Search

This work investigates the influence of methylhexahydrophthalic anhydride (MHHPA) on the properties of phthalic anhydride-based unsaturated polyester resin (PA-based UPR) when PA is replaced by MHHPA with different PA/MHHPA mole ratios, ranging from 100/0 to 0/100. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) are used to study the chemical structure, curing process and mechanical properties of the resins, showing the successful incorporation of MHHPA into the structure of UPRs with superior properties, compare to PA-based UPRs. In particular, the addition of MHHPA significantly lowers the acidity by up to 28% and promotes the curing reaction, reducing the enthalpy of the reaction by 2.5 times, and shortens the curing time by up to 40%. This incorporation also increases the gel content up to 99.9%, thereby increasing the crosslinking between the polyester chains and improving the rigidity of UPRs. In addition, the glass-transition temperature of the polymer increases approximately 78%, which can improve the working temperature of the MHHPA-modified UPRs. The electrical properties of the resins containing MHHPA reveal better insulating performance in comparison with the PA-based UPR. These findings demonstrate great potentials of the MHHPAmodified UPRs for various applications, especially in outdoor environments. KEYWORDS methylhexahydrophthalic anhydride, phthalic anhydride, unsaturated polyester resins, 1 | INTRODUCTION Unsaturated polyester resins (UPRs) are generally linear polymers with ester bonds and unsaturated double bonds, which are generally formed by the condensation reaction of unsaturated diacids and [...]

Multifunctional nanocomposites have received great attention for years; electron transfer (ET) is considered as an explanatory mechanism for enhancement of performance of these nanostructures. The existence of this ET process has been proved in many studies using either experimental or computational approaches. In this study, a ternary nanocomposite system of Ag/TiO2/GO was prepared to evaluate the performance enhancement in two experimental models: a physical model (i.e., surface-enhanced Raman scattering (SERS) sensor) and a chemical one (i.e., catalytic reduction reaction). The metal/semiconductor heterojunction between Ag and TiO2, as well as Ti-O-C bonds, has allowed plasmonic hot electrons to be transferred in the internal structure of the material. An investigation on the role of Ag content on the SERS sensing and catalytic reduction efficiency of Ag/TiO2/GO was performed in both models. Interestingly, they all resulted in the same optimal Ag content of 50 wt%. It was then further discussed to provide a convincing evidence for the plasmon-induced electron transfer phenomena in the Ag/TiO2/GO nanostructure. These findings also suggest a pathway to design and develop high-performance, cost-effective, facile-preparation, and eco-friendly multifunctional nanostructures for detecting and removing contaminants in environment.

Taking advantage of metal–semiconductor junctions, functional nanocomposites have been designed and developed as active substrates for surface-enhanced Raman scattering (SERS) sensing systems. In this work, we prepared three types of nanocomposites based on manganese oxide (MnO2) nanostructures and electrochemically synthesized silver nanoparticles (e-AgNPs), which differed according to the morphologies of MnO2. The SERS performance of MnO2 nanosheet/e-Ag (MnO2-s/e-Ag), MnO2 nanorod/e-Ag (MnO2-r/e-Ag), and MnO2 nanowire/e-Ag (MnO2-w/e-Ag) was then evaluated using tricyclazole (TCZ), a commonly used pesticide, as an analyte. Compared to the others, MnO2-s/e-Ag exhibited the most remarkable SERS enhancement. Thanks to its large surface area and ability to accept/donate the electrons of the semiconductor, MnO2-s acted as a bridge to improve the charge transfer efficiency from e-Ag to TCZ. In addition, the MnO2 content of the nanocomposites was also considered to optimize the SERS sensing performance. With the optimal MnO2 content of 25 wt%, MnO2-s/e-Ag could achieve the best SERS performance, allowing the detection of TCZ at concentrations down to 6 × 10−12 M in standard solutions and 10−11 M in real rice samples. [ABSTRACT FROM AUTHOR]

In this work, we investigated the effect of morphology on the analytical performance of α-Fe2O3 nanostructures-based electrochemical sensors toward chloramphenicol (CAP) antibiotic using three designed morphologies including α-Fe2O3 nano-tube (α-Fe2O3-T), α-Fe2O3 nano-rice (α-Fe2O3-R), and α-Fe2O3 nano-plate (α-Fe2O3-P). Among these morphologies, α-Fe2O3-T displayed an outstanding electrochemical activity owing to the unique hollow structure and large specific surface area. However, due to the small pores size, α-Fe2O3-T showed the high steric hindrance (SD) effect towards an antibiotic with complex molecular structure, as CAP, leading to a significant decrease of their CAP electrochemical sensing performance. The CAP analytical performance of α-Fe2O3-R was highest in investigated morphologies owing to a high density of exposed Fe3+ as well as less SD effect towards CAP molecules. Under optimized conditions, α-Fe2O3-R-based CAP electrochemical sensor reached an electrochemical sensitivity of 0.92 µA µM-1 cm-2 with a LOD of 0.11 µM in the detection range from 2.5-50 µM. In addition, all these α-Fe2O3 nanostructures-based electrochemical sensors had excellent stability and high anti-interference ability for CAP analysis in a complex food matrix, as shrimp sample. This study provides valuable insights into the morphology-dependent sensing properties of α-Fe2O3 nanostructures towards antibiotics, which is helpful to the design of novel α-Fe2O3-based electrochemical nanosensors. [ABSTRACT FROM AUTHOR]

Despite being an excellent surface enhanced Raman scattering (SERS) active material, gold nanoparticles were difficult to be loaded onto the surface of filter paper to fabricate flexible SERS substrates. In this study, electrochemically synthesized gold nanoparticles (e-AuNPs) were deposited on graphene oxide (GO) nanosheets in solution by ultrasonication, resulting in the formation of a GO/Au hybrid material. Thanks to the support of GO, the hybrid material could adhere onto the surface of filter paper, which was immersed into a GO/Au solution for 24 h and dried naturally at room temperature. The paper-based materials were then employed as substrates for a surface enhanced Raman scattering (SERS) sensing platform to detect tricyclazole (TCZ), a widely used pesticide, resulting in better sensitivity compared to the use of paper/Au SERS sensors. With the most optimal GO content of 4%, paper/GO/Au SERS sensors could achieve a limit of detection of 1.32 × 10 -10 M in standard solutions. Furthermore, the filter paper-based SERS sensors also exhibited significant advantages in sample collection in real samples. On one hand, the sensors were dipped into orange juice, allowing TCZ molecules in this real sample to be adsorbed onto their SERS active surface. On the other hand, they were pasted onto cucumber skin to collect the analytes. As a result, the paper/GO/Au SERS sensors could sense TCZ in orange juice and on cucumber skin at concentrations as low as 10 -9 M (∼2 ppb). In addition, a machine learning model was designed and developed, allowing the sensing system to discriminate TCZ from nine other organic compounds and predict the presence of TCZ on cucumber skin at concentrations down to 10 -9 M., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (This journal is © The Royal Society of Chemistry.)

A functional ternary substrate was developed for surface-enhanced Raman scattering (SERS) sensing systems. MnO 2 nanosheets were synthesized by a simple and controllable hydrothermal method, followed by the integration of graphene oxide (GO) nanosheets. Subsequently, MnO 2 /GO nanostructures were decorated with plasmonic Ag nanoparticles (e-AgNPs). The MnO 2 /GO/e-Ag substrate could enhance the SERS sensing signal for organic chemicals without the assistance of chemical bonds between those analytes and the semiconductor within the ternary substrate, which have been proven to promote charge transfer and elevate the SERS enhancement in previous studies. Instead, GO nanosheets acted as a carpet also supporting the MnO 2 nanosheets and e-AgNPs to form a porous structure, allowing the analytes to be well-adsorbed onto the ternary substrate, which improved the sensing performance of the SERS platform, compared to pure e-AgNPs, MnO 2 /e-Ag, and GO/e-Ag alone. The GO content in the nanocomposite was also considered to optimize the SERS substrate. With the most optimal GO content of 0.1 wt%, MnO 2 /GO/e-Ag-based SERS sensors could detect carbaryl, a pesticide, at concentrations as low as 1.11 × 10 -8 M in standard solutions and 10 -7 M in real tap water and cucumber extract., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (This journal is © The Royal Society of Chemistry.)