Raman Study of Novel Nanostructured WO3 Thin Films Grown by Spray Deposition.

The present communication reports on the effect of the sprayed solution volume variation (as a thickness variation element) on the detailed Raman spectroscopy for WO3 thin films with different thicknesses grown from precursor solutions with two different concentrations. Walls-like structured monoclinic WO3 thin films were obtained by the spray deposition method for further integration in gas sensors. A detailed analysis of the two series of samples shows that the increase in thickness strongly affects the films' morphology, while their crystalline structure is only slightly affected. The Raman analysis contributes to refining the structural feature clarifications. It was observed that, for 0.05 M precursor concentration series, thinner films (lower volume) show less intense peaks, indicating more defects and lower crystallinity, while thicker films (higher volume) exhibit sharper and more intense peaks, suggesting improved crystallinity and structural order. For higher precursor concentration 0.1 M series, films at higher precursor concentrations show overall more intense and sharper peaks across all thicknesses, indicating higher crystallinity and fewer defects. Differences in peak intensity and presence reflect variations in film morphology and structural properties due to increased precursor concentration. Further studies are ongoing.

Hybrid nanomaterial-based indirect electrochemical sensing of glyphosate in surface water: a promising approach for environmental monitoring.

Glyphosate (GLY), a widely utilized pesticide, poses a significant threat to human health even at minute concentrations. In this study, we propose an innovative electrochemical sensor for the indirect detection of GLY in surface water samples. The sensor incorporates a nanohybrid material composed of multi-layer graphene decorated with gold nanoparticles (AuNPs), synthesized in a single-step electrochemical process. To ensure portability and on-site measurements, the sensor is developed on a screen-printed electrode, chosen for its integration and miniaturization capabilities. The proposed sensor demonstrates remarkable sensitivity and selectivity for GLY detection in surface water samples, with an exceptional limit of detection (LOD) of 0.03 parts per billion (ppb) in both buffer and surface water matrices. Moreover, it exhibits a remarkably high sensitivity of 0.15 µA ppb-1. This electrochemical sensor offers a promising approach for accurate GLY monitoring, addressing the urgent need for reliable pesticide detection in environmental samples. The proposed sensor showed high selectivity towards GLY, when analysed in the presence of other pesticides such as phosmet, chlorpyrifos and glufosinate-ammonium. The recovery percentages of GLY from spiked surface water samples were between 93.8 and 98.9%. The study's broader implications extend to revolutionizing the way environmental chemistry addresses pesticide contamination, water quality assessment, and sustainable management of environmental pollutants. By pushing the boundaries of detection capabilities and offering practical solutions, this research contributes to the advancement of knowledge and practices that are essential for preserving and protecting our environment.

Functional Enhancement and Characterization of an Electrophysiological Mapping Electrode Probe with Carbonic, Directional Macrocontacts.

Electrophysiological mapping (EM) using acute electrode probes is a common procedure performed during functional neurosurgery. Due to their constructive specificities, the EM probes are lagging in innovative enhancements. This work addressed complementing a clinically employed EM probe with carbonic and circumferentially segmented macrocontacts that are operable both for neurophysiological sensing ("recording") of local field potentials (LFP) and for test stimulation. This paper illustrates in-depth the development that is based on the direct writing of functional materials. The unconventional fabrication processes were optimized on planar geometry and then transferred to the cylindrically thin probe body. We report and discuss the constructive concept and architecture of the probe, characteristics of the electrochemical interface deduced from voltammetry and chronopotentiometry, and the results of in vitro and in vivo recording and pulse stimulation tests. Two- and three-directional macrocontacts were added on probes having shanks of 550 and 770 µm diameters and 10-23 cm lengths. The graphitic material presents a ~2.7 V wide, almost symmetric water electrolysis window, and an ultra-capacitive charge transfer. When tested with clinically relevant 150 µs biphasic current pulses, the interfacial polarization stayed safely away from the water window for pulse amplitudes up to 9 mA (135 µC/cm2). The in vivo experiments on adult rat models confirmed the high-quality sensing of LFPs. Additionally, the in vivo-prevailing increase in the electrode impedance and overpotential are discussed and modeled by an ionic mobility-reducing spongiform structure; this restricted diffusion model gives new applicative insight into the in vivo-uprisen stimulation overpotential.

Comparative Study of Graphene Nanoplatelets and Multiwall Carbon Nanotubes-Polypropylene Composite Materials for Electromagnetic Shielding.

Graphene nanoplatelets (GNPs) and multiwall carbon nanotubes (CNTs)-polypropylene (PP) composite materials for electromagnetic interference (EMI) shielding applications were fabricated as 1 mm thick panels and their properties were studied. Structural and morphologic characterization indicated that the obtained composite materials are not simple physical mixtures of these components but new materials with particular properties, the filler concentration and nature affecting the nanomaterials' structure and their conductivity. In the case of GNPs, their characteristics have a dramatic effect of their functionality, since they can lead to composites with lower conductivity and less effective EMI shielding. Regarding CNTs-PP composite panels, these were found to exhibit excellent EMI attenuation of more than 40 dB, for 10% CNTs concentration. The development of PP-based composite materials with added value and particular functionality (i.e., electrical conductivity and EMI shielding) is highly significant since PP is one of the most used polymers, the best for injection molding, and virtually infinitely recyclable.

Carbon Allotropes-Based Paints and Their Composite Coatings for Electromagnetic Shielding Applications.

The present manuscript reports on optimized formulations of alcohol-based conductive paints for electromagnetic interference shielding (EMI), which can ensure compatibility and reduce the visibility of electronic equipment, as a continuation of our previous work in this field, which examined water-based formulations for other applications. Graphite, carbon black, graphene, Fe3O4, Fe ore, and PEDOT:PSS in various ratios and combinations were employed in an alcohol base for developing homogeneous paint-like fluid mixtures that could be easily applied to surfaces with a paintbrush, leading to homogeneous, uniform, opaque layers, drying fast in the air at room temperature; these layers had a reasonably good electrical conductivity and, subsequently, an efficient EMI-shielding performance. Uniform, homogeneous and conductive layers with a thickness of over 1 mm without exfoliations and cracking were prepared with the developed paints, offering an attenuation of up to 50 dB of incoming GHz electromagnetic radiation. The structural and morphological characteristics of the paints, which were studied in detail, indicated that these are not simple physical mixtures of the ingredients but new composite materials. Finally, mechano-climatic and environmental tests on the coatings demonstrated their quality, since temperature, humidity and vibration stressors did not affect them; this result proves that these coatings are suitable for commercial products.

3D Printed Metal Oxide-Polymer Composite Materials for Antifouling Applications.

Current technology to prevent biofouling usually relies on the use of toxic, biocide-containing materials, which can become a serious threat to marine ecosystems, affecting both targeted and nontargeted organisms. Therefore, the development of broad-spectrum, less toxic antifouling materials is a challenge for researchers; such materials would be quite important in applications like aquaculture. In this respect, surface chemistry, physical properties, durability and attachment scheme can play a vital role in the performance of the materials. In this work, acrylonitrile butadiene styrene (ABS)/micro ZnO or nano ZnO composite lattices with different metal oxide contents were developed using 3D printing. Their antifouling behavior was examined with respect to aquaculture applications by monitoring growth on them of the diatoms Navicula sp. and the monocellular algae Chlorella sp. with image analysis techniques. As shown, the presence of metal oxides in the composite materials can bring about antifouling ability at particular concentrations. The present study showed promising results, but further improvements are needed.

Novel Water-Based Paints for Composite Materials Used in Electromagnetic Shielding Applications.

The development of materials offering electromagnetic interference (EMI) shielding is of significant consideration, since this can help in expanding the lifetime of devices, electromagnetic compatibility, as well as the protection of biological systems. Conductive paints used widely today in electromagnetic interference (EMI) shielding applications are often based on organic solvents that can create safety issues due to the subsequent environment problems. This paper concerned the development of eco-friendly conductive water-based paints for use in EMI-shielding applications. Graphene nanoplatelets, polyaniline emeraldine (PANI) doped with poly(styrene sulfonic acid) (PSS) or HCl or HBr and poly(3,4-ethylenedioxythiophene) poly(styrene sulfonic acid) (PEDOT:PSS) in various ratios were employed in a water base for developing the paints. The target was to develop homogeneous water-based paint-like fluid mixtures easily applied onto surfaces using a paint brush, leading in homogeneous, uniform, opaque layers, draying fast in air at room temperature, and having quite good electrical conductivity that can offer efficient EMI-shielding performance. The results of this parametric trial indicated the optimum compositions leading in paints with optimized properties that can result in uniform, homogeneous, and conductive layers up to a thickness of over 500 µm without deformation and cracking, offering attenuation of up to 60 dBs of incoming GHz electromagnetic radiation. In addition, the structural and morphological characteristics of these paints were studied in detail.

Ternary Nanocomposites Based on Oxidized Carbon Nanohorns as Sensing Layers for Room Temperature Resistive Humidity Sensing.

This paper presents the relative humidity (RH) sensing response of a resistive sensor employing sensing layers based on a ternary nanocomposite comprising graphene oxide-oxidized carbon nanohorns-polyvinylpyrrolidone (GO-CNHox-PVP), at 1/1/1, 1/2/1, and 1/3/1 w/w/w mass ratios. The sensing structure is composed of a silicon substrate, a SiO2 layer, and interdigitated transducers (IDT) electrodes, on which the sensing layer is deposited via the drop-casting method. The morphology and the composition of the sensing layers are investigated through scanning electron microscopy (SEM) and RAMAN spectroscopy. The RH sensing capability of each carbonaceous nanocomposite-based thin film was analyzed by applying a current between the two electrodes and by measuring the voltage difference when varying the RH from 0% to 100% in humid nitrogen. The sensors have a room temperature response comparable to that of a commercial humidity sensor and are characterized by a rapid response, excellent linearity, good sensitivity, and recovery time. The manufactured sensing devices' transfer functions were established, and we extracted the response and recovery times. While the structures with GO/CNHox/PVP at 1/1/1 ratio (w/w/w) had the best performance in terms of relative sensibility, response time, and recovery time, the sensors employing the GO/CNHox/PVP nanocomposite at the 1/2/1 ratio (w/w/w) had the best linearity. Moreover, the ternary mixture proved to have much better sensing properties compared to CNHox and CNHox-PVP-based sensing layers in terms of sensitivity and linearity. Each component of the ternary nanocomposites' functional role is explained based on their physical and chemical properties. We analyzed the potential mechanism associated with the sensors' response; among these, the effect of the p-type semiconductor behavior of CNHox and GO, correlated with swelling of the PVP, was dominant and led to increased resistance of the sensing layer.

A New Hybrid Sensitive PANI/SWCNT/Ferrocene-Based Layer for a Wearable CO Sensor.

Developing a sensing layer with high electroactive properties is an important aspect for proper functionality of a wearable sensor. The polymeric nanocomposite material obtained by a simple electropolymerization on gold interdigitated electrodes (IDEs) can be optimized to have suitable conductive properties to be used with direct current (DC) measurements. A new layer based on polyaniline:poly(4-styrenesulfonate) (PANI:PSS)/single-walled carbon nanotubes (SWCNT)/ferrocene (Fc) was electrosynthesized and deposed on interdigital transducers (IDT) and was characterized in detail using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoemission spectroscopy (XPS), and X-ray diffraction (XRD). The sensor characteristics of the material towards carbon monoxide (CO) in the concentration range of 10-300 ppm were examined, showing a minimal relative humidity interference of only 1% and an increase of sensitivity with the increase of CO concentration. Humidity interference could be controlled by the number of CV cycles when a compact layer was formed and the addition of Fc played an important role in the decrease of humidity. The results for CO detection can be substantially improved by optimizing the number of deposition cycles and enhancing the Fc concentration. The material was developed for selective detection of CO in real environmental conditions and shows good potential for use in a wearable sensor.

Electrical Percolation Threshold and Size Effects in Polyvinylpyrrolidone-Oxidized Single-Wall Carbon Nanohorn Nanocomposite: The Impact for Relative Humidity Resistive Sensors Design.

This paper reports, for the first time, on the electrical percolation threshold in oxidized carbon nanohorns (CNHox)-polyvinylpyrrolidone (PVP) films. We demonstrate-starting from the design and synthesis of the layers-how these films can be used as sensing layers for resistive relative humidity sensors. The morphology and the composition of the sensing layers are investigated through Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and RAMAN spectroscopy. For establishing the electrical percolation thresholds of CNHox in PVP, these nanocomposite thin films were deposited on interdigitated transducer (IDT) dual-comb structures. The IDTs were processed both on a rigid Si/SiO2 substrate with a spacing of 10 µm between metal digits, and a flexible substrate (polyimide) with a spacing of 100 µm. The percolation thresholds of CNHox in the PVP matrix were equal to (0.05-0.1) wt% and 3.5 wt% when performed on 10 µm-IDT and 100 µm-IDT, respectively. The latter value agreed well with the percolation threshold value of about 4 wt% predicted by the aspect ratio of CNHox. In contrast, the former value was more than an order of magnitude lower than expected. We explained the percolation threshold value of (0.05-0.1) wt% by the increased probability of forming continuous conductive paths at much lower CNHox concentrations when the gap between electrodes is below a specific limit. The change in the nanocomposite's longitudinal Young modulus, as a function of the concentration of oxidized carbon nanohorns in the polymer matrix, is also evaluated. Based on these results, we identified a new parameter (i.e., the inter-electrode spacing) affecting the electrical percolation threshold in micro-nano electronic devices. The electrical percolation threshold's critical role in the resistive relative-humidity sensors' design and functioning is clearly emphasized.

Organic-Inorganic Ternary Nanohybrids of Single-Walled Carbon Nanohorns for Room Temperature Chemiresistive Ethanol Detection.

Organic-inorganic ternary nanohybrids consisting of oxidized-single walled carbon nanohorns-SnO2-polyvinylpyrrolidone (ox-SWCNH/SnO2/PVP) with stoichiometry 1/1/1 and 2/1/1 and ox-SWCNH/ZnO/PVP = 5/2/1 and 5/3/2 (all mass ratios) were synthesized and characterized as sensing films of chemiresistive test structures for ethanol vapor detection in dry air, in the range from 0 up to 50 mg/L. All the sensing films had an ox-SWCNH concentration in the range of 33.3-62.5 wt%. A comparison between the transfer functions and the response and recovery times of these sensing devices has shown that the structures with ox-SWCNH/SnO2/PVP = 1/1/1 have the highest relative sensitivities of 0.0022 (mg/L)-1, while the devices with ox-SWCNH/SnO2/PVP = 2/1/1 have the lowest response time (15 s) and recovery time (50 s) for a room temperature operation, proving the key role of carbonic material in shaping the static and dynamic performance of the sensor. These response and recovery times are lower than those of "heated" commercial sensors. The sensing mechanism is explained in terms of the overall response of a p-type semiconductor, where ox-SWCNH percolated between electrodes of the sensor, shunting the heterojunctions made between n-type SnO2 or ZnO and p-type ox-SWCNH. The hard-soft acid-base (HSAB) principle supports this mechanism. The low power consumption of these devices, below 2 mW, and the sensing performances at room temperature may open new avenues towards ethanol sensors for passive samplers of environment monitoring, alcohol test portable instruments and wireless network sensors for Internet of Things applications.

Annealing Effect on the Properties of Electrochromic V2O5 Thin Films Grown by Spray Deposition Technique.

Nanostructured electrochromic V2O5 thin films were prepared using spray pyrolysis technique growth at a temperature of 250 °C using air-carrier spray deposition, starting from ammonium metavanadate precursor in water, followed by annealing at 400 °C in O2 atmosphere for 2 h. The V2O5 films were characterized by X-ray diffraction, scanning electron microscopy, and Raman spectroscopy, and their electrochromic behavior was studied using optical spectroscopy and cyclic voltammetry in both the as-deposited and postannealing case. The studies showed that the simple, cost -effective, suitable for large area deposition method used can lead to an interesting surface structuring with large active surface properties suitable for electrochromic applications. Further studies for growth optimization and improvements of films properties and stability are to be performed.

Effect of Graphene Nanoplatelets on the Structure, the Morphology, and the Dielectric Behavior of Low-Density Polyethylene Nanocomposites.

The incorporation of graphene nanoplatelets (GnPs) within a polymer matrix can play an important role in the physical properties and the functionality of the composite material. Composites consisting of low-density polyethylene (LDPE) and GnPs of different concentrations were developed by mixing GnPs with a molten form of the polymeric matrix. The effect of the GnPs content on the morphological, structural, and electrical properties of the composites were investigated. As shown, graphene presence and its concentration significantly modified the polymer matrix properties, a behavior that can be employed for tailoring its applicability in electrical applications. It was found that the increase of the graphene platelets concentration seems to promote the formation of graphene agglomerates, air gaps, and inhomogeneities, while higher dielectric constant/lower dielectric losses can be achieved.

Electrochromic Performance of V2O5 Thin Films Grown by Spray Pyrolysis.

A new approach regarding the development of nanostructured V2O5 electrochromic thin films at low temperature (250 °C), using air-carrier spray deposition and ammonium metavanadate in water as precursor is presented. The obtained V2O5 films were characterized by X-ray diffraction, scanning electron microscopy and Raman spectroscopy, while their electrochromic response was studied using UV-vis absorption spectroscopy and cyclic voltammetry. The study showed that this simple, cost effective, suitable for large area deposition method can lead to V2O5 films with large active surface for electrochromic applications.

Dataset on large area nano-crystalline graphite film (NCG) grown on SiO2 using plasma-enhanced chemical vapour deposition.

A Si wafer coated with a low temperature oxide (LTO) was used as substrate (Si/SiO2) during the deposition of a thick nano-crystalline graphite (NCG) film by means of plasma-enhanced chemical vapour deposition (PECVD) procedure. The process parameters, the atomic force (AFM) and scanning electron (SEM) micrographs, Raman spectrum and X-ray diffraction (XRD) pattern are herein illustrated. The as deposited NCG film was electrochemically pretreated (3 mA applied current, during 240 s, in 10 mM phosphate buffer saline (PBS) solution containing 0.1 M KCl, pH 7) and thereafter used as electrode for sensing the caffeic acid content in lyophilised berries and dried chokeberries in "Nano-crystalline graphite film on SiO2: Electrochemistry and electro-analytical application" [1].

Tunable photoluminescence from interconnected graphene network with potential to enhance the efficiency of a hybrid Si nanowire solar cell.

An interconnected graphene network (IGN) structure with excellent photoluminescence (PL) properties was synthesized using a one-pot microwave-assisted hydrothermal carbonization route. The material exhibited intense and excitation-wavelength dependent PL emission located mainly in the UV-blue light range (300-450 nm). The result demonstrates that graphene networks could also be included in the emerging class of tunable PL carbon nanomaterials. Furthermore, we have taken a first step towards their incorporation into solar cell devices by fabricating IGN/p-SiNWs radial heterojunctions using the versatile potentiostatic electrodeposition technique. The IGN modified p-SiNW solar cell showed the best performance with an overall enhancement of power conversion efficiency of 7.5 times higher than the reference cell. We emphasize that the structural and electronic characteristics of the as-prepared IGN combined with tapering effects are directly responsible for the tripled short circuit current density and 9% improvement of open circuit voltage with respect to the reference cell. Finally, we have demonstrated that the IGN successfully passivated the Si nanowires' surface using intensity modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS). These promising findings indicate that further IGN exploitation may help to gain efficiency in future energy conversion applications.