Improvised Centrifugal Spinning for the Production of Polystyrene Microfibers From Waste Expanded Polystyrene Foam and Its Potential Application for Oil Adsorption

A straightforward approach to recycle waste expanded polystyrene (EPS) foam to produce polystyrene (PS) microfibers using the improvised centrifugal spinning technique is demonstrated in this work. A typical benchtop centrifuge was improvised and used as a centrifugal spinning device. The obtained PS microfibers were characterized for their potential application for oil adsorption. Fourier transform infrared spectroscopy results revealed similarity on the transmission bands of EPS foam and PS microfibers suggesting the preservation of the EPS foam’s chemical composition after the centrifugal spinning process. Scanning electron microscopy displayed well-defined fibers with an average diameter of 3.14 ± 0.59 μm. At the same time, energy dispersive X-ray spectroscopy revealed the presence of carbon and oxygen as the primary components of the fibers. Contact angle (θCA) measurements showed the more enhanced hydrophobicity of the PS microfiber (θCA = 100.2 ± 1.3°) compared to the untreated EPS foam (θCA = 92.9 ± 3.5°). The PS microfiber also displayed better oleophilicity compared to EPS foam. Finally, the fabricated PS microfibers demonstrated promising potential for oil removal in water with a calculated sorption capacity value of about 15.5 g/g even at a very short contact time. The fabricated PS fiber from the waste EPS foam may provide valuable insights into the valorization of polymeric waste materials for environmental and other related applications

Single-Dip Colorimetric Detection of Cyanide Using Paper-Based Analytic Device Based on Immobilized Silver Nanoparticles

The need to monitor the presence of cyanide (CN−) in water is necessary to minimize the risks to aquatic ecosystems and human health. In this paper; a paper-based analytical device (PAD) was fabricated by immobilizing silver nanoparticles (AgNPs) on filter paper (FP) for the semi-quantitative colorimetric detection of CN− in water. The average diameter of the synthesized AgNPs was estimated to be around 26.23 ± 8.37 nm; with a characteristic optical absorption peak around 420 nm. Scanning electron microscopy and energy-dispersive X-ray spectroscopy results confirmed the successful immobilization of AgNPs on the filter paper via direct immersion technique. The potential of the fabricated FP-AgNPs PAD as a colorimetric sensor for CN− was evaluated using water samples contaminated with various ions and CN− concentration. Here; a color change from yellow to colorless was instantly observed as the FP-AgNPs PAD was exposed to water samples containing CN−. Interestingly; no color change was observed for samples exposed to other analytes suggesting the good selectivity of the FP-AgNPs PAD. Ultraviolet–Visible spectroscopy results and digital image analysis revealed that the fabricated sensor can detect CN− with concentration down to 1.0 ppm. The colorimetric response was also obtained for real water samples spiked with CN−. The results stipulated in this work offer baseline information that can be used in developing highly selective and sensitive digital sensing devices for affordable; accessible; and fast water contaminant monitoring and other related applications

Detecting mercury ions in water using a low-cost colorimetric sensor derived from immobilized silver nanoparticles on a paper substrate

The exceptional and specific reactivity of mercury ions (Hg2+) toward plasmonic silver nanoparticles (AgNPs) in aqueous media has motivated the need to develop innovative, low-cost, portable, and robust sensors to help address the detrimental effects of heavy metal contamination particularly in rural communities. In this paper, we present the plasmonic and colorimetric sensing of Hg2+ using a paper-based sensing material derived from thiamine-functionalized (ThAgNPs) that were immobilized on a commercial filter paper. Plasmonic AgNPs with a surface plasmon resonance peak at 420 nm and a size of about 21.3 nm were synthesized by a chemical reduction technique. Fourier transform infrared spectroscopy revealed the characteristic functional groups of thiamine in the spectra of AgNPs, thereby confirming the functionalization of AgNPs. The successful integration of ThAgNPs onto the Whatman filter paper (WFP) matrix was confirmed by the UV–vis and SEM-EDX results. An evident color change from yellowish to white was manifested by the fabricated WFP-ThAgNP sensor in the presence of Hg2+ with an appreciable detection of up to 0.5 µM using the naked eye. The colorimetric response of the sensor was also found to be selective towards Hg2+ after testing with different metal ions. Moreover, the response was consistent for tap, and creek water samples spiked with Hg2+. The results of this work provide a promising baseline technology for the development of an affordable, fast, portable, and reliable sensor that can be used for on-site detection and monitoring of Hg2+ levels in the water

Functionalized Silver Nanoparticle-Decorated Paper Sensor for Rapid Colorimetric Detection of Copper Ions in Water

Copper contamination to water bodies is an environmental concern of significant risk due to its harmful effect on aquatic life forms and human beings. Herein, a paper-based colorimetric sensor was fabricated by immobilizing polyethyleneimine-capped silver nanoparticles (PEI-AgNPs) on commercial filter paper. The sensitivity and selectivity of the paper-based sensor\u27s colorimetric response to copper ions in water were investigated. PEI-AgNPs with an average diameter of 12.66 ± 4.07 nm were successfully immobilized on the filter paper by the simple dipping technique, as evidenced by the scanning electron microscopy with energy-dispersive x-ray result. A color change from pale yellow to dark yellow green was noted after exposing the paper sensor in a water sample with copper ions. This colorimetric response was exclusively observed for copper ions only, suggesting the selectivity of the paper sensor towards copper ions. Moreover, ultraviolet–visible spectroscopy results revealed that the detection limit of the paper sensor was observed to about 1.0 ppm. Meanwhile, color analysis on the sensor\u27s digital images revealed the linear response of the sensor with decreasing copper ion concentration down to 1.0 ppm. The selectivity of the sensor was also observed by the color intensity profile of the sensor. This work presents promising results that can be utilized as a reference for developing affordable, fast, portable, and reliable sensing devices for on-site water quality monitoring and other applications

Preparation of Spin-Coated Poly(vinyl alcohol)/ chitosan/ Gold Nanoparticles Composite and Its Potential for Colorimetric Detection of Cyanide in Water

The rampant use of cyanide in mining activities has posed a substantial hazard to aquatic ecosystems and human health. Herein, a composite film of poly(vinyl alcohol)/chitosan (PVA/CS) with gold nanoparticles was synthesized as a potential colorimetric sensor for cyanide ions detection in water. The utilized AuNPs with a mean diameter of 14.32±3.49 nm were synthesized by chemical reduction using polyethyleneimine. Ultraviolet-visible spectroscopy revealed the characteristic peak of AuNPs at around 530 nm in the spectrum of PVA/CS/AuNP film, while SEM microscopy revealed the integration AuNPs across the polymer substrate. A color change from red to colorless was observed on the composite film after the addition of water samples with cyanide ions with a visual detection limit between 0.1-1 ppm. The sensor also exhibited good selectivity towards cyanide against the tested water samples containing various metal ions. This study reveals the potential of the fabricated PVA/CS/AuNP composite film as a simple, affordable, and environmentally benign material for on-site detection of cyanide in water and other related application