•A flexible graphene-based platform for sensitive and selective non-enzymatic detection of H2O2.•Fully integration and customization with easy manufacturing process using laser irradiation.•A ...suitable transducer for migration of electrochemical sensors into areas where flexibility is required.
Here, we demonstrate the detection of H2O2 with a novel, flexible and non-enzymatic electrochemical sensor based on a laser scribed graphene electrode decorated with silver nanoparticles(LSG-Ag). This low-cost technique based on a DVD laser, allowed the direct manufacturing and reduction of graphene oxide into an electrochemical transducer with conductive, lightweight, reduced and flexible characteristics. The LSG-Ag sensor showed a high catalytic response towards H2O2 reduction at -0.5 V with a fast amperometric response of only 3 s. The sensor exhibited a wide linear range from 0.1 to 10 mM (R2 = 0.9982), a low LOD of 7.9 μM with high repeatability of 3% R.S.D. and reproducibility of 4.5% R.S.D. In addition, the LSG-Ag retained its operational characteristics after continuous bending with a loss of current of only 13%. Considering the need of progression of electrochemical systems into trending areas where flexibility is required, the laser-induced sensors can provide a suitable platform for flexible, reliable, sensitive and selective detection.
Herein, a methodology is employed based on the Flory-Rehner equation for estimating the Flory-Huggins interaction parameter (χ
*) of crosslinked elastomer blends. For this purpose, binary elastomer ...blends containing polybutadiene rubber (BR), styrene-butadiene rubber (SBR) and nitrile-butadiene rubber (NBR), were prepared in a mixing chamber at a temperature below the activation of the crosslinking agent. Swelling tests with benzene were employed to determine the crosslinked fraction, finding that after 20 min of thermal annealing, the BR and NBR were almost completely crosslinked, while the SBR only reached 60%. Additionally, the BR-SBR blend increased by 2-3 times its volume than its pure components; this could be explained based on the crosslink density. From the mechanical tests, a negative deviation from the rule of mixtures was observed, which suggested that the crosslinking was preferably carried out in the phases and not at the interface. Furthermore, tensile tests and swelling fraction (ϕ
) results were employed to determine the average molecular weight between two crosslinking points (M
), and subsequently χ
*. Calculated χ
* values were slightly higher than those reported in the literature. The calculated thermodynamic parameters for the blends showed positive ΔG
values and endothermic behavior, suggesting their immiscible nature.
•Fabrication of active SERS composites based on laser reduced graphene as template.•Electrodeposited dendritic structures over flexible graphene structure.•Detection of R6G probe at nanomolar ...concentrations.
The current trends in flexible devices has drawn considerable attention to the creation of bendable SERS substrates. In this work, we present a flexible SERS substrate developed from laser scribed graphene (LSG) and silver dendrites (AgD), combining the inherent chemical enhancement of graphene and the electromagnetic amplification of magnetic nanostructures within one platform. The laser irradiation allowed the controlled reduction of graphene oxide to create a conductive, lightweight and flexible template for growing of AgD by electrodeposition. The LSG@AgD composites were optimized varying electrodeposition cycles, which drastically affected the performance. The optimal synergistic effects of both materials were achieved after 30 cycles, allowing a fast measurement of R6G probe down to nanomolar levels and preserving the detection even after continuous bending.
Molybdenum trioxide (MoO
3
) has been studied by four thermal analysis techniques. The as-synthesized material has hexagonal structure (h-MoO
3
). The phase change in the material studied using four ...thermal analysis techniques: thermogravimetric analysis, differential scanning calorimetry (DSC), thermomechanical analysis, and dynamic mechanical analysis. Crystallography phase transformation of h-MoO
3
was found between 675 and 701 K by these techniques. DSC technique provided the highest detection sensitivity at about 690 K since the metastable monoclinic phase (β-MoO
3
) transformation could be observed before reaching the stable orthorhombic (α-MoO
3
) phase. The crystallographic phases of particles and morphologies were confirmed by X-ray diffraction and scanning electron microscopy techniques. The h-MoO
3
was proposed as a standard sample to validate the operations of the thermal analysis instruments.
Additive manufacturing (AM), also known as 3D printing, has revolutionized the production of complex geometric structures across various industries. This study presents an innovative approach by ...integrating zinc carbonate basic (ZCB) precursor with polylactic acid (PLA) to develop composite filaments for fused deposition modeling (FDM) 3D printers. The resulting filaments undergo surface transformation into zinc oxide (ZnO) through high-power laser irradiation. Thermal analysis (TGA-DSC) and Fourier-transform infrared spectroscopy (FTIR) were used to confirm the decomposition of ZCB (ZnCO₃₂·Zn(OH)₂₃) into ZnO during the thermal decomposition stages. The study successfully extruded a composite filament containing 10% of ZCB, which worked adequately in 3D printing. The printed parts were analyzed through tensile tests (based on ASTM D638-5 standard), showing a notable difference in mechanical behavior between the commercial filament PLA and the composite filament (PLAC10). Laser irradiation of these samples facilitated a targeted conversion to ZnO, verified through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The integration of zinc oxide within the printed structures enhances structural stability and provides surfaces enriched with ZnO, a metal oxide with widely reported applications. Furthermore, an irradiated 3D-printed sample demonstrated chemo-resistive properties upon carbon monoxide (CO) exposure, underlining its potential as a gas sensor and confirming its semiconductor nature. This approach provides a cost-effective and efficient way to develop innovative devices with integrated functional materials.
Molybdenum trioxide (MoO.sub.3) has been studied by four thermal analysis techniques. The as-synthesized material has hexagonal structure (h-MoO.sub.3). The phase change in the material studied using ...four thermal analysis techniques: thermogravimetric analysis, differential scanning calorimetry (DSC), thermomechanical analysis, and dynamic mechanical analysis. Crystallography phase transformation of h-MoO.sub.3 was found between 675 and 701 K by these techniques. DSC technique provided the highest detection sensitivity at about 690 K since the metastable monoclinic phase (beta-MoO.sub.3) transformation could be observed before reaching the stable orthorhombic (alpha-MoO.sub.3) phase. The crystallographic phases of particles and morphologies were confirmed by X-ray diffraction and scanning electron microscopy techniques. The h-MoO.sub.3 was proposed as a standard sample to validate the operations of the thermal analysis instruments.
This research focused on the development of biomaterials based on cassava starch and corn starch and on the effect of the incorporation of polycaprolactone (PCL) on the thermal and thermomechanical ...properties of the blends. The results indicated partial compatibility in the blends, especially with cassava starch at a content of 20 wt% as reflected by the maintenance of tensile strength and elongation. In addition, the changes in the crystal quality of PCL and the displacement of the absorption bands of the carbonyl groups of PCL in the infrared (989–1000 cm−1), attributed to the formation of hydrogen bonds between these groups and the hydroxyl groups of starches, were also associated with compatibility. It was observed that the crystallinity of PLC in the presence of cassava and corn starch was 38% and 62%, respectively; a crystallinity greater than that of PCL was related to an improved nucleation at the interface. Based on these properties, the blends are expected to be functional for the manufacture of short-term use products by conventional thermoplastic processing methods.
Glucose measurement is a fundamental tool in the daily care of Diabetes Mellitus (DM) patients and healthcare professionals. While there is an established market for glucose sensors, the rising ...number of DM cases has promoted intensive research to provide accurate systems for glucose monitoring. Polyaniline (PAni) is a conductive polymer with a linear conjugated backbone with sequences of single C-C and double C=C bonds. This unique structure produces attractive features for the design of sensing systems such as conductivity, biocompatibility, environmental stability, tunable electrochemical properties, and antibacterial activity. PAni-based glucose sensors (PBGS) were actively developed in past years, using either enzymatic or non-enzymatic principles. In these devices, PAni played roles as a conductive material for electron transfer, biocompatible matrix for enzymatic immobilization, or sensitive layer for detection. In this review, we covered the development of PBGS from 2015 to the present, and it is not even exhaustive; it provides an overview of advances and achievements for enzymatic and non-enzymatic PBGB PBGS for self-monitoring and continuous blood glucose monitoring. Additionally, the limitations of PBGB PBGS to advance into robust and stable technology and the challenges associated with their implementation are presented and discussed.
Due to its relatively simple structure, low-density polyethylene (LDPE) can be considered as a model polymer for the study of its properties. Herein, the effect of processing variables on the ...microstructure and crystallinity of injection-molded LDPE specimens was quantitatively determined. The polymer was injected at different temperature conditions in the barrel and the mold. The specimens were characterized by scanning electron microscopy and X-ray diffraction. With the data obtained, an analysis of variance (ANOVA) was carried out, and response surface graphs (SRP) were constructed to quantify and to observe the behavior of the processing variables, respectively. Different models were obtained to predict the effect of the experimental factors on the response variables. The results showed that the interaction of the two temperatures has the greatest effect on the size of the spherulite, while the temperature of the mold affects the crystallinity. The SRP showed different behaviors: for the spherulite, the size increases with the mold temperature, while for the crystallinity, higher values were observed at an intermediate mold temperature and a low melt temperature. The results presented herein are valuable for setting empirical relations between the microstructure, crystallinity, and the molding conditions of LDPE.
This study aimed to obtain a second-generation snack by extrusion from the by-product of rice milling enriched with amaranth. The raw material used was amaranth flour (AF), rice starch (NS) and ...modified rice starch (MS), which were evaluated by the analysis of substitution degree (SD), differential scanning calorimetry (DSC), viscosity (RVA), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The snacks were expanded by extrusion and microwave oven, as a reference method. The samples were evaluated in hardness (D), expansion index (EI), apparent density (DAP), and protein content (P). Afterward, the optimized samples were evaluated by scanning electron microscopy (SEM) and resistant starch (RS). During the thermal characterization, a clear trend in the decrement in gelatinization temperatures was observed (78.35 to 63.90 °C in NS and MS respectively). The curves obtained in RVA analyses showed typical behavior of native (6.35 Pa.s) and extruded starches (2.88 Pa.s), with a significant decrease in viscosity peak. Through the analysis of FT-IR, the introduction of the functional acetyl group (stretching at a wavelength of 1735 cm
) was corroborated. Snack samples results showed a maximum hardness in MS, with a value of 121 N, and the NS (100%) presented the highest EI value (1.41). The lowest DAP values were obtained for the MS (0.48 g/cm
, 100%) and AF (0.49 g/cm
, 100%) samples. P increased to a higher concentration of AF. In the optimum formulation, the SEM image showed that the expanded microwave sample increased the porosity and obtained an RS value of 8.2%. The formulation obtained in the present study presents high characteristics to be used in the development of a healthy snack.
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