Probing the surface-active sites of metal nanoclusters with atomic precision: a case study of Au5Ag11.

The determination of surface-active sites in metal nanoclusters is of great significance for the in-depth understanding of structural evolutions and physicochemical property mechanisms. In this work, the surface-active sites of the Au5Ag11(DMBT)8(DPPOE)2 cluster template towards metal-/ligand-exchange reactions were unambiguously identified at the atomic level. The active-site tailoring of this nanocluster gave rise to three derivative nanoclusters, Au5Ag9Cu2(DMBT)8(DPPOE)2, Au5Ag11(DMBT)6(DCBT)2(DPPOE)2, and Au5Ag11(DCBT)8(DPPOE)2. The single-crystal structural analysis revealed that all these M16 (M = Au/Ag/Cu) clusters exhibited almost the same framework. Besides, the surface-active site tailoring contributed to significant changes in optical absorptions and emissions of these metal nanoclusters. The findings in this work not only provide an in-depth understanding of the active-site tailoring of cluster surface structures but also develop an intriguing template that enables us to grasp the structure-property correlations at the atomic level.

Effects of two-stage microbial inoculation on organic carbon turnover and fungal community succession during co-composting of cattle manure and rice straw.

This study explored the effects of single-stage inoculation (SSI) versus two-stage inoculation (TSI) on organic carbon components, product quality and fungal community during co-composting of cattle manure and rice straw. Both inoculation methods accelerated the temperature increase and elevated the composting temperature. TSI resulted in a second fermentation stage and extended the thermophilic stage from 22 to 29 days. Compared with SSI, TSI promoted the degradation degree of cellulose, hemicellulose and lignin by 25.9%, 16.5% and 47.4%, and increased the content of total nutrients and humus carbon by 5.9% and 10.5% in final products, respectively. TSI significantly increased the relative abundance of Aspergillus, Trichoderma, Neurospora, Mycothermus, Malbranchea and Gloeophyllum in the second fermentation stage. Spearman correlation analysis indicated that Aspergillus, Neurospora, Trichoderma and Gloeophyllum were the key fungi for lignocellulose degradation and humification. Redundancy analysis showed that temperature was the major environmental factor affecting fungal community succession in TSI.

A three-dimensional cuprous lead bromide framework with highly efficient and stable thermochromic luminescence properties.

Herein, by using a structural design strategy of incorporating hetrometallic halide blocks, we prepared the first 3D bimetallic halide of [H2DABCO]2Cu6PbBr12 with new topological network based on two types of 6-connected nodes. Remarkably, this 3D framework displays highly efficient thermochromic luminescence from broadband yellow to green light emissions with remarkable stability.

Local anomaly detection and quantitative analysis of contaminants in soybean meal using near infrared imaging: The example of non-protein nitrogen.

The melamine scandal indicates that traditional targeted detection methods only detect the specifically listed forms of contamination, which leads to the failure to identify new adulterants in time. In order to deal with continually changing forms of adulterations in food and feed and make up for the inadequacy of targeted detection methods, an untargeted detection method based on local anomaly detection (LAD) using near infrared (NIR) imaging was examined in this study. In the LAD method, with a particular size of window filter and at a 99% level of confidence, a specific value of Global H (GH, modified Mahalanobis distance) can be used as a threshold for anomalous spectra detection and quantitative analysis. The results showed an acceptable performance for the detection of contaminations with the advantage of no need of building a 'clean' library. And, a high coefficient of determination (R2LAD = 0.9984 and R2PLS-DA = 0.9978) for the quantitative analysis of melamine with a limit of detection lower than 0.01% was obtained. This indicates that the new strategy of untargeted detection has the potential to move from passive to active for food and feed safety control.

Impacts of carbonization temperature on the Pb(II) adsorption by wheat straw-derived biochar and related mechanism.

To determine the quantitative correlations between physicochemical characteristics and Pb(II) adsorption amounts of biochar fractions, we prepared wheat straw-derived biochar under various carbonization temperatures (300-900 °C). The different fractions of the wheat straw-derived biochar, water-soluble material (WM), acid-soluble material (AM), and organic material (OM), were acquired. The ash content, ultimate analysis, pH, ion strength (IS), cation exchange capacity (CEC), and acidic functional groups (AFG) were characterized. The Pb(II) adsorption amounts of different biochars and their fractions were determined. The results revealed that the proportions of biochar fractions (WM, AM, and OM) varied with various carbonization temperatures. The maximum Pb(II) adsorption amount of wheat straw-derived biochar (qTotal) was 157.95 ±â€¯0.13 mg/g obtained at 800 °C, and the quantitative correlations between Pb(II) adsorption amount (q) and carbonization temperature (T) can be elaborated by qTotal = 170.72-336.62exp(-0.0035T) (R2 = 0.97), qWM = 106.18-390.10exp(-0.0046T) (R2 = 0.98), qAM = 496.16-477.74exp(-0.0001T) (R2 = 0.79), and qOM = 1.80 + 34.69exp(-0.0038T) (R2 = 0.85). For rate of contribution (RC) for Pb(II) adsorption, when T < 400 °C, the order was AM (60.72 ±â€¯7.33%) > OM (23.41 ±â€¯7.33%) > WM (15.87 ±â€¯0.30%); however, when T ≥ 400 °C, the order was WM (52.31 ±â€¯0.85% - 67.65 ±â€¯2.99%) > AM (29.65 ±â€¯0.46% - 35.77 ±â€¯0.12%) > OM (2.30 ±â€¯0.47% - 12.02 ±â€¯2.43%). Moreover, qWM and qAM exhibited significant positive linear correlations with ash (qWM = 9.92Ash - 123.65, and qAM = 2.13Ash - 0.49), qTotal was predominantly affected by ash content (qTotal = 10.97 Ash - 95.49). The EDX, XRD, and FTIR analysis results further clarified that ion exchange and precipitation were the main adsorption mechanisms for Pb(II) adsorption by wheat straw-derived biochar.

Organic cation directed one-dimensional cuprous halide compounds: syntheses, crystal structures and photoluminescence properties.

In recent years, organic-inorganic hybrid metal halides have emerged as a highly promising class of semiconducting light emitting diodes (LEDs) due to their fascinating photoluminescence properties. Here, by specifically selecting different organic cations as templates, a series of new hybrid cuprous halides have been solvothermally prepared, namely [Me-Py]CuI2 (1), [(Me)2-DABCO]Cu2I4 (2), [Me-MePy]Cu2I3 (3), and [H2DABCO]Cu3X5 (X = I (4) and Br (5)). These hybrid cuprous halides feature one-dimensional (1D) [CuI2]-, [Cu2I3]- and [Cu3X5]2- (X = Br, I) chains surrounded and charge-balanced by organic cations. Under UV photoexcitation, these hybrid cuprous halides exhibit strong tunable photoluminescence from cyan (480 nm) to red (675 nm) emissions with large Stokes shifts (345 nm). The intrinsic nature of PL emissions is also investigated based on temperature-dependent PL emission, lifetime, photoluminescence quantum efficiencies, etc.

Characteristics of tetracycline adsorption by cow manure biochar prepared at different pyrolysis temperatures.

This study aimed to explore the feasibility of using cow manure biochar (CMBC) for adsorption of tetracycline for realizing farm waste treatment and recycling. Three kinds of pyrolysis-temperature CMBCs were prepared and characterized. There were significant differences in the specific surface area, pores structure, surface charge, and oxygen-containing functional groups. The effect of adsorption was not only related to the physicochemical properties of CMBC but also the dosage, solution pH, and ambient temperature. CMBC showed surface heterogeneity, and the adsorption of tetracycline was mainly chemical. Controlling the rate of adsorption was achieved by combining internal particle diffusion and liquid film diffusion. Furthermore, the adsorption was a spontaneous and endothermic process. The use of CMBC as an adsorbent for tetracycline represents a new method for treating and recycling waste in farms. These results could aid in further studies on the adsorption mechanism and optimizing the adsorption process.

Carbonization and ball milling on the enhancement of Pb(II) adsorption by wheat straw: Competitive effects of ion exchange and precipitation.

Straw biomass is a promising adsorbent for the removal of heavy metals. To improve its Pb(II) adsorption capacity and elucidate competition of adsorption mechanisms (e.g., ion exchange and precipitation), the Pb(II) adsorption mechanisms for wheat straw (WS-CK), wheat straw-biochar (WS-BC), and ball-milled wheat straw-biochar (WS-BC + BM) samples were investigated in detail by EDX, XRD, and FTIR. The results implied that the Pb(II) adsorption capacities at an adsorbent dosage of 0.2 g/L onto WS-CK, WS-BC, and WS-BC + BM were 46.33, 119.55, and 134.68 mg/g, respectively. This indicates that carbonization and ball milling are efficient techniques for improving the adsorption capacity of Pb(II) onto wheat straw, as WS-BC and WS-BC + BM exhibited adsorption capacities comparable to other commonly used bioadsorbents. Carbonization contributed significantly to precipitation (e.g., PbCO3 and Pb3(CO3)2(OH)2). Furthermore, competition existed between ion exchange and precipitation during the Pb(II) adsorption process. With relative lower adsorbent dosages, carbonization and ball milling enhanced ion exchange capacity.

Qualitative and quantitative correlation of physicochemical characteristics and lead sorption behaviors of crop residue-derived chars.

This study investigated the key physicochemical characteristics of char that control its ability to absorb Pb2+. Three type of crop residue-derived chars and their ball milled powder were characterized using multiple approaches. The Pb2+ sorption mechanisms of biochar were caused mainly by coprecipitation reactions, which were governed by ionic minerals on chars instead of mineral crystallization (e.g., SiO2 and Al2O3), while coprecipitation reactions and π electronic interaction were the dominant mechanisms of activated carbon. Pearson analysis showed that adsorption quantity (Q) highly correlated with the cation exchange capacity (CEC) (P < 0.01)/oxygen functional groups (OFGs) (P < 0.05) and Q closely correlated with coprecipitation amount (P < 0.01)/complexation amount (P < 0.01). Linear regression equations of sorption amount and CEC (R2 ＞ 0.8)/OFGs (R2 ＞ 0.7) were established. CEC and OFGs of chars are the key factors controlled Pb2+ sorption. These results may promote the development of low-cost, engineered biochar with superior sorption qualities for environmental remediation.

Regularity and mechanism of wheat straw properties change in ball milling process at cellular scale.

To investigate the change of structure and physicochemical properties of wheat straw in ball milling process at cellular scale, a series of wheat straws samples with different milling time were produced using an ultrafine vibration ball mill. A multitechnique approach was used to analyze the variation of wheat straw properties. The results showed that the characteristics of wheat straw powder displayed regular changes as a function of the milling time, i.e., the powder underwent the inversion of breakage to agglomerative regime during wheat straw ball milling process. The crystallinity index, bulk density and water retention capacity of wheat straw were exponential relation with ball milling time. Moreover, ball milling continually converted macromolecules of wheat straw cell wall into water-soluble substances resulting in the water extractives proportional to milling time.

Quantitative approaches for illustrating correlations among the mechanical fragmentation scales, crystallinity and enzymatic hydrolysis glucose yield of rice straw.

Mechanical fragmentation is an important pretreatment in the biomass biotransformation process. Mechanical fragmentation at the tissue scale significantly reduced the particle size of rice straw but did not significantly change its crystalline properties; the increase in the glucose yield was limited from 28.75% (95.55mg/g substrate) to 35.29% (115.28mg/g substrate). Mechanical fragmentation at the cellular scale destroyed the cell wall structure and reduced its crystalline properties. Thus, the glucose yield also showed a significant increase from 35.29% (115.28mg/g substrate) to 81.71% (287.07mg/g of substrate). The quantitative equations among the particle size, crystalline properties and glucose yield (mg/g substrate) are as follows: CrI=44.14×[1-exp(-0.03658×D50)] and CP=(8.403×logD50-24.1836)/(1-4.225/D50^0.5); GY=-5.636CrI+343.7 and GY=-14.62CP+512.1; and GY=97.218+247.5×exp(-0.03824×D50). The quantitative correlations among the mechanical fragmentation scales and crystalline properties can determine the effect and mechanism of mechanical fragmentation on biomass and can further promote the construction of a cost-competitive biotransformation process for biomass.

An electrochemical immunosensor based on interdigitated array microelectrode for the detection of chlorpyrifos.

An electrochemical immunosensor based on interdigitated array microelectrodes (IDAMs) was developed for sensitive, specific and rapid detection of chlorpyrifos. Anti-chlorpyrifos monoclonal antibodies were orientedly immobilized onto the gold microelectrode surface through protein A. Chlorpyrifos were then captured by the immobilized antibody, resulting in an impedance change in the IDAMs surface. Electrochemical impedance spectroscopy was used in conjunction with the fabricated sensor to detect chlorpyrifos. Under optimum conditions, the impedance value change of chlorpyrifos was proportional to its concentrations in the range of 10(0)-10(5) ng/mL. The detection limit was found to be 0.014 ng/mL for chlorpyrifos. The proposed chlorpyrifos immunosensor could be used as a screening method in pesticide determination for the analysis of environmental, agricultural and pharmaceutical samples due to its rapidity, sensitivity and low cost.

Acetylcholinesterase biosensor for carbaryl detection based on interdigitated array microelectrodes.

In this study, an acetylcholinesterase (AChE) biosensor with superior accuracy and sensitivity was successfully developed based on interdigitated array microelectrodes (IAMs). IAMs have a series of parallel microband electrodes with alternating microbands connected together. Chitosan was used as the enzyme immobilization material, and AChE was used as the model enzyme for carbaryl detection to fabricate AChE biosensor. Electrochemical impedance spectroscopy was used in conjunction with the fabricated biosensor to detect pesticide residues. Based on the inhibition of pesticides on the AChE activity, using carbaryl as model compounds, the biosensor exhibited a wide range, low detection limit, and high stability. Moreover, the biosensor can also be used as a new promising tool for pesticide residue analysis.

Amperometric immunosensor for carbofuran detection based on MWCNTs/GS-PEI-Au and AuNPs-antibody conjugate.

In this paper, an amperometric immunosensor for the detection of carbofuran was developed. Firstly, multiwall carbon nanotubes (MWCNTs) and graphene sheets-ethyleneimine polymer-Au (GS-PEI-Au) nanocomposites were modified onto the surface of a glass carbon electrode (GCE) via self-assembly. The nanocomposites can increase the surface area of the GCE to capture a large amount of antibody, as well as produce a synergistic effect in the electrochemical performance. Then the modified electrode was coated with gold nanoparticles-antibody conjugate (AuNPs-Ab) and blocked with BSA. The monoclonal antibody against carbofuran was covalently immobilized on the AuNPs with glutathione as a spacer arm. The morphologies of the GS-PEI-Au nanocomposites and the fabrication process of the immunosensor were characterized by X-ray diffraction (XRD), ultraviolet and visible absorption spectroscopy (UV-vis) and scanning electron microscopy (SEM), respectively. Under optimal conditions, the immunosensor showed a wide linear range, from 0.5 to 500 ng/mL, with a detection limit of 0.03 ng/mL (S/N = 3). The as-constructed immunosensor exhibited notable performance features such as high specificity, good reproducibility, acceptable stability and regeneration performance. The results are mainly due to the excellent properties of MWCNTs, GS-PEI-Au nanocomposites and the covalent immobilization of Ab with free hapten binding sites for further immunoreaction. It provides a new avenue for amperometric immunosensor fabrication.

An amperometric immunosensor based on multi-walled carbon nanotubes-thionine-chitosan nanocomposite film for chlorpyrifos detection.

In this work, a novel amperometric immunosensor based on multi-walled carbon nanotubes-thionine-chitosan (MWCNTs-THI-CHIT) nanocomposite film as electrode modified material was developed for the detection of chlorpyrifos residues. The nanocomposite film was dropped onto a glassy carbon electrode (GCE), and then the anti-chlorpyrifos monoclonal antibody was covalently immobilized onto the surface of MWCNTs-THI-CHIT/GCE using the crosslinking agent glutaraldehyde (GA). The modification procedure was characterized by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimized conditions, a linear relationship between the relative change in peak current of different pulse voltammetry (DPV) and the logarithm of chlorpyrifos solution concentration was obtained in the range from 0.1 to 1.0 × 10(5) ng/mL with a detection limit of 0.046 ng/mL. The proposed chlorpyrifos immunosensor exhibited high reproducibility, stability, and good selectivity and regeneration, making it a potential alternative tool for ultrasensitive detection of chlorpyrifos residues in vegetables and fruits.