Thin-layer chromatography on silica gel G of some phenol carboxylic acids

Kurzmitteilun

A Concerted Electrochemical and Theoretical Investigation of the Ag/TiO2 nano-heterojunction

Suitably designed nano-heterojunctions are able to enhance synergistic functionalities of different materials yielding to \u201cbrave new systems\u201d with innovative and sometimes unexpected physicochemical properties [1]. However, the complete understanding of these devices has to be deeply studied. In this work, a concerted theoretical and electrochemical investigation is proposed to gain insights into a metal-semiconductor interface, namely that created by the silver/anatase hybrid nanocomposite, a promising material for advanced sensing applications [2]. In particular, it provided the first photorenewable and anti-fouling sensor device, enhancing the analytical limits in terms of accuracy, sensitivity, detection limits, and photoactivity [3]. Furthermore, the hybrid material is proven to be extremely robust against aging, showing complete regeneration, also after one-year storage. The electrochemical/electroanalytical virtues of the Ag/TiO2 junction were evaluated in terms of current densities and reproducibility, providing their explanation at the atomic-scale level and demonstrating how and why the final device can act as silver-cation positive electrode [4]. Moreover, Cyclic Voltammetry and Electrochemical Impedance Spectroscopy were used in combination with periodic plane-wave DFT calculations, giving comparable qualitative but also quantitative results. In particular, we theoretically estimated the overall amount of electron transfer toward the semiconductor side of the interface at equilibrium and suitably designed electrochemical experiments, which strictly agree with the theoretical charge transfer estimates. Moreover, photoelectrochemical measurements and theoretical predictions show the unique permanent charge separation occurring in the device [4]. [1] A.V. Emeline, V.N. Kuznetsov, V.K. Ryabchuk, N. Serpone, Environ. Sci. Pollut. Res., 2012, 19, 3666\u20133675. [2] G. Soliveri, V. Pifferi, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, K. Sparnacci, L. Falciola, Analyst, 2015, 140, 1486\u20131494. [3] V. Pifferi, G. Soliveri, G. Panzarasa, G. Cappelletti, D. Meroni, L. Falciola, Anal. Bioanal. Chem., 2016, 408, 7339\u20137349. [4] G. Di Liberto, V. Pifferi, L. Lo Presti, M. Ceotto, L. Falciola, J. Phys. Chem. Lett., 2017, 8, 5372\u20135377

Mesoporous silica networks with improved diffusion and interference-rejecting properties for electroanalytical sensing

Mesoporous silica materials characterized by well-ordered microstructure and size- and shape-controlled pores have attracted much attention in the last years. These systems can be used for the development of functional thin films for advanced applications in catalysis and electrocatalysis, sensors and actuators, separation techniques, micro- and nano-electronic engineering [1-2]. In this work, \u201cinsulating\u201d and mesoporous silica films were prepared by spin coating a home-made silica sol on a cleaned ITO glass support. The mesoporosity was controlled by the use of Polystyrene (PS) latex beads with different dimensions (30-60-100 nm) as template. The number of successive multi-layer depositions was varied (1-2-3-5 layers) and after the template removal, stable, homogeneous and reproducible transparent films were obtained, characterized by an interconnected porous structure. The morphological features and the physicochemical and optical properties of the films and/or sol-precursors were studied by DLS, FE-SEM, AFM, UV-vis transmittance spectroscopy and wettability analyses. Moreover, a deep electrochemical characterization was also performed by Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). 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 transport and charge transfer phenomena, evidencing the effects of spatial confinement and charge selection. In the case of \u201cinsulating\u201d films prepared without the use of PS latexes, we proved an experimental evidence for theoretical models [3] concerning electroinactive layer-modified electrodes, with a scan-rate-dependent variation of the CV shape due to a progressive increase in the diffusion coefficient inside the insulating layer. A complex balance between diverging effects (higher hydrophilicity and insulating behavior effects of silica) when increasing the numbers of layers was also observed [4]. In the case of mesoporous layers, a better electrochemical response of smaller pores and of thicker layers was found, due to two main cooperative phenomena: i) a diffusion modification from fully planar to radial-convergent at the pore-silica interface due to surface porosity; ii) the presence of pores in a hydrophilic matrix which leads to a capillary pull effects, stronger in the case of smaller hydrophilic pores. The easiness of preparation and the interesting properties of these devices pave the way towards their use in many fields, particularly trace electroanalysis in real matrices. In fact, for example, the porous and properly charged network is able to exclude interfering macromolecules (mucin in our case), preventing electrode biofouling and enhancing the performances of the sensor towards dopamine detection. References [1] M. Ogawa, Chem. Rec. 17 (2017) 217-232. [2] A. Walcarius, Chem. Soc. Rev. 42 (2013) 4098-4140. [3] D. Menshykau, R.G. Compton, Langmuir 25 (2009) 2519\u20132529. [4] V. Pifferi, L. Rimoldi, D. Meroni, F. Segrado, G. Soliveri, S. Ardizzone, L. Falciola, Electrochem. Commun. 81 (2017) 102-105

A Concerted Investigation For Metal/Semiconductor Nanointerface : Interlayer Charge Transfer At Ag/TiO2

In the field of hybrid materials, suitably designed nanoheterojunctions enhance synergistic functionalities and allow to obtain \u201cbrave new materials\u201d with physicochemical properties that are not simply the addition of the precursors\u2019 ones, but are completely new, different, and sometimes unexpected. For these reasons, the use of them has paved the way toward promising applications in many fields, such as electrocatalysis, photocatalysis, electroanalysis, and environmental chemistry, impacting on the everyday life [1]. However, research on such systems is most often dominated by trial and error procedures, while a deep atomistic understanding of the phenomena inside the junction region driving appropriate design of the final device is missing. Here, a concerted theoretical and electrochemical investigation is proposed to gain insights into the important class of heterojunctions made by metal-semiconductor interfaces. The presented case of study is the silver/anatase hybrid nanocomposite, a very promising material for advanced sensing applications [2]. Considering that in most cases titania semiconductors are useless in electroanalysis and silver is subject to fouling and oxidation/passivation, such broad outcomes were totally unexpected. Specifically, Ag/TiO2 interfase provided the first photorenewable sensor device, pushing the limits in terms of accuracy, sensitivity, detection limits, and photoactivity [3]. Despite the ongoing research, a quantitative and comprehensive understanding of the physics behind this nanocomposite is still missing, thus preventing its full exploitation and the extension of the same paradigm to other systems and devices. In particular, cyclic voltammetry and electrochemical impedance spectroscopy are used in combination with periodic plane-wave DFT calculations, giving comparable qualitative, but also quantitative results. We measure the exceptional electrochemical virtues of the Ag/TiO2 junction in terms of current densities and reproducibility, providing their explanation at the atomic-scale level and demonstrating how and why silver acts as a positive electrode [4]. We theoretically estimate the overall amount of electron transfer toward the semiconductor side of the interface at equilibrium and suitably designed electrochemical experiments strictly agree with the theoretical charge transfer estimates. Moreover, photoelectrochemical measurements and theoretical predictions show the unique permanent charge separation occurring in the device, possible because of the synergy of Ag and TiO2, which exploits in a favorable band alignment, in a smaller electron\u2013hole recombination rate and in a reduced carrier mobility when electrons cross the metal\u2013semiconductor interface. Finally, the hybrid material is proven to be extremely robust against aging, showing complete regeneration, even after one year [4]. [1] A.V. Emeline, V.N. Kuznetsov, V.K. Ryabchuk, N. Serpone, Environ. Sci. Pollut. Res. 19 (2012) 3666\u20133675. [2] G. Soliveri, V. Pifferi, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, K. Sparnacci, L. Falciola, Analyst 140 (2015) 1486\u20131494. [3] V. Pifferi, G. Soliveri, G. Panzarasa, G. Cappelletti, D. Meroni, L. Falciola, Anal. Bioanal. Chem. 408 (2016) 7339\u20137349. [4] G. Di Liberto, V. Pifferi, L. Lo Presti, M. Ceotto, and L. Falciola, J. Phys. Chem. Lett. 8 (2017) 5372\u20135377

Interactions between permeation and gating in the TMEM16B/anoctamin2 calcium-activated chloride channel

At least two members of the TMEM16/anoctamin family, TMEM16A (also known as anoctamin1) and TMEM16B (also known as anoctamin2), encode Ca2+-activated Cl- channels (CaCCs), which are found in various cell types and mediate numerous physiological functions. Here, we used whole-cell and excised inside-out patch-clamp to investigate the relationship between anion permeation and gating, two processes typically viewed as independent, in TMEM16B expressed in HEK 293T cells. The permeability ratio sequence determined by substituting Cl- with other anions (PX/PCl) was SCN- > I- > NO3- > Br- > Cl- > F- > gluconate. When external Cl- was substituted with other anions, TMEM16B activation and deactivation kinetics at 0.5 μM Ca2+ were modified according to the sequence of permeability ratios, with anions more permeant than Cl- slowing both activation and deactivation and anions less permeant than Cl- accelerating them. Moreover, replacement of external Cl- with gluconate, or sucrose, shifted the voltage dependence of steady-state activation (G-V relation) to more positive potentials, whereas substitution of extracellular or intracellular Cl- with SCN- shifted G-V to more negative potentials. Dose-response relationships for Ca2+ in the presence of different extracellular anions indicated that the apparent affinity for Ca2+ at +100 mV increased with increasing permeability ratio. The apparent affinity for Ca2+ in the presence of intracellular SCN- also increased compared with that in Cl-. Our results provide the first evidence that TMEM16B gating is modulated by permeant anions and provide the basis for future studies aimed at identifying the molecular determinants of TMEM16B ion selectivity and gating. © 2014 Betto et al

Evaluation of a pipeline for simulation, reconstruction, and classification in ultrasound-aided diffuse optical tomography of breast tumors

SIGNIFICANCE: Diffuse optical tomography is an ill-posed problem. Combination with ultrasound can improve the results of diffuse optical tomography applied to the diagnosis of breast cancer and allow for classification of lesions. AIM: To provide a simulation pipeline for the assessment of reconstruction and classification methods for diffuse optical tomography with concurrent ultrasound information. APPROACH: A set of breast digital phantoms with benign and malignant lesions was simulated building on the software VICTRE. Acoustic and optical properties were assigned to the phantoms for the generation of B-mode images and optical data. A reconstruction algorithm based on a two-region nonlinear fitting and incorporating the ultrasound information was tested. Machine learning classification methods were applied to the reconstructed values to discriminate lesions into benign and malignant after reconstruction. RESULTS: The approach allowed us to generate realistic US and optical data and to test a two-region reconstruction method for a large number of realistic simulations. When information is extracted from ultrasound images, at least 75% of lesions are correctly classified. With ideal two-region separation, the accuracy is higher than 80%. CONCLUSIONS: A pipeline for the generation of realistic ultrasound and diffuse optics data was implemented. Machine learning methods applied to a optical reconstruction with a nonlinear optical model and morphological information permit to discriminate malignant lesions from benign ones

Monitoring Neoadjuvant Chemotherapy Through Time Domain Diffuse Optical Spectroscopy in Breast Cancer Patients: Preliminary Clinical Results

The purpose of this clinical study is to monitor NeoAdjuvant Chemotherapy through time domain Diffuse Optical Spectroscopy, correlate the optical results with conventional imaging techniques and pathological response and eventually predict the efficacy of NAC in breast cancer patients. Our seven wavelength (635 -1060 nm) optical mammograph is used to perform non-invasive measurements on patients undergoing NAC in this study. The broad spectral range helps us to fully analyze tissue composition, that includes hemoglobin, water lipids and collagen concentration, to track the tumor response during the course of the therapy. In this paper, we present the preliminary results of five patients

Preliminary Evidence of the Efficacy of Time-Resolved Broad-Spectrum Optical Mammography in Monitoring Neoadjuvant Chemotherapy

We present initial results of a clinical trial involving breast cancer patients under neoadjuvant chemotherapy, monitored through our time-resolved optical mammograph. Besides hemoglobin, water and lipids, we assess collagen concentration systematically for the first time