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2D layered semiconductors with excellent light−matter interaction and atomic‐scale thickness have been envisioned as promising candidates for more than Moore and beyond Moore technologies. Here, for the first time, a multi‐functional platform is reported that is fabricated entirely from wrinkle‐free 2D ferroelectric semiconductor α‐In2Se3 integrated with a photodetector, reconfigurable logic switching, and visual perception processing functions. The intensity‐ and wavelength‐dependent resistance is used to demodulate broadband optical information into electrical signals and perform reconfigurable logic switching. Moreover, the platform offers dynamically modulated photosensitive visual sensing in different working modes at the pixel level. Using photo‐assisted piezoresponse force microscopy, the optical‐engineered ferroelectric polarization switch behavior is explored. The platform has excellent sensitivity to both optical and electrical stimuli and can respond to lights in the visible to short‐wavelength infrared region in volatile/non‐volatile manner under gate voltage modulation, with a response of 98 mA W−1 (to 1800 nm light), a current on/off ratio of over 106, and a high field‐effect mobility of 137.55 cm2 V−1 s−1. With its simple structure, unique photoelectric interaction, and controllable operating mechanism, the platform has the potential to simplify the complexity of neuromorphic computing circuitry systems, paving the way for high‐performance hybrid technologies suitable for artificial intelligence applications. [ABSTRACT FROM AUTHOR]

Studying two-dimensional (2D) materials using transmission electron microscopy (TEM) is necessary and very important in many aspects. However, some 2D materials are not resistant to acids or alkalis, which are widely used in normal wet transfer techniques to transfer the exfoliated 2D nanosheets onto the TEM grids. On the other hand, dry stamping method can damage the holey carbon film on the TEM grids. In this article, we present a non-destructive, efficient, and widely applicable transfer method for preparing the TEM samples of the exfoliated 2D materials. Our method only uses the heat-release tape, PMMA, and blue Nitto tape. Neither acid nor alkali is involved in our method, therefore, impurities and damage can be avoided to the greatest extent. The method is also very efficient and can be accomplished in less than 30 min after the exfoliation of the 2D materials. This method is particularly useful for preparing the TEM samples of the 2D materials that are not resistant to acids and alkalis. The present method is also applicable to various 2D materials and various substrates. [ABSTRACT FROM AUTHOR]

α-In2Se3 has attracted increasing attention in recent years due to its excellent electrical and optical properties. Especially, attention has been paid to its peculiar ferroelectric and piezoelectric properties which most other two-dimensional (2D) materials do not possess. This paper presents the first measurement of the thickness-dependent band gaps of few-layer α-In2Se3 by electron energy loss spectroscopy (EELS). The band gap increases with decreasing film thickness which varies from 1.44 eV in a 48 nm thick area to 1.64 eV in an 8 nm thick area of the samples. Further, by combining the improved exchange-correlation potential and proper screening of the internal electric field in an advanced 2D electronic structure technique, we have been able to obtain the structural dependence of the band gap within density functional theory up to hundreds of atoms. This is also the first calculation of a similar type for 2D ferroelectric materials. Both experiment and theory suggest that the variation of the band gap of α-In2Se3 fits well with the quantum confinement model for 2D materials. [ABSTRACT FROM AUTHOR]

Antibiotic resistance has emerged as an imminent threat to public health. It is also increasingly recognized to be a heterogeneous phenomenon: a population of bacteria, found in vivo or in vitro , often consists of a mixture of cells that have different degrees of resistance to antibiotics. The conventional metric to measure antibiotic resistance based on an ensemble-average minimum inhibitory concentration (MIC) fails to characterize the heterogeneity present within a bacterial population. This work describes a droplet microfluidics method to encapsulate single cells from a population consisting of a mixture of antibiotic-sensitive and antibiotic-resistant bacteria. Co-encapsulating viability probe alamarBlue with the cells allows the use of fluorescent drops as a read-out for drops that contain live cells after their exposure to antibiotics. Enumerating the fluorescent drops thus gives the number of resistant cells in the population. Our method enables the quantitative phenotyping of heterogeneous resistance, or heteroresistance, with single-cell resolution. We show that it is possible to detect a resistant sub-population that comprises as low as 10 −6 of the entire population of cells. Such high resolution further allows us to measure the evolution of heteroresistance arising from the exposure of a homogeneous isogenic culture of susceptible cells to sub-lethal dosages of antibiotics. We demonstrate an application of this system to characterize genetic determinants of antimicrobial resistance emergence. The high resolution of phenotypic detection and quantification of minority variants demonstrated in this work has the potential to facilitate the elucidation of the mechanisms underlying heteroresistance. Such understanding will in turn inform the best practices for antibiotic use and containment of antimicrobial resistance in a wide range of settings from agriculture and aquaculture to disease management. Clinically, the ability to quantify and track the composition of a bacterial population will benefit the decision-making process in both the diagnosis and the treatment of bacterial infections, and will ultimately improve patient outcome and avert the spread of resistant populations. [ABSTRACT FROM AUTHOR]

Protein molecules were directly embeddedin metal–organicframeworks (MOFs) by a coprecipitation method. The protein moleculesmajorly embedded on the surface region of MOFs display high biologicalactivities. As a demonstration of the power of such materials, theresulting Cyt cembedded in ZIF-8 showed a 10-foldincrease in peroxidase activity compared to free Cyt cin solution and thus gave convenient, fast, and highly sensitivedetection of trace amounts of explosive organic peroxides in solution. [ABSTRACT FROM AUTHOR]

2D layered semiconductors with excellent light−matter interaction and atomic‐scale thickness have been envisioned as promising candidates for more than Moore and beyond Moore technologies. Here, for the first time, a multi‐functional platform is reported that is fabricated entirely from wrinkle‐free 2D ferroelectric semiconductor α‐In2Se3 integrated with a photodetector, reconfigurable logic switching, and visual perception processing functions. The intensity‐ and wavelength‐dependent resistance is used to demodulate broadband optical information into electrical signals and perform reconfigurable logic switching. Moreover, the platform offers dynamically modulated photosensitive visual sensing in different working modes at the pixel level. Using photo‐assisted piezoresponse force microscopy, the optical‐engineered ferroelectric polarization switch behavior is explored. The platform has excellent sensitivity to both optical and electrical stimuli and can respond to lights in the visible to short‐wavelength infrared region in volatile/non‐volatile manner under gate voltage modulation, with a response of 98 mA W−1 (to 1800 nm light), a current on/off ratio of over 106, and a high field‐effect mobility of 137.55 cm2 V−1 s−1. With its simple structure, unique photoelectric interaction, and controllable operating mechanism, the platform has the potential to simplify the complexity of neuromorphic computing circuitry systems, paving the way for high‐performance hybrid technologies suitable for artificial intelligence applications. [ABSTRACT FROM AUTHOR]

The inherent stability and recalcitrance of benzene ring structures render aromatic compounds a major ecological concern and a substantial risk to human health. Hence, developing a facile and efficacious detection technique for aromatic compounds is essential. As our comprehension of aromatic compound characteristics deepens, microbial cell-based biosensors have emerged as increasingly popular tools in the detection of aromatic compounds. This article introduces the operational principles of microbial whole-cell biosensors and elucidates the construction techniques and applications of electroactive biofilm-based microbial whole-cell sensors, transcription factor-based microbial whole-cell sensors, and degradation gene promoter-dependent microbial whole-cell sensors in the detection of aromatic compounds. In addition, we review the methodologies for improving the performance of microbial whole-cell sensors based on surface display, logic gate construction, genetic circuit modification, and quorum sensing signal amplification.

In recent years, thin layered indium selenide (In 2 Se 3 ) has attracted rapidly increasing attention due to its fascinating properties and promising applications. Here, we report the temperature-driven α-β phase transformation and the enhanced electronic property of 2H α -In 2 Se 3 . We find that 2H α-In 2 Se 3 transforms to β-In 2 Se 3 when it is heated to a high temperature, and the transformation temperature increases from 550 to 650 K with the thickness decreasing from 67 to 17 nm. Additionally, annealing the sample below the phase transformation temperature can effectively improve the electronic property of a 2H α-In 2 Se 3 field-effect transistor, including increasing the on-state current, decreasing the off-state current, and improving the subthreshold swing. After annealing, not only the contact resistance decreases significantly but also the mobility at 300 K increases more than 2 times to 45.83 cm 2 V -1 s -1 , which is the highest among the reported values. Our results provide an effective method to improve the electrical property and the stability of the In 2 Se 3 nanodevices.

α-In 2 Se 3 has attracted increasing attention in recent years due to its excellent electrical and optical properties. Especially, attention has been paid to its peculiar ferroelectric and piezoelectric properties which most other two-dimensional (2D) materials do not possess. This paper presents the first measurement of the thickness-dependent band gaps of few-layer α-In 2 Se 3 by electron energy loss spectroscopy (EELS). The band gap increases with decreasing film thickness which varies from 1.44 eV in a 48 nm thick area to 1.64 eV in an 8 nm thick area of the samples. Further, by combining the improved exchange-correlation potential and proper screening of the internal electric field in an advanced 2D electronic structure technique, we have been able to obtain the structural dependence of the band gap within density functional theory up to hundreds of atoms. This is also the first calculation of a similar type for 2D ferroelectric materials. Both experiment and theory suggest that the variation of the band gap of α-In 2 Se 3 fits well with the quantum confinement model for 2D materials.

Special surface plays a crucial role in nature as well as in industry. Here, the surface morphology evolution of ZnO during wet etching is studied by in situ liquid cell transmission electron microscopy and ex situ wet chemical etching. Many hillocks are observed on the (000 1 ¯ ) O-terminated surface of ZnO nano/micro belts during in situ etching. Nanoparticles on the apex of the hillocks are observed to be essential for the formation of the hillocks, providing direct experimental evidence of the micromasking mechanism. The surfaces of the hillocks are identified to be {01 1 ¯ 3 ¯ } crystal facets, which is different from the known fact that {01 1 ¯ 1 ¯ } crystal facets appear on the (000 1 ¯ ) O-terminated surface of ZnO after wet chemical etching. O 2 plasma treatment is found to be the key factor for the appearance of {01 1 ¯ 3 ¯ } instead of {01 1 ¯ 1 ¯ } crystal facets after etching for both ZnO nano/micro belts and bulk materials. The synergistic effect of acidic etching and O-rich surface caused by O 2 plasma treatment is proposed to be the cause of the appearance of {01 1 ¯ 3 ¯ } crystal facets. This method can be extended to control the surface morphology of other materials during wet chemical etching., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This book chapter describes the use of droplet microfluidics to phenotype single cells. The basic process flow includes the encapsulation of single cells with a specific probe into aqueous micro-droplets suspended in a biocompatible oil. The probe is chosen to measure the phenotype of interest. After incubation, the encapsulated cell turns the probe fluorescent and renders the entire droplet fluorescent. Enumerating drops that are fluorescent quantifies the concentration of cells possessing the phenotype of interest. Examining the distribution of fluorescence further allows one to quantify the heterogeneity among the cell population., (© 2018 Elsevier Inc. All rights reserved.)

This work describes the use of fast-evaporating micro-droplets to finely disperse nanoparticles (NPs) in a polymer matrix for the fabrication of nanocomposites. Agglomeration of particles is a key obstacle for broad applications of nanocomposites. The classical approach to ensure the dispersibility of NPs is to modify the surface chemistry of NPs with ligands. The surface properties of NPs are inevitably altered, however. To overcome the trade-off between dispersibility and surface-functionality of NPs, we develop a new approach by dispersing NPs in a volatile solvent, followed by mixing with uncured polymer precursors to form micro-droplet emulsions. Most of these micro-droplets contain no more than one NP per drop, and they evaporate rapidly to prevent the agglomeration of NPs during the polymer curing process. As a proof of concept, we demonstrate the design and fabrication of TiO 2 NP@PDMS nanocomposites for solar fuel generation reactions with high photocatalytic efficiency and recyclability arising from the fine dispersion of TiO 2 . Our simple method eliminates the need for surface functionalization of NPs. Our approach is applicable to prepare nanocomposites comprising a wide range of polymers embedded with NPs of different composition, sizes, and shapes. It has the potential for creating nanocomposites with novel functions.

This paper describes a method for the quantitative detection of cells expressing BlaC, a β-lactamase naturally expressed by Mycobacterium tuberculosis, intended for the diagnosis of tuberculosis. The method is based on the compartmentalization of bacteria in picoliter droplets at limiting dilutions such that each drop contains one or no cells. The co-encapsulation of a fluorogenic substrate probe for BlaC allows the quantification of bacteria by enumerating the number of fluorescent drops. Quantification of 10 colony forming units per milliliter is demonstrated. Furthermore, the encapsulation of single cell in drops maintains the specificity of the detection scheme even when the concentration of bacteria that do not express BlaC exceeds that expressing BlaC by one million-fold.

This work describes the use of fluorinated Pickering emulsions with nonadsorbing interfaces in droplet-based enzymatic assays. State-of-the-art droplet assays have relied on one type of surfactants consisting of perfluorinated polyether and polyethylene glycol (PFPE-PEG). These surfactants are known to have limitations including the tedious synthesis and interdrop molecular transport which leads to the cross-contamination of droplet contents. Previously we have shown that replacing surfactants with nanoparticles as droplet stabilizers mitigate interdrop transport of small molecules. The nonspecific adsorption of enzymes on nanoparticle surface, however, could cause structural changes in enzymes and consequently the loss of enzymatic activity. To overcome such challenge, we render nanoparticle surface nonadsorbing to enzymes by in situ adsorption of polyethylene glycol (PEG) on particle surfaces. We show that enzyme activities are preserved in droplets stabilized by PEG-adsorbed nanoparticles, and are comparable with those in drops stabilized by PFPE-PEG surfactants. In addition, our nonadsorbing Pickering emulsions successfully prevent interdrop molecular transport, thereby maintaining the accuracy of droplet assays. The particles are also simple and economical to synthesize. The PEG-adsorbed nanoparticles described in this work are thus a competitive alternative to the current surfactant system, and can potentially enable new droplet-based biochemical assays.

A method using ink-jet printing for constructing multi-enzyme systems was proposed, in which a precisely defined enzyme ratio and two-dimensional distribution was obtained by the preset 'color' values. The applications of the print-on-paper multi-enzyme systems were exemplified by the detection of glucose and the design of an enzyme-enabled two-dimensional code.