Enhance Ethanol Sensing Performance of Fe-Doped Tetragonal SnO2 Films on Glass Substrate with a Proposed Mathematical Model for Diffusion in Porous Media.

This research enhances ethanol sensing with Fe-doped tetragonal SnO2 films on glass, improving gas sensor reliability and sensitivity. The primary objective was to improve the sensitivity and operational efficiency of SnO2 sensors through Fe doping. The SnO2 sensors were synthesized using a flexible and adaptable method that allows for precise doping control, with energy-dispersive X-ray spectroscopy (EDX) confirming homogeneous Fe distribution within the SnO2 matrix. A morphological analysis showed a surface structure ideal for gas sensing. The results demonstrated significant improvement in ethanol response (1 to 20 ppm) and lower temperatures compared to undoped SnO2 sensors. The Fe-doped sensors exhibited higher sensitivity, enabling the detection of low ethanol concentrations and showing rapid response and recovery times. These findings suggest that Fe doping enhances the interaction between ethanol molecules and the sensor surface, improving performance. A mathematical model based on diffusion in porous media was employed to further analyze and optimize sensor performance. The model considers the diffusion of ethanol molecules through the porous SnO2 matrix, considering factors such as surface morphology and doping concentration. Additionally, the choice of electrode material plays a crucial role in extending the sensor's lifespan, highlighting the importance of material selection in sensor design.

Improving Hazardous Gas Detection Behavior with Palladium Decorated SnO2 Nanobelts Networks.

Transparent Conductive Oxides (TCOs) have been widely used as sensors for various hazardous gases. Among the most studied TCOs is SnO2, due to tin being an abundant material in nature, and therefore being accessible for moldable-like nanobelts. Sensors based on SnO2 nanobelts are generally quantified according to the interaction of the atmosphere with its surface, changing its conductance. The present study reports on the fabrication of a nanobelt-based SnO2 gas sensor, in which electrical contacts to nanobelts are self-assembled, and thus the sensors do not need any expensive and complicated fabrication processes. The nanobelts were grown using the vapor-solid-liquid (VLS) growth mechanism with gold as the catalytic site. The electrical contacts were defined using testing probes, thus the device is considered ready after the growth process. The sensorial characteristics of the devices were tested for the detection of CO and CO2 gases at temperatures from 25 to 75 °C, with and without palladium nanoparticle deposition in a wide concentration range of 40-1360 ppm. The results showed an improvement in the relative response, response time, and recovery, both with increasing temperature and with surface decoration using Pd nanoparticles. These features make this class of sensors important candidates for CO and CO2 detection for human health.

Nondestructive, reagent-free, low-volume fluidic set-up to study biofilms by using a transparent electrode, allowing simultaneous electrochemical and optical measurements.

AIMS: The aim was to develop an electrochemical/optical set-up and correlate it (as validation) with other chemical and physical methods to obtain a simple and cost-effective system to study biofilm formation. METHODS AND RESULTS: A simple microfluidic cell and methods allowed continuous monitoring of the first, critical steps of microbial attachment. We monitored sulfate-reducing bacteria (SRB) at the early stages of biofilm formation. Herein, we studied the formation and adherence of SRB consortium biofilms over an indium tin oxide (ITO) conducting surface using microbiological and chemical methods, microscopic observations [scanning electron microscopy (SEM) and optical], and electrochemical impedance spectroscopy (EIS) measurements. The SRB biofilm formation was evaluated for 30 d by SEM and EIS. Charge transfer resistance decreased when the microbial population colonized the electrode. The monitoring of early-stage biofilm formation was performed using EIS at a single frequency of 1 Hz during the first 36 h. CONCLUSIONS: The simultaneous use of optical, analytical, and microbiological methods allowed us to connect the kinetics of the growth of the microbial consortium to the values obtained via the electrochemical technique. The simple setup we present here can help laboratories with limited resources to study biofilm attachment and facilitates the development of various strategies to control biofilm development in order to avoid damage to metallic structures (microbiologically influenced corrosion, MIC) or the colonization of other industrial structures and medical devices.

Synthesis of PMMA Microspheres with Tunable Diameters: Evaluation as a Template in the Synthesis of Tin Oxide Coatings.

The synthesis of polymethyl methacrylate (PMMA) spheres with different sizes has been a challenge. PMMA has promise for future applications, e.g., as a template for preparing porous oxide coatings by thermal decomposition. Different amounts of SDS as a surfactant are used as an alternative to control PMMA microsphere size through the formation of micelles. The objectives of the study were twofold: firstly, to determine the mathematical relationship between SDS concentration and PMMA sphere diameter, and secondly, to assess the efficacy of PMMA spheres as templates for SnO2 coating synthesis and their impact on porosity. The study used FTIR, TGA, and SEM techniques to analyze the PMMA samples, and SEM and TEM techniques were used for SnO2 coatings. The results showed that PMMA sphere diameter could be adjusted by varying the SDS concentration, with sizes ranging from 120 to 360 nm. The mathematical relationship between PMMA sphere diameter and SDS concentration was determined with a y = axb type equation. The porosity of SnO2 coatings was found to be dependent on the PMMA sphere diameter used as a template. The research concludes that PMMA can be used as a template to produce oxide coatings, such as SnO2, with tunable porosities.

Chitosan/genipin modified electrode for voltammetric determination of interleukin-6 as a biomarker of sepsis.

Ultrasensitive electroanalytical monitoring of interleukin-6 levels in serum samples has emerged as a valuable tool for the early diagnosis of inflammatory diseases. Despite its advantages, there is a lack of strategies for the label-free voltammetric determination of cytokines. Here, a novel chitosan/genipin modified fluorine tin oxide electrode was developed providing an in-situ hydrogel formation (FTO/CSG). This platform was applied for the detection of interleukin-6, a major pro-inflammatory cytokine. Transmission electron microscopy (TEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) indicated genipin serves as an efficient green cross-linker to build the immunosensing platform (FTO/CSG/anti-IL-6). EIS showed an increase in charge transfer resistance from 326 to 1360 kΩ after the immobilization of anti-IL-6 antibodies. By square wave voltammetry, this method achieved a detection limit of 0.03 pg mL-1 with a wide linear range of 0.05-1000 pg mL-1. Additionally, it displayed a high selectivity index when tested in the presence of three inflammatory cytokines as interfering proteins: IL-12, IL-1ß, and TNF-α. The sample matrix effect showed a peak current variation lower than 5 %. The novel method was applied for the quantification of IL-6 in serum samples of septic mice. No statistical differences were observed between the standard ELISA and the proposed method using a confidence level of 95 %.

Manganese Dioxide Nanoparticles Prepared by Laser Ablation as Materials with Interesting Electronic, Electrochemical, and Disinfecting Properties in Both Colloidal Suspensions and Deposited on Fluorine-Doped Tin Oxide.

Nanoparticles (NPs) of α-MnO2 have high applicability in photoelectrochemical, heterogeneous photocatalysis, optical switching, and disinfection processes. To widen this panorama about MnO2 NPs, the formation of this material by laser ablation and deposition by dip-coating on fluorine-doped tin oxide (FTO), were considered in this study. The optical, spectroscopic, electrochemical characterization, and the evaluation of the antimicrobial activity, plus the photocatalytic response, were measured herein in colloidal media and deposited. For the deposition of NPs on FTO sheet, an anode is produced with a pseudocapacitive behavior, and 2.82 eV of band gap (GAP) in comparison with colloidal NPs for a value of 3.84 eV. Both colloidal suspension and deposited NPs have intrinsic antibacterial activity against two representative microorganisms (E. coli and S. aureus), and this biological activity was significantly enhanced in the presence of UVA light, indicating photocatalytic activity of the material. Thus, both the colloidal suspension and deposited NPs can act as disinfecting agents themselves or via light activation. However, an antibacterial behavior different for E. coli and S. aureus was observed, in function of the aggregation state, obtaining total E. coli disinfection at 30 min for deposited samples on FTO.

Toxicity of engineered nanomaterials with different physicochemical properties and the role of protein corona on cellular uptake and intrinsic ROS production.

The Organisation for Economic Co-operation and Development has listed thirteen engineered nanomaterials (ENM) in order to investigate their toxicity on human health. Silicon dioxide (SiO2) and titanium dioxide (TiO2) are included on that list and we added indium tin oxide (ITO) nanoparticles (NPs) to our study, which is not listed on OECD suggested ENM to be investigated, however ITO NPs has a high potential of industrial production. We evaluate the physicochemical properties of SiO2 NPs (10-20 nm), TiO2 nanofibers (NFs; 3 µm length) and ITO NPs (<50 nm) and the impact of protein-corona formation on cell internalization. Then, we evaluated the toxicity of uncoated ENM on human lung epithelial cells exposed to 10 and 50 µg/cm2 for 24 h. TiO2 NFs showed the highest capability to adsorb proteins onto the particle surface followed by SiO2 NPs and ITO NPs after acellular incubation with fetal bovine serum. The protein adsorption had no impact on Alizarin Red S conjugation, intrinsic properties for reactive oxygen (ROS) formation or cell uptake for all types of ENM. Moreover, TiO2 NFs induced highest cell alterations in human lung epithelial cells exposed to 10 and 50 µg/cm2 while ITO NPs induced moderated cytotoxicity and SiO2 NPs caused even lower cytotoxicity under the same conditions. DNA, proteins and lipids were mainly affected by TiO2 NFs followed by SiO2 NPs with toxic effects in protein and lipids while limited variations were detected after exposure to ITO NPs on spectra analyzed by Fourier Transform Infrared Spectroscopy.

Indium and tin recovery from waste LCD panels using citrate as a complexing agent.

In this work, an environmentally-friendly leaching process for the recovery of indium (In) and tin (Sn) from LCD panel waste was investigated. Easily degradable citrates (C6H5O73-), i.e., sodium citrate and citric acid, were used as complexing agents. The morphology and composition of the species present in the LCD powder before and after the leaching processes were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The concentrations of In, Sn, and iron (Fe) present in the leachate were determined by atomic absorption spectrometry (AAS). The necessary thermodynamic conditions for achieving substantial In recovery were established by using MEDUSA software. The optimal process conditions were determined experimentally by varying the initial citrate concentration as well as by using reducing or oxidizing media, respectively hydrazine (N2H4) or hydrogen peroxide (H2O2). It was found that using N2H4 in a citrate solution as a reducing agent enhances the leaching efficiency. However, high concentrations of Sn and Fe with respect to In were found in the LCD powder. Therefore, a pretreatment processes to first remove the excess of Sn and Fe, which compete with In for the citrate, was implemented. Leaching with 1 M citrate, 0.2 M N2H4, at pH = 5, using sodium hydroxide (NaOH) at solid:liquid (S:L) ratio of 20 g∙L-1, yielded a remarkably high In recovery of 98.9% after 16.6 h.

A Study of the CO Sensing Responses of Cu-, Pt- and Pd-Activated SnO2 Sensors: Effect of Precipitation Agents, Dopants and Doping Methods.

In this work, we report the synthesis of Cu, Pt and Pd doped SnO2 powders and a comparative study of their CO gas sensing performance. Dopants were incorporated into SnO2 nanostructures using chemical and impregnation methods by using urea and ammonia as precipitation agents. The synthesized samples were characterized using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HR-TEM). The presence of dopants within the SnO2 nanostructures was evidenced from the HR-TEM results. Powders doped utilizing chemical methods with urea as precipitation agent presented higher sensing responses compared to the other forms, which is due to the formation of uniform and homogeneous particles resulting from the temperature-assisted synthesis. The particle sizes of doped SnO2 nanostructures were in the range of 40-100 nm. An enhanced sensing response around 1783 was achieved with Cu-doped SnO2 when compared with two other dopants i.e., Pt (1200) and Pd:SnO2 (502). The high sensing response of Cu:SnO2 is due to formation of CuO and its excellent association and dissociation with adsorbed atmospheric oxygen in the presence of CO at the sensor operation temperature, which results in high conductance. Cu:SnO2 may thus be an alternative and cost effective sensor for industrial applications.

CO Gas Sensing Properties of Pure and Cu-Incorporated SnO2 Nanoparticles: A Study of Cu-Induced Modifications.

Pure and copper (Cu)-incorporated tin oxide (SnO2) pellet gas sensors with characteristics provoking gas sensitivity were fabricated and used for measuring carbon monoxide (CO) atmospheres. Non-spherical pure SnO2 nano-structures were prepared by using urea as the precipitation agent. The resultant SnO2 powders were ball milled and incorporated with a transition metal, Cu, via chemical synthesis method. The incorporation is confirmed by high-resolution transmission electron microscope (HRTEM) analysis. By utilizing Cu-incorporated SnO2 pellets an increase in the CO sensitivity by an order of three, and a decrease in the response and recovery times by an order of two, were obtained. This improvement in the sensitivity is due to two factors that arise due to Cu incorporation: necks between the microparticles and stacking faults in the grains. These two factors increased the conductivity and oxygen adsorption, respectively, at the pellets' surface of SnO2 which, in turn, raised the CO sensitivity.

Implementation y evaluación de una nariz electrónica para la detección de alcoholes lineales / Implementation and evaluation of an electronic nose for the alcohols detection / Implementação e avaliação de um nariz eletrônico para detectar álcoois lineares

Se desarrolló una nariz electrónica que permite la detección de alcoholes de manera sencilla y económica en comparación con las narices electrónicas tradicionales. Estábasada en cuatro sensores de gas de SnO2 (dos comerciales y dos fabricados en el laboratorio), un sistema neumático irregular, un hardware y software para adquisición de datos y un software de reconocimiento de patrones. Se evaluó el comportamiento de la nariz y las condiciones de trabajo con muestras de vapor de alcoholes (metanol, etanol, n-butanol y 1-2 octanol) y se determinó que los alcoholes se pueden detectar con el arreglo de sensores preparado y pueden diferenciarse entre sí haciendo uso del análisis estadístico de componentes principales (PCA). El orden de detección encontrado para los alcoholes lineales fue el siguiente: metanol > etanol > n-butanol > 1-octanol. Se encontró también que haciendo uso del análisis de componentes principales (PCA) y realizando una normalización de los datos en el software de reconocimiento de patrones, la varianza total de las muestras también aumenta del 76% al 85%. Esto demuestra que una nariz simple y económica puede clasificar bien las muestras evaluadas.

An electronic nose for the detection of alcohols, easy to use and inexpensive as compared to traditional electronic noses, was developed. This nose is based on four SnO2 gas sensors (two commercial and two homemade), an irregular pneumatic system, hardware and a software for data acquisition and a software for pattern recognition. The nose behavior and the working conditions with vapor samples of alcohols (methanol, ethanol, n-butanol and 1-octanol) were evaluated. Alcohols could be detected with the array of prepared sensors and could be also differentiated from each other by using principal component analysis (PCA). The detection order for linear alcohols followed the order: methanol > ethanol > n-butanol > 1-octanol. It was also found that by using PCA and performing a standardization of data in software pattern recognition so, the total variance of such information increases from 76% up to 85%. This result confirms that a simple and inexpensive nose can rank well the tested samples.

Foi feito um nariz eletrônico que permitiu a detecção de álcoois de jeito simplis e económico em comparacao com os narices electrónicos tradicionais. Estábaseado em quatro sensores de gás SnO2 (dois comerciais e dois feitos no laboratório), um sistema pneumático irregular, hardware e software para aquisição de dados e software de reconhecimento de padrões. Foi avaliado o comportamento do nariz e as condições de trabalho com amostras de vapor de álcoois (metanol, etanol, n-butanol e 1-octanol) determinou-se que os álcoois podem ser detectados com o arranjo de sensores preparado e pode diferenciar-se entre sim usando análise de componentes principais (PCA). A ordem de detecção para os álcoois lineares encontrados foi os seguinte: metanol> etanol> n-butanol> 1-octanol. Verificou-se que, usando análise de componentes principais (PCA) e a execução de uma normalização dos dados no software de reconhecimento de padrões, a variância das amostras também aumenta de 76% para 85%. Esto demostra que um nariz simples e barato pode classificar bem as amostras avaliadas.

Neumoconiosis ocupacional por óxido de estaño / Occupational pneumoconiosis due to tin oxide

Resumen Se presenta el caso de hombre de 34 años con compromiso pulmonar secundario a exposición crónica a soldadura con óxido de estaño. El paciente consulto por tos seca de cuatro meses de evolución asociada a disnea leve y sibilancias ocasionales sin mejoría a tratamiento broncodilatador y con aparición de opacidades pulmonares en vidrio esmerilado hacia los lóbulos superiores, en biopsia transbronquial pulmonar se encuentran zonas de antracosis con macrófagos pardos sin fibrosis, hallazgos compatibles con estañosis. Esta enfermedad es poco frecuente, se relaciona con un curso benigno y debe ser reconocida dentro del grupo de enfermedades ocupacionales para definir el pronóstico del paciente. (Acta Med Colomb 2013; 38: 273-276).

Abstract A case of 34 year old man with lung involvement secondary to chronic exposure to welding with tin oxide. The patient consulted for a four-month history of dry cough associated with mild dyspnea and occasional wheezing without improvement with bronchodilator therapy and appearance of ground glass pulmonary opacities towards the upper lobes. In a transbronchial lung biopsy there are anthracosis areas with brown macrophages without fibrosis, findings consistent with stannosis. This is a rare disease that is associated with a benign course and should be recognized within the group of occupational diseases to define the prognosis of the patient. (Acta Med Colomb 2013; 38: 273-276).