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Detecting ammonia at low concentrations is crucial in various fields, including environmental monitoring, industrial processes, and healthcare. This study explores the development and performance of an ultra-sensitive ammonia sensor using carboxylic group-functionalized multi-walled carbon nanotubes (f-MWCNTs) overlaid on polyvinyl acetate nanofibers coated on a quartz crystal microbalance (QCM). The sensor demonstrates high responsiveness, with a frequency shift response of over 120 Hz when exposed to 1.5 ppm ammonia, a sensitivity of 23.3 Hz ppm−1 over a concentration range of 1.5–7.5 ppm, and a detection limit of 50 ppb. Additionally, the sensor exhibits a rapid response time of only 14 s, excellent selectivity against other gases, such as acetic acid, formaldehyde, methanol, ethanol, propanol, benzene, toluene, and xylene, and good stability in daily use. These characteristics make the sensor a promising tool for real-time ammonia detection in diverse applications. [ABSTRACT FROM AUTHOR]

Photocatalysis-assisted PVA/TiO2 nanofibers has become a prospective technology for water filtration applications. In line with this application, swelling behavior, photocatalytic activity and reusability are crucial considerations. This work presents the evaluation of swelling behavior and photocatalytic activity of PVA/TiO2 nanofibers in harsh pH environment. By varying pH environment at pH = 1 - 12, we have successfully shown that pH = 7 is the best environment for the PVA/TiO2 nanofibersbased water filtration. On this environment, the nanofibers has 92 % degradability and is able to resist Methylene Blue (MB) solution for up to 5 min. Likewise, it shows excellent reusability over 5 cycles usage. Moreover, the nanofibers is prospective for rapid filtration in harsh pH environment. This work is a step forward toward environmental-friendly water filtration in harsh pH environment. [ABSTRACT FROM AUTHOR]

Nanofiber is a material used as a drug carrier matrix in drug release materials. Its morphology has high porosity and good flexibility, making it suitable for this purpose. The use of nanofiber as a carrier matrix in slow‐release fertilizer (SRF) material is expected to provide a solution for releasing fertilizer into the soil more measurably and efficiently In this study, PVA/Urea/TiO2 nanofibers were fabricated using the electrospinning method. PVA/Urea/TiO2 SRFs were prepared using varying urea mass percentages (10%, 15%, and 20% of PVA mass) and the concentration of titanium dioxide suspension solution (0, 0.2, and 0.4 mL). Every sample was analyzed using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) and tested using contact angle and slow‐release tests. From SEM characterizations, all samples showed the ability to form nanofiber. It was found that the membrane diameter sizes for each sample A, B, C, D, E, and F were 341 ± 5, 309 ± 12, 109 ± 3, 313 ± 10, 109 ± 3, and 158 ± 6 nm, respectively. The FTIR characterizations showed that all the matrix samples successfully contained the nitrogen group, which was found at wave number 1605 cm−1 (NH deformation), 1574 cm−1 (CN stretching), and 3430 cm−1 (NH stretching). The SEM mapping images confirmed the presence of titanium dioxide (green dots). The contact angle test showed that all samples had hydrophilic properties (the contact angle value lower than 90°), and the greatest value of contact angle measurement was 31.08° for sample C/E (sample with the most presence of TiO2 suspension solution 0.4 mL). The sample with the greatest TiO2 suspension concentration (0.4 mL) had the longest urea release time, lasting 8 days. This result indicates the addition of TiO2, can potentially suppress the hydrophilic properties of the PVA membrane. It is found that the addition of TiO2 influenced the membrane's hydrophilicity, consequently increasing the release rate. This study used the Korsmeyer–Peppas mathematical kinetic model to show that diffusion and swelling are release mechanisms for SRF membranes. [ABSTRACT FROM AUTHOR]

Real-time detection of formaldehyde in the atmosphere remains challenging. The available gaseous formaldehyde sensing methods offer limited sensitivity, selectivity, and robustness. We modified a quartz crystal microbalance (QCM) system for selective detection of formaldehyde in air. The QCM surface was functionalized with polyvinyl acetate (PVAc) nanofibers and doped with 2, 4, and 6 wt% aniline to improve the selectivity and sensitivity of the sensor. The chemical content and morphological structure of PVAc nanofibers doped with aniline were confirmed by Fourier-transform infrared (FTIR) spectroscopy, energy-dispersive X-ray (EDX) spectroscopy, and scanning electron microscopy (SEM). The results showed that the modified QCM sensor had a sensitivity of 0.056 Hz ppm−1 with a response and recovery times of 200 s and 90 s, respectively. It gave limits of detection (LOD) and limit of quantification (LOQ) of 28 ppm and 96 ppm, respectively. Moreover, the modified QCM was selective towards formaldehyde compared to the other gases. The current workplace exposure limit (WEL) for formaldehyde is 2 ppm, with a time-weighted average over eight hours. Future work will focus on improving the reported QCM sensor to meet the required LOD for formaldehyde detection in the environment and industrial sites. [ABSTRACT FROM AUTHOR]

Incorporating TiO2 with CNTs and PAN nanofiber structures results in a photocatalytic membrane composite with an attractive response in the visible region. It offers an efficient process without post-treatment separation at the end of the photocatalytic treatment. The composite membranes were fabricated using electrospinning at 7 kV with 10 cm in the distance between needle tip and collector at a flow rate of 1 mL h−1. Polyacrylonitrile (PAN) was used as the polymer matrix. All the as-spun composites exhibited randomly oriented nanofibers. CNT increased the fiber diameters from 324 to 463 nm. The bandgap of TiO2 also shifted from 3.15 to 2.76 eV at the narrowest The color removal kinetics follow the Langmuir-Hinshelwood pseudo-first-order kinetics model with the highest rate constant of 0.0225 min−1 shown by PAN/TiO2/CNT 20%. More than 95% color removal of methylene blue after 100 min irradiation has been achieved using LED lamps of low energy visible light (43.5 W). Such a result is supposed to be the highest employing low energy lamps. [ABSTRACT FROM AUTHOR]

PAN/TiO2/CNT and PAN/TiO2/CNT-PVA composite nanofibrous membranes with photocatalytic activity were successfully synthesized using electrospinning. The effect of CNT concentration and PVA coating on the membrane surface toward the membrane performances was investigated. TiO2 anatase phase was exist on the respective membranes. SEM morphological investigation revealed the random orientation of the nanofibers with beads decorated in each strand. The PAN/TiO2/CNT composite nanofiber membrane exhibited high performance for the removal of cationic organic dye methylene blue (MB) in a cross-flow photocatalytic membrane reactor under low power visible light of LED lamp (14.5 W) and a constant pollutant flow rate of 0.21 L/min. The presence of TiO2/CNT photocatalyst was proven to prolong the lifetime of the photocatalytic membrane and retard membrane fouling to the maximum extent. PAN/TiO2/CNT membrane has displayed 100% MB rejection for the first 8 h of operation. Both, PAN/TiO2/CNT and PAN/TiO2/CNT-PVA maintained their membrane performances and did not show major flux decline even after five recycling uses. The incorporation of TiO2/CNTs on PAN nanofibers has resulted in a durable photocatalytic membrane for the effective removal of dye waste using a cross-flow membrane reactor. [ABSTRACT FROM AUTHOR]

A photocatalytic membrane combining photocatalyst and membrane technology based on polyacrylonitrile (PAN) and TiO2/CNT has been developed. Such combination is to overcome fouling formation on the membrane, thus prolonging the membrane lifetime and enhancing the efficiency on the waste treatment. PAN nanofiber was prepared by electrospinning method. The precursor solution was dissolved PAN and dispersed TiO2/CNT in N, NDimethylformamide (DMF). PAN concentration in the precursor solution was varied at 4.5, 5.5, 6.5, 7.5, and 8.5%. The effect of PAN concentration on the fiber morphology and pore size was discussed. The performance of the resulted membrane on methylene blue (MB) removal was also investigated on a cross-flow system. SEM images of the resulted membrane identified that PAN nanofiber was successfully fabricated with random orientation. The PAN 6.5% showed the highest diffraction intensity of the anatase crystalline phase of TiO2. The additions of CNT and TiO2 lead to the formation of a cluster of beads as confirmed by TEM. Increasing the concentration of PAN increased the fiber diameter from 206 to 506 nm, slightly decreased the surface area and pore size, respectively, from 32.739 to 21.077 m².g-1 and from 6.38 to 4.75 nm. The PAN/TiO2/CNT nanofibers show type IV of the adsorption-desorption N2 isotherms with the H1 hysteresis loops. Membrane PAN/TiO2/CNT at PAN concentration of 6.5% shows the optimum performance on the MB color removal by maintaining the percentage of rejection (%R) at 90% for 240 min and permeability of 750 LMH. [ABSTRACT FROM AUTHOR]