A Film Electrode upon Nanoarchitectonics of Bacterial Cellulose and Conductive Fabric for Forehead Electroencephalogram Measurement.

In this paper, we present a soft and moisturizing film electrode based on bacterial cellulose and Ag/AgCl conductive cloth as a potential replacement for gel electrode patches in electroencephalogram (EEG) recording. The electrode materials are entirely flexible, and the bacterial cellulose membrane facilitates convenient adherence to the skin. EEG signals are transmitted from the skin to the bacterial cellulose first and then transferred to the Ag/AgCl conductive cloth connected to the amplifier. The water in the bacterial cellulose moisturizes the skin continuously, reducing the contact impedance to less than 10 kΩ, which is lower than commercial gel electrode patches. The contact impedance and equivalent circuits indicate that the bacterial cellulose electrode effectively reduces skin impedance. Moreover, the bacterial cellulose electrode exhibits lower noise than the gel electrode patch. The bacterial cellulose electrode has demonstrated success in collecting α rhythms. When recording EEG signals, the bacterial cellulose electrode and gel electrode have an average coherence of 0.86, indicating that they have similar performance across different EEG bands. Compared with current mainstream conductive rubber dry electrodes, gel electrodes, and conductive cloth electrodes, the bacterial cellulose electrode has obvious advantages in terms of contact impedance. The bacterial cellulose electrode does not cause skin discomfort after long-term recording, making it more suitable for applications with strict requirements for skin affinity than gel electrode patches.

High-performance perovskite photodetectors based on CsPbBr3 microwire arrays: erratum.

We correct two errors in our publication [Appl. Opt.60, 8896 (2021)APOPAI0003-693510.1364/AO.437478].

Termination dependence and electric field modification of band alignment in a CNT/CH3NH3PbI3 heterojunction.

Carbon nanotube (CNT) and perovskite composite materials possessing the combined advantages of CNTs and perovskites have drawn substantial attention due to their promising applications in photovoltaic and optoelectronic devices. Understanding the band alignment of heterojunctions is crucial for further performance improvement. Here, we systematically investigated the interfacial electronic structure and optical absorption of a semiconducting CNT/CH3NH3PbI3 heterojunction via density functional theory calculations. It was found that the CNT/PbI2-terminated CH3NH3PbI3 (001) surface heterojunction is a type-I band alignment, while the CNT/CH3NH3I-terminated CH3NH3PbI3 (001) surface heterojunction is a type-II band alignment, suggesting the different charge carrier transfer processes as well as termination dependence of band alignment in the CNT/CH3NH3PbI3 heterojunction. Further investigation indicated that applying electric fields can modify the band alignment type in the CNT/CH3NH3PbI3 heterojunction. Our results provide the first insight into the interfacial electronic structure of the CNT/CH3NH3PbI3 heterojunction, which may give a new route for designing optoelectronic devices.

High-performance perovskite photodetectors based on CsPbBr3 microwire arrays.

All inorganic perovskite materials have drawn extensive attention, owing to their outstanding performance, facile solution-processed method, and potential applications in optoelectronic devices. However, uncontrollable morphology, high defect density, and instability of perovskites prepared via solution-processed method are the main challenges for their large-scale production and commercialization. Herein, we prepared large-scale CsPbBr3 microwire arrays with highly ordered morphology and high crystalline quality by a template-assisted method. The photodetectors based on CsPbBr3 microwire arrays exhibited remarkable on/off photocurrent ratio of 9.02×103, high detectivity of 1.59×1013 Jones, high responsivity of 4.55 A/W, and fast response speed of 4.9/3 ms. More importantly, the photocurrent of the photodetectors hardly changed in air after being stored for two months, indicating remarkable stability. This study demonstrates that CsPbBr3 microwire arrays provide the possibility for preparing large-scale and high-performance optoelectronic devices.

Efficient expression of OUC-Sb-lip2 in Yarrowia lipolytica and its comprehensive utilization in the enrichment of DHA and EPA from fish oil.

Lipases are widely used in the modification of functional lipids, particularly in the enrichment of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). In this study, a lipase named OUC-Sb-lip2 was expressed in Yarrowia lipolytica, achieving a promising enzyme activity of 472.6 U/mL by optimizing the culture medium, notably through olive oil supplementation. A significant proportion (58.8%) of the lipase activity was located in the cells, whereas 41.2% was secreted into the supernatant. Both whole-cell and immobilized OUC-Sb-lip2 were used to enrich DHA and EPA from fish oil. The whole-cell approach increased the DHA and EPA contents to 2.59 and 2.55 times that of the original oil, respectively. Similarly, the immobilized OUC-Sb-lip2 resulted in a 2.00-fold increase in DHA and an 1.99-fold increase in EPA after a 6-h hydrolysis period. Whole cell and the immobilized OUC-Sb-lip2 retained 48.7% and 52.7% of their activity after six cycles of reuse, respectively.

Concave gold nano-arrows (AuCNAs) for efficient catalytic reduction of 4-nitrophenol.

Anisotropic gold nanostructures have attracted great attention in different fields including catalysis. Thermodynamically driven selective surface growth offers a reliable and reproducible method for anisotropic gold nanoparticle synthesis with specific morphologies. Herein, monocrystalline concave gold nano-arrows (AuCNAs) are prepared by the over-growth method using Au nanorods (AuNRs) as seeds. The as-prepared AuCNAs consist of a biconical head and four concave structures. Interestingly, silver ions (Ag+) concentration significantly affects the product morphology by tuning the peak positions of surface plasmon resonance (SPR), aspect ratio, arrow, and concave morphology of AuCNAs. The position of longitudinal SPR peaks is observed at 810, 805 and 782 nm at [Ag+]/[Au3+] molar ratios of 1:2, 1:1, and 2:1, respectively. Diameters and lengths of AuCNAs varied from 25 nm to 36 nm; 104 nm, 78 nm, and 120 nm, respectively. Additionally, the AuCNAs are applied for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in presence of excess NaBH4. Compared to gold nanorods (AuNRs), the prepared AuCNAs catalyst shows excellent catalytic activity, demonstrating that concave structures and sharp corners significantly enhance the catalytic activity. The value of pseudo-first-order reaction kinetic constants (kapp) increased from 0.0051 to 0.0195 s-1 with increasing catalyst valume from 7.5 to 37.5 µL. The highest normalized reaction rate constant (Knor) and turnover frequency (TOF) reach 5.84 × 104 min-1 mmol-1 and 443.47 h-1, respectively, at [Ag+]/[Au3+] ratio of 1:1 in AuCNAs catalyst. This study expands catalytic applications of anisotropic gold nanostructures and widens their potential application areas, such as surface plasmon exciton photonics, biomedical photonics, and photocatalysis.

A Methodology for Enhancing SSVEP Features Using Adaptive Filtering Based on the Spatial Distribution of EEG Signals.

In this paper, we propose a classification algorithm of EEG signal based on canonical correlation analysis (CCA) and integrated with adaptive filtering. It can enhance the detection of steady-state visual evoked potentials (SSVEPs) in a brain-computer interface (BCI) speller. An adaptive filter is employed in front of the CCA algorithm to improve the signal-to-noise ratio (SNR) of SSVEP signals by removing background electroencephalographic (EEG) activities. The ensemble method is developed to integrate recursive least squares (RLS) adaptive filter corresponding to multiple stimulation frequencies. The method is tested by the SSVEP signal recorded from six targets by actual experiment and the EEG in a public SSVEP dataset of 40 targets from Tsinghua University. The accuracy rates of the CCA method and the CCA-based integrated RLS filter algorithm (RLS-CCA method) are compared. Experiment results show that the proposed RLS-CCA-based method significantly improves the classification accuracy compared with the pure CCA method. Especially when the number of EEG leads is low (three occipital electrodes and five non occipital electrodes), its advantage is more significant, and accuracy reaches 91.23%, which is more suitable for wearable environments where high-density EEG is not easy to collect.

[Pollution Characteristics and Source Apportionment of Heavy Metals in Vegetable Field in the Three Gorges Reservoir Area (Chongqing Section)].

To explore the pollution characteristics, ecological risks, and sources of heavy metals, soil surface samples of vegetable fields in 14 typical districts of the Three Gorges Reservoir area (Chongqing section) were collected in October 2021. The contents of seven types of heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) were analyzed. Based on the single-factor pollution index, the Nemerow integrated pollution index and potential ecological risk coefficient of heavy metals were evaluated. Additionally, the effects of different planting years and methods (open-field and greenhouse planting) on soil heavy metal accumulation were analyzed. The results indicated that the mean concentrations of heavy metals in vegetable soils in the area were lower than the national risk screening values for soil contamination of agricultural land (GB 15618-2018) but higher than their background values in Chongqing. According to the single-factor pollution index method, Pb, Zn, Cu, and Cd showed negligible slight hazards. The Nemerow pollution index showed that the study area was at a slight hazard level, and the main factors were Ni and Cd. Heavy metal pollution was found in 91.4% of the soil samples (PN>1) with different degrees, and 9.19% of them were severely polluted. The potential ecological risk coefficient showed that the vegetable lands were polluted slightly, and 9.77% of soil samples polluted by Cd were at moderate ecological risk. According to cluster analysis, the sources of Cd-Cu-Pb-Zn and As-Cr-Ni were similar. The content of heavy metals in the open field and greenhouse showed an increasing trend with the increase in planting years, and the content of heavy metals in greenhouse soil were generally higher than that in open field soil.

[Pollution Characteristics and Ecological Risk Assessment of Antibiotics in Vegetable Field in Kaizhou, Chongqing].

The accumulation of antibiotics in farmland and its ecological risk have become a research hotspot at home and abroad. The objective of this study was to investigate the occurrence and accumulation of antibiotics and their potential environmental and ecological risks in vegetable fields in Kaizhou district of Chongqing country. The occurrence characteristics of antibiotics including tetracyclines, sulfonamides, quinolones, macrolides, and chloramphenicols were detected using experimental analysis. The results showed that there was an accumulation of antibiotics in the vegetable soil, and 18 antibiotics in five categories were detected (0-42.88 µg·kg-1), mainly for tetracyclines and quinolones. The detection rate of quinolone antibiotics was the highest (15.38%-100%), especially for norfloxacin and ofloxacin (100%), whereas the tetracyclines presented the highest concentration (0-42.88 µg·kg-1). The amount of total antibiotics in the vegetable soil was 1.64-233.11 µg·kg-1, whereas different vegetable soils showed the following trend:water spinach soil (89.73 µg·kg-1)>cabbage soil (32.53 µg·kg-1)>pepper soil (32.16 µg·kg-1)>tomato soil (32.13 µg·kg-1)>cucumber soil (26.46 µg·kg-1)>grassland (7.32 µg·kg-1). The correlation results showed that there was a significantly positive correlation between total antibiotic residues and organic fertilizer application (P<0.05) but a significantly negative correlation with soil pH (P<0.05). Quinolones and sulfonamides were negatively correlated with soil water content (P<0.05), whereas quinolones positively correlated with soil available phosphorus and organic matter content (P<0.05). The potential eco-environmental risk assessment results showed that tetracyclines and quinolones in vegetable soil in Kaizhou district had certain ecological risks, of which 62%-92% and 62%-100% of soil samples with quinolones had potential toxicity to soil animals and microorganisms.

Biochemical characterization of two ß-N-acetylglucosaminidases from Streptomyces violascens for efficient production of N-acetyl-d-glucosamine.

Chitin, one of the most abundant renewable biopolymers on Earth, is commercially available from crustacean wastes. One critical step in converting chitin to high-value products is its degradation by chitinolytic enzymes to N-acetyl-d-glucosamine (GlcNAc), which plays a significant role in functional food and pharmaceutical industries. Here, we cloned and biochemically characterized two novel ß-N-acetylglucosaminidases named SvNag2557 (family-84) and SvNag4755 (family-3) from Streptomyces violascens ATCC 27968. Both SvNag2557 and SvNag4755 exhibited strict substrate specificity toward N-acetyl chitooligosaccharides with GlcNAc as the sole product. Thus, a one-pot production for pure GlcNAc from chitin by an enzyme cocktail reaction was further developed. Under the co-action of an endo-type chitinase SaChiA4 and SvNag2557 (mass ratio 1:2), the final conversion rates of colloidal chitin and ionic liquid pretreated chitin to GlcNAc were 80.2% and 73.8% with GlcNAc purities of 99.7% and 96.8%, respectively.

Identification of a GDSL lipase from Streptomyces bacillaris and its application in the preparation of free astaxanthin.

Astaxanthin shows multiple biological activities, but it is usually linked to different fatty acids and exists in the form of esters. The complexity of astaxanthin esters limits their application in the preparation of sophisticated drugs. Herein, a novel lipase from Streptomyces bacillaris that could hydrolyze astaxanthin esters, named OUC-Sb-lip12, was expressed in Bacillus subtilis. The active site of OUC-Sb-lip12 is probably composed of a dyad of Ser48 and His254, instead of a typical catalytic triad. The lipase was identified to be a GDSL hydrolase, and it showed highest activity at 45 °C and pH 9.0 (glycine-NaOH buffer). OUC-Sb-lip12 showed a good stability at its optimum temperature or a higher temperature, retaining 88.4% and 80.6% of its activity after incubating for 36 h at 45 °C and 55 °C, respectively. OUC-Sb-lip12 could effectively hydrolyze astaxanthin esters in Haematococcus pluvialis oil, generating free astaxanthin. Under the optimum conditions, 96.29% astaxanthin esters were hydrolyzed in 12 h. In addition, B.subtilis is a GRAS model strain and it could efficiently secrete lipase in 9 h, making the lipase potential for scale production of free astaxanthin, which could be further used in the preparation of specific astaxanthin esters with specific functions.

A novel flexible hydrogel electrode with a strong moisturizing ability for long-term EEG recording.

Objective. A novel flexible hydrogel electrode with a strong moisturizing ability was prepared for long-term electroencephalography (EEG) monitoring.Approach. The hydrogel was synthesized by polymerizing the N-acryloyl glycinamide monomer. And a proper amount of glycerin was added to the hydrogel to increase the moisture retention ability of the electrodes. The hydrogel shows high mechanical properties, and the liquid in the hydrogel produces a hydrating effect on the skin stratum corneum, which could decrease the contact impedance between skin and electrode. In addition, the installation of hydrogel electrode is very convenient, and the skin of the subject does not need to be abraded.Main results. Scanning electron microscope images show that there are a large number of micropores in the hydrogel, which provide storage space for water molecules. The average potential drift of the hydrogel electrode is relatively low (1.974 ± 0.560µV min-1). The average contact impedance of hydrogel electrode in forehead region and hair region are 6.43 ± 0.84 kΩ cm2and 13.15 ± 3.72 kΩ cm2, respectively. The result of open/closed paradigm, steady-state visual evoked potentials, and P300 visual evoked potential show that hydrogel electrode has excellent performance. Compared with the hydrogel without glycerin, the moisture retention ability of hydrogel containing glycerin was greatly improved.Significance.Compared with standard Ag/AgCl wet electrode, hydrogel electrode is more convenient to install and has strong moisture retention ability, which makes it have great potential in daily life for long-term EEG recording.

Identification of an alkaline lipase capable of better enrichment of EPA than DHA due to fatty acids selectivity and regioselectivity.

The whole genome of Streptomyces violascens (=ATCC 27968) was sequenced and the cloning and expression of OUC-Lipase 6 were conducted in Bacillus subtilis WB800. The recombinant enzyme belongs to the lipolytic enzymes family V. OUC-Lipase 6 showed optimal activity at 30 °C and pH 9.0, and retained 90.2% of its activity in an alkaline buffer (pH 8.0, 30 °C and 96 h). OUC-Lipase 6 showed good stability under medium temperature conditions (residual activity of 68.8%, pH 8.0, 45 °C and 96 h). OUC-Lipase 6 could selectively hydrolyze fatty acids on the glyceride backbone, thus improving the contents of DHA and EPA in codfish oil. OUC-Lipase 6 also showed regioselectivity, resulting in a better enrichment efficiency for EPA than DHA. After hydrolyzing for 36 h via OUC-Lipase 6, the contents of EPA and DHA were improved to 3.24-fold and 1.98-fold, respectively.

A Novel Bristle-Shaped Semi-Dry Electrode With Low Contact Impedance and Ease of Use Features for EEG Signal Measurements.

OBJECTIVE: In this paper, we present a novel soft bristle-shaped semi-dry electrode for electroencephalography (EEG) recording. Because the bristle-shaped structure with electric conductivity could overcome the obstacle of hair and enable direct connection to scalp, the semi-dry electrode could work with drinking water instead of saline water that was widely used in previous semi-dry or water electrodes to improve its convenience. The electrode consisted of conductive bristles and a 3D-printed casing. Carbon-coated nylon conductive bristles could achieve low impedance and soft properties of the semi-dry electrode. The bristles could spread on skin and realize a larger contact area. The carbon-coated conductive bristles could also continuously penetrate water into the corneum of skin to reduce contact impedance. The contact impedance of the bristle-shaped semi-dry electrode was similar to the traditional wet electrode, but much lower than dry electrode. Although the saline water had much lower impedance than drinking water, our electrode still achieved even lower skin-electrode contact impedance than previous semi-dry or water electrode with saline water. The alpha rhythms, P300 visual evoked potential, and steady-state visual evoked potential were, respectively, measured to evaluate the electrode performance for EEG recording.

Hydroxide assisted synthesis of monodisperse and biocompatible gold nanoparticles with dextran.

A simple and rapid approach to synthesize monodisperse and biocompatible gold nanoparticles (AuNPs) employing dextran as a reducing and stabilizing agents at different reaction conditions was described. The obtained dextran-gold nanoparticles (Dex-AuNPs) were characterized by transmission electron microscopy (TEM), UV-Vis spectroscopy, Nuclear magnetic resonance (NMR) spectroscopy, Fourier transformer infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis. The TEM examinations showed the resultant particles were 4-50 nm in size, monodispersity and uniform particle size distribution. Moreover, the size of the nanoparticles can be controlled by varying the concentration of the reactants. UV-Vis spectra showed that the characteristic localized surface plasmon resonance (LSPR) band of AuNPs was at about 525 nm. NMR spectroscopy and FTIR spectroscopic analysis suggested the detailed structural information of dextran before and after synthesis of AuNPs. XRD and selected area electron diffraction (SAED) pattern analysis demonstrated that the colloidal nanoparticles had a well crystallized structure. The experimental analyses revealed that NaOH played an important role in the synthesis of Dex-AuNPs. And the possible formation mechanism of the fabrication of these Dex-AuNPs was also proposed. MTT assay was utilized to evaluate the cytotoxicity of the synthesized Dex-AuNPs on HeLa cells and SiHa cells. These results suggested that the prepared Dex-AuNPs complexes had excellent biocompatibility and acted as a candidate for further biomedical application.

Calculation extinction cross sections and molar attenuation coefficient of small gold nanoparticles and experimental observation of their UV-vis spectral properties.

Gold nanoparticles (AuNPs) have been researched extensively, such as applied in various biosensors, biomedical imaging and diagnosis, catalysis and physico-chemical analysis. These applications usually required to know the nanoparticle size or concentration. Researchers have been studying a simply and quick way to estimate the concentration or size of nanoparticles from their optical spectra and SPR feature for several years. The extinction cross-sections and the molar attenuation coefficient were one of the key parameters. In this study, we calculated the extinction cross-sections and molar attenuation coefficient (decadic molar extinction coefficient) of small gold nanoparticles by dipole approximation method and modified Beer-Lambert law. The theoretical result showed that the surface plasmon resonance peak of small gold nanoparticles was blueshift with an increase size. Moreover, small AuNPs (sub-10nm) were prepared by using of dextran or trisodium citrate as reducing agent and capping agent. The experimental synthesized AuNPs was also shows a blueshift as increasing particle size in a certain range. And the concentration of AuNPs was calculated based on the obtained molar attenuation coefficient. For small nanoparticles, the size of nanoparticles and surface plasmon resonance property was not showed a positive correlation compared to larger nanoparticles. These results suggested that SPR peak depended not only on the nanoparticle size and shape but also on the nanoparticles environment.

Fabrication of Carbon Nanowire Arrays Using Inhomogeneous Dissolution-Diffusion Kinetics and Photoresist Pyrolysis.

We report a simple and efficient method to fabricate carbon nanowire (CNW) arrays with precise locations and spatial arrangements. This method is based on a phenomenon in photoresist (PR) development that if the exposed posts are close-spaced they are linked by some undissolved resist filaments. Pyrolysis made the residual resist filaments to shrink and form CNWs under an inert atmosphere. Scanning electron microscope (SEM) showed that these nanowires had orderly arrangement and precise location. The formation of the CNWs was studied by simulation and experiment, which indicated the nanowire was influenced by the thickness of PR, the spacing distance between exposed posts, the diameter of posts and the developing time. We also investigated the composition and electrical properties of the resultant CNWs. The results showed that the CNW had characteristics of p type semiconductor.

An equipment-free polydimethylsiloxane microfluidic spotter for fabrication of microarrays.

This paper presents a low-cost, power-free, and easy-to-use spotter system for fabrication of microarrays. The spotter system uses embedded dispensing microchannels combined with a polydimethylsiloxane (PDMS) membrane containing regular arrays of well-defined thru-holes to produce precise, uniform DNA or protein microarrays for disease diagnosis or drug screening. Powered by pre-evacuation of its PDMS substrate, the spotter system does not require any additional components or external equipment for its operation, which can potentially allow low-cost, high-quality microarray fabrication by minimally trained individuals. Polyvinylpyrrolidone was used to modify the PDMS surface to prevent protein adsorption by the microchannels. Experimental results indicate that the PDMS spotter shows excellent printing performance for immobilizing proteins. The measured coefficient of variation (CV) of the diameter of 48 spots was 2.63% and that of the intensity within one array was 2.87%. Concentration gradient experiments revealed the superiority of the immobilization density of the PDMS spotter over the conventional pin-printing method. Overall, this low-cost, power-free, and easy-to-use spotting system provides an attractive new method to fabricate microarrays.