization (by FE-SEM, AFM, UV-vis transmittance) and particularly the hydrophilicity of the layers

Controlled Mesostructures of Solid-Templated Silica: Preparation and Electrochemical Characterization

In the past decades, mesoporous silica materials characterized by well-ordered microstructure and size- and shape-controlled pores have attracted much attention for the development of functional thin films for advanced applications in catalysis and electrocatalysis, sensors and actuators, separation technologies, micro- and nano-electronic engineering and science [1-3]. In this work, a silica sol in mixture with a polystyrene latex suspension was deposited on ITO conductive glass supports modifying the dimension of the template (30, 60, 100 nm) and the number of successive multi-layered depositions. After the template removal, stable, homogeneous and reproducible transparent thin films were prepared, in which an interconnected porous structure was obtained. The morphological features and the physicochemical and optical properties of the films were studied by Dynamic Light Scattering (DLS), FE-SEM, AFM, UV-vis transmittance spectroscopy analyses. Moreover, a deep electrochemical characterization was also performed by Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) measurements. In particular, the use of two redox mediator probes [(K4Fe(CN)6) and (Ru(NH3)6Cl3)], presenting opposite charge and different diffusional behaviour, allowed the comprehension of the mass and charge transfer phenomena in the silica negatively charged mesochannels (isoelectric point around 2-3), evidencing the effects of spatial confinement and charge selection properties (Figure 1). Figure 1. Cyclic voltammograms registered at electrodes modified with a single layer (a,b) or multilayers (c) of silica with different pore sizes (30, 60, 100 nm) in the presence of 3 mM (a) [Fe(CN)6]4-/[Fe(CN)6]3- and (b-c) [Ru(NH3)6]3+/[Ru(NH3)6]4+. Electrochemical results were also interpreted in the light of water contact angle measurements: samples surface wettability revealed to be a crucial parameter for the sensing properties of the films, in complete agreement with roughness data provided by AFM measurements, according to the Wenzel model. The easiness of preparation and the interesting properties of these devices pave the way towards their use in trace electroanalysis. References [1] M. Ogawa, Chem. Rec., (2017), 17, 217-232. [2] A. Walcarius, E. Sibottier, M. Etienne, J. Ghanbaja, Nature Mat., (2007), 6, 602-608. [3] F. Yan, X. Lin, B. Su, Analyst, (2016), 141, 3482-3495

Prediagnostic Levels of Copper and Zinc and Breast Cancer Risk in the ORDET Cohort

Background: Case–control studies show that copper (Cu) is high and zinc (Zn) low in blood and urine of women with breast cancer compared with controls. Methods: To assess whether prediagnostic Cu and Zn are associated with breast cancer risk, OR of breast cancer according to Cu, Zn, and Cu/Zn ratio in plasma and urine was estimated in a nested case–control study within the ORDET cohort, using conditional logistic regression adjusted for multiple variables: First 496 breast cancer cases and matched controls, diagnosed ≥2 years after recruitment (to eliminate reverse causation) were analyzed. Then all eligible cases/controls were analyzed with stratification into years from recruitment to diagnosis. Results: For women diagnosed ≥2 years, compared with lowest tertiles, breast cancer risk was higher in the highest tertile of plasma Cu/Zn ratio (OR, 1.75; 95% CI, 1.21–2.54) and the highest tertile of both plasma and urine Cu/Zn ratio (OR, 2.37; 95% CI, 1.32–4.25). Risk did not vary with ER/PR/HER2 status. For women diagnosed <2 years, high Cu/Zn ratio was strongly associated with breast cancer risk. Conclusions: Our prospective findings suggest that increased Cu/Zn ratio in plasma and urine may be both an early marker of, and a risk factor for, breast cancer development. Further studies are justified to confirm or otherwise our results and to investigate mechanisms. Impact: Our finding that prediagnostic Cu/Zn ratio is a strong risk factor for breast cancer development deserves further investigation and, if confirmed, might open the way to interventions to reduce breast cancer risk in women with disrupted Cu/Zn homeostasis

A comparison of complementary measures of vitamin B6 status, function, and metabolism in the European Prospective Investigation into Cancer and Nutrition (EPIC) study

Background Vitamin B6 insufficiency has been linked to increased risk of cancer and other chronic diseases. The circulating concentration of pyridoxal 5′-phosphate (PLP) is a commonly used measure of vitamin B6 status. Ratios of substrates indicating PLP coenzymatic function and metabolism may be useful complementary measures to further explore the role of vitamin B6 in health. Objectives We explored the sensitivity of 5 outcomes, namely PLP concentration, homocysteine:cysteine (Hcy:Cys), cystathionine:cysteine (Cysta:Cys), the 3´-hydroxykynurenine ratio (HKr), and the 4-pyridoxic acid ratio (PAr) to vitamin B6 intake as well as personal and lifestyle characteristics. Medthods Dietary intake and biomarker data were collected from participants from 3 nested case-control studies within the European Prospective Investigation into Cancer and Nutrition (EPIC). Bayesian regression models assessed the associations of the 5 biomarker outcomes with vitamin B6 intake and personal and lifestyle covariates. Analogous models examined the relations of Hcy:Cys, Cysta:Cys, and HKr with PLP. Results In total, 4608 participants were included in the analyses. Vitamin B6 intake was most strongly associated with PLP, moderately associated with Hcy:Cys, Cysta:Cys, and HKr, and not associated with PAr (fold change in marker given a doubling of vitamin B6 intake: PLP 1.60 [95% credible interval (CrI): 1.50, 1.71]; Hcy:Cys 0.87 [95% CrI: 0.84, 0.90]; Cysta:Cys 0.89 [95% CrI: 0.84, 0.94]; HKr 0.88 [95% CrI: 0.85, 0.91]; PAr 1.00 [95% CrI: 0.95, 1.05]). PAr was most sensitive to age, and HKr was least sensitive to BMI and alcohol intake. Sex and menopause status were strongly associated with all 5 markers. Conclusions We found that 5 different markers, capturing different aspects of vitamin B6–related biological processes, varied in their associations with vitamin B6 intake and personal and lifestyle predictors