Quantitative analysis of galactose using LDI-TOF MS based on a TiO2 nanowire chip

A novel method for quantifying galactose was developed to serve as a newborn screening test for galactosemia using laser desorption/ionization time-of-flight (LDI-TOF) mass spectrometry (MS) with a TiO2 nanowire chip. Herein, phosphate citrate buffer, serum, and dried blood spot (DBS) were employed for the quantitative analysis of galactose. To quantitatively analyze galactose, its reduction potential was used to oxidize o-phenylene diamine (OPD) into 2,3-diaminophenazine (DA), which were both detected using LDI-TOF MS with a TiO2 nanowire chip according to the concentration of galactose. The reproducibility and the interference of glucose were determined to demonstrate the applicability of this method. Moreover, mixtures of galactose, phenylalanine, and 17 α-OHP were analyzed to determine the interference induced by other biomarkers of metabolic disorders. The OPD oxidation of galactose was found to be selectively achieved under high-glucose conditions, similar to human blood, thereby showing good reproducibility. The intensities of the mass peaks of OPD and DA based on LDI-TOF MS with a TiO2 nanowire chip were linearly correlated in the galactose concentration range of 57.2–220.0 μg/mL (r2 = 0.999 and 0.950, respectively) for serum samples and 52.5–220.0 μg/mL (r2 = 0.993 and 0.985, respectively) for DBS after methanol precipitation/extraction. The enzyme immunoassay and LDI-TOF MS analysis results were statistically analyzed, and a mixture of phenylalanine, 17 α-OHP, and galactose was simultaneously investigated quantitatively at the cutoff level.

Catalyst Recovery, Regeneration and Reuse during Large-Scale Disinfection of Water Using Photocatalysis

The deployment of photocatalysis for remediation of water has not yet been realized, although laboratory-scale studies have demonstrated promise. Accomplishing this requires the development of photocatalysis as a process, including studying its efficiencies in remedying water when high volumes of water are processed, and addressing the recovery, possible regeneration and reuse of the photocatalysts. To that end, this work is aimed at demonstrating the use of a custom-built mobile platform for disinfecting large quantities of water. The benchtop platform built is capable of processing 15.14 L (4 gallons) per minute of water, with possibility for further scale-up. Preliminary studies on the catalyst recovery, regeneration and reuse via gravity-assisted settling, centrifugation and air plasma treatment indicated that 77% of Aeroxide® P25 titania (TiO2) nanoparticle and 57% of porous TiO2 nanowire photocatalysts could be recovered and regenerated for further use. Overall, this study indicated that process improvements, including increasing the kinetics of the photocatalysis, and optimization of the efficacies of the catalyst recovery and regeneration processes will make it useful for water remediation on any scale. More importantly, the portable and flexible nature of the benchtop photocatalysis system makes it amenable for use in conjunction with existing technologies for remedying large quantities of water.

Sieve-Like CNT Film Coupled with TiO2 Nanowire for High-Performance Continuous-Flow Photodegradation of Rhodamine B under Visible Light Irradiation

Continuous-flow photoreactors hold great promise for the highly efficient photodegradation of pollutants due to their continuity and sustainability. However, how to enable a continuous-flow photoreactor with the combined features of high photodegradation efficiency and durability as well as broad-wavelength light absorption and large-scale processing remains a significant challenge. Herein, we demonstrate a facile and effective strategy to construct a sieve-like carbon nanotube (CNT)/TiO2 nanowire film (SCTF) with superior flexibility (180° bending), high tensile strength (75–82 MPa), good surface wettability, essential light penetration and convenient visible light absorption. Significantly, the unique architecture, featuring abundant, well-ordered and uniform mesopores with ca. 70 µm in diameter, as well as a homogenous distribution of TiO2 nanowires with an average diameter of ca. 500 nm, could act as a “waterway” for efficient solution infiltration through the SCTF, thereby, enabling the photocatalytic degradation of polluted water in a continuous-flow mode. The optimized SCTF-2.5 displayed favorable photocatalytic behavior with 96% degradation of rhodamine B (RhB) within 80 min and a rate constant of 0.0394 min−1. The continuous-flow photodegradation device made using SCTF-2.5 featured exceptional photocatalytic behavior for the continuous degradation of RhB under simulated solar irradiation with a high degradation ratio (99.6%) and long-term stability (99.2% retention after working continuously for 72 h). This work sheds light on new strategies for designing and fabricating high-performance continuous-flow photoreactors toward future uses.

TiO2 Nanowire Arrays in situ Grown on Ti Foil Exhibiting Superior Uranyl-Adsorption Properties

TiO2 nanowire arrays in situ grown on Ti foil (TiO2/Ti) were prepared to remove uranium (VI) from aqueous solution. As the Ti foil serves as a carrier for TiO2, the TiO2/Ti adsorbent can be effortlessly retrieved from aqueous solutions by tweezers after adsorption. The presence of TiO2 nanowire arrays on Ti foil was verified by X-ray diffraction and scanning electron microscopy. Parameters in the adsorption process were fully evaluated, including solution pH, contact time, temperature, and uranium (VI) concentration. The adsorption was most efficient in the pH range of 5.0 to 9.0. The maximum uranium (VI) adsorption capacity of TiO2/Ti, based on the Langmuir model, was 354.5 mg g–1 at pH 5.0 and T = 323 K. Thermodynamic parameters showed that the adsorption of uranium (VI) on TiO2/Ti is endothermic and spontaneous. The adsorption capacity of TiO2/Ti remained essentially unchanged after three adsorption–desorption cycles in uranium (VI) solutions. Our results support the application of this adsorbent to removal of uranium (VI) from diversified aqueous samples.