Customizing Wettability of Defect-Rich CeO2/TiO2 Nanotube Arrays for Humidity-Resistant, Ultrafast, and Sensitive Ammonia Response.

In all their applications, gas sensors should satisfy several requirements, including low cost, reduced energy consumption, fast response/recovery, high sensitivity, and reliability in a broad humidity range. Unfortunately, the fast response/recovery and sensing reliability under high humidity conditions are often still missing, especially those working at room temperature. In this study, a humidity-resistant gas sensor with an ultrafast response/recovery rate was designed by integrating a defect-rich semiconducting sensing interface and a self-assembled monolayer (SAM) with controllable wettability. As a proof-of-concept application, ammonia (NH3), one of the atmospheric and indoor pollutants, was selected as the target gas. The decoration of interconnected defective CeO2 nanowires on spaced TiO2 nanotube arrays (NTAs) provided superior NH3 sensing performances. Moreover, we showed that manipulating the functional end group of SAMs is an efficient and simple method to adjust the wettability, by which 86% sensitivity retention with an ultrafast response (within 5 s) and a low limit of detection (45 ppb) were achieved even at 75% relative humidity and room temperature. This work provides a new route toward the comprehensive design and application of metal oxide semiconductors for trace gas monitoring under harsh conditions, such as those of agricultural, environmental, and industrial fields.

MoO2 Pump-Enhanced Flexible TiO2 Nanojungle-Based Chemiresistors for Rapid Room-Temperature Detection of H2S at Parts-per-Billion Levels.

In this study, we developed a gas sensing platform that can sensitively and specifically detect trace H2S in a high-humidity atmosphere at RT. Upon integrating a carbon nitride (C3N4) nanofilm and molybdenum dioxide (MoO2) nanosheets onto nanojungle-like TiO2 nanotube arrays (TiNTs), the fabricated chemiresistor showed rapid response (38 s)/recovery (58 s) abilities and remarkable detection sensitivity for H2S at concentrations down to 2 ppb, with an estimated detection limit of 1.13 ppb at RT and room-environmental light (REL). Importantly, the gas sensor exhibited satisfactory H2S sensing performance even in dark conditions with a response of 1.9 at 200 ppb. In this design, apart from the architectural advantages of the nanojungle-like TiNTs for accelerating the gas flow efficiency and the abundant sensing sites provided by the C3N4 film, the MoO2 nanosheets act as the essential electron pump not only for the H2S response but also for the subsequent recovery process in air. After employing the MoO2 pump onto C3N4/TiNTs, the response time and recovery time of the system are shortened to ∼35 and ∼11%, respectively. Moreover, we demonstrated the good performance of the flexible gas sensor in detecting trace H2S in human exhaled breath with good humidity resistance. These results highlight the possibility of designing chemiresistors operating in RT and REL conditions and to use these environmentally friendly TiO2-based sensors in real applications.

Rational Integration of SnMOF/SnO2 Hybrid on TiO2 Nanotube Arrays: An Effective Strategy for Accelerating Formaldehyde Sensing Performance at Room Temperature.

Formaldehyde is ubiquitously found in the environment, meaning that real-time monitoring of formaldehyde, particularly indoors, can have a significant impact on human health. However, the performance of commercially available interdigital electrode-based sensors is a compromise between active material loading and steric hindrance. In this work, a spaced TiO2 nanotube array (NTA) was exploited as a scaffold and electron collector in a formaldehyde sensor for the first time. A Sn-based metal-organic framework was successfully decorated on the inside and outside of TiO2 nanotube walls by a facile solvothermal decoration strategy. This was followed by regulated calcination, which successfully integrated the preconcentration effect of a porous Sn-based metal-organic framework (SnMOF) structure and highly active SnO2 nanocrystals into the spaced TiO2 NTA to form a Schottky heterojunction-type gas sensor. This SnMOF/SnO2@TiO2 NTA sensor achieved a high room-temperature formaldehyde response (1.7 at 6 ppm) with a fast response (4.0 s) and recovery (2.5 s) times. This work provides a new platform for preparing alternatives to interdigital electrode-based sensors and offers an effective strategy for achieving target preconcentrations for gas sensing processes. The as-prepared SnMOF/SnO2@TiO2 NTA sensor demonstrated excellent sensitivity, stability, reproducibility, flexibility, and convenience, showing excellent potential as a miniaturized device for medical diagnosis, environmental monitoring, and other intelligent sensing systems.

Single-Nanoparticle-Level Understanding of Oxidase-like Activity of Au Nanoparticles on Polymer Nanobrush-Based Proton Reservoirs.

Enzyme-mimicking nanoparticles play a key role in important catalytic processes, from biosensing to energy conversion. Therefore, understanding and tuning their performance is crucial for making further progress in biological applications. We developed an efficient and sensitive electrochemical method for the real-time monitoring of the glucose oxidase (GOD)-like activity of single nanoparticle through collision events. Using brush-like sulfonate (-SO3-)-doped polyaniline (PANI) decorated on TiO2 nanotube arrays (TiNTs-SPANI) as the electrode, we fabricated a proton reservoir with excellent response and high proton-storage capacity for evaluating the oxidase-like activity of individual Au nanoparticles (AuNPs) via instantaneous collision processes. Using glucose electrocatalysis as a model reaction system, the GOD-like activity of individual AuNPs could be directly monitored via electrochemical tests through the nanoparticle collision-induced proton generation. Furthermore, based on the perturbation of the electrical double layer of SPANI induced by proton injection, we investigated the relationship between the measured GOD-like activities of the plasmonic nanoparticles (NPs) and the localized surface plasmon resonance (LSPR) as well as the environment temperature. This work introduces an efficient platform for understanding and characterizing the catalytic activities of nanozymes at the single-nanoparticle level.

Clinical observation of umbilical cord mesenchymal stem cell transplantation for treating patients receiving peritoneal dialysis.

BACKGROUND: This study aims to observe the outcome and safety of umbilical cord-mesenchymal stem cell (UC-MSC) treatment for continuous ambulatory peritoneal dialysis (CAPD) patients. METHODS: A total of 24 CAPD patients, who underwent UC-MSC treatment from June 2011 to December 2012, were selected for this study. These patients were followed up until June 2015. RESULTS: Results revealed a significant increase in hemoglobin, erythropoietin and albumin levels, a decrease in C-reactive protein levels, and marked improvement in cystatin C and urine volume within three months after UC-MSC transplantation; and the difference was statistically significant (P<0.05). However, the difference in residual glomerular filtration rate, serum creatinine, peritoneal KT/V and remnant kidney KT/V was not statistically significant (P>0.05). CONCLUSIONS: Clinical indicators of patients with CAPD can be partially improved through UC-MSC treatment.