An accurate, rapid, and cost‐effective biosensor for the quantification of disease biomarkers is vital for the development of early‐diagnostic point‐of‐care systems. The recent discovery of the trans‐cleavage property of CRISPR type V effectors makes CRISPR a potential high‐accuracy bio‐recognition tool. Herein, a CRISPR‐Cas12a (cpf1) based electrochemical biosensor (E‐CRISPR) is reported, which is more cost‐effective and portable than optical‐transduction‐based biosensors. Through optimizing the in vitro trans‐cleavage activity of Cas12a, E‐CRIPSR was used to detect viral nucleic acids, including human papillomavirus 16 (HPV‐16) and parvovirus B19 (PB‐19), with a picomolar sensitivity. An aptamer‐based E‐CRISPR cascade was further designed for the detection of transforming growth factor β1 (TGF‐β1) protein in clinical samples. As demonstrated, E‐CRISPR could enable the development of portable, accurate, and cost‐effective point‐of‐care diagnostic systems.

Manganese dioxides (MnO) are among important environmental oxidants in contaminant removal; however, most existing work has only focused on naturally abundant MnO. We herein report the effects of different phase structures of synthetic MnO on their oxidative activity with regard to contaminant degradation. Bisphenol A (BPA), a frequently detected contaminant in the environment, was used as a probe compound. A total of eight MnO with five different phase structures (α-, β-, γ-, δ-, and λ-MnO) were successfully synthesized with different methods. The oxidative reactivity of MnO, as quantified by pseudo-first-order rate constants of BPA oxidation, followed the order of δ-MnO-1 > δ-MnO-2 > α-MnO-1 > α-MnO-2 ≈ γ-MnO > λ-MnO > β-MnO-2 > β-MnO-1. Extensive characterization was then conducted for MnO crystal structure, morphology, surface area, reduction potential, conductivity, and surface Mn oxidation states and oxygen species. The results showed that the MnO oxidative reactivity correlated highly positively with surface Mn(III) content and negatively with surface Mn average oxidation state but correlated poorly with all other properties. This indicates that surface Mn(III) played an important role in MnO oxidative reactivity. For the same MnO phase structure synthesized by different methods, higher surface area, reduction potential, conductivity, or surface adsorbed oxygen led to higher reactivity, suggesting that these properties play a secondary role in the reactivity. These findings provide general guidance for designing active MnO for cost-effective water and wastewater treatment.

An accurate, rapid, and cost‐effective biosensor for the quantification of disease biomarkers is vital for the development of early‐diagnostic point‐of‐care systems. The recent discovery of the trans‐cleavage property of CRISPR type V effectors makes CRISPR a potential high‐accuracy bio‐recognition tool. Herein, a CRISPR‐Cas12a (cpf1) based electrochemical biosensor (E‐CRISPR) is reported, which is more cost‐effective and portable than optical‐transduction‐based biosensors. Through optimizing the in vitro trans‐cleavage activity of Cas12a, E‐CRIPSR was used to detect viral nucleic acids, including human papillomavirus 16 (HPV‐16) and parvovirus B19 (PB‐19), with a picomolar sensitivity. An aptamer‐based E‐CRISPR cascade was further designed for the detection of transforming growth factor β1 (TGF‐β1) protein in clinical samples. As demonstrated, E‐CRISPR could enable the development of portable, accurate, and cost‐effective point‐of‐care diagnostic systems.

Solid state gas sensors are a core enabling technology to a range of measurement applications including industrial, safety, and environmental monitoring. The technology associated with solid-state gas sensors has evolved in recent years with advances in materials, and improvements in processing and miniaturization. In this review, we examine the state-of-the-art of solid state gas sensors with the goal of understanding the core technology and approaches, various sensor design methods to provide targeted functionality, and future prospects in the field. The structure, detection mechanism, and sensing properties of several types of solid state gas sensors will be discussed. In particular, electrochemical cells (solid and liquid), impedance/resistance based sensors (metal oxide, polymer, and carbon based structures), and mechanical sensing structures (resonators, cantilevers, and acoustic wave devices) as well as sensor arrays and supporting technologies, are described. Development areas for this field includes increased control of material properties for improved sensor response and durability, increased integration and miniaturization, and new material systems, including nano-materials and nano-structures, to address shortcomings of existing solid state gas sensors.

AC impedance spectroscopy has been performed on 40 mol% gadolinia-doped ceria electrodes on yttria stabilized zirconia (YSZ) at 700-950°C in reducing CO/CO 2 atmospheres. Area-specific-resistance (ASR) values for this electrode were in the range of 0.8-37 Ω-cm 2 , about two orders of magnitude lower than measurements on Pt electrodes and slightly lower than data on Ni-YSZ electrodes in the literature under similar temperature and partial pressure of oxygen (P O 2 ) conditions. A continuum-based model of this electrode is described and an analysis performed to extract the vacancy diffusion coefficient (D v ) and surface exchange rate coefficient (R 0 ) as a function of temperature and P O 2 , from the impedance results. The D v data agree reasonably well with published measurements of the tracer diffusion coefficient (D ⁎ ) based on isotope profiling by secondary ion mass spectroscopy (SIMS) and conductivity measurements on 40 mol% GDC. The R 0 values are a factor of 3 lower than the published measurements of the surface reaction rate (k) obtained from isothermal thermogravimetric relaxation, and decrease with increasing P O 2 . Values of the thermodynamic factor (A) calculated from the fitted model parameters matched well with those calculated from oxygen nonstoichiometry data in the literature. Published by Elsevier B.V.