A novel fluorescent aptasensor for sensitive and selective detection of environmental toxins fumonisin B1 based on enzyme-assisted dual recycling amplification and 2D δ-FeOOH-NH2 nanosheets.

Fumonisin (FB) is a pervasive hazardous substance in the environment, presenting significant threats to human health and ecological systems. Thus, the selective and sensitive detection of fumonisin B1 (FB1) is crucial due to its high toxicity and wide distribution in corn, oats, and related products. In this work, we developed a novel and versatile fluorescent aptasensor by combining enzyme-assisted dual recycling amplification with 2D δ-FeOOH-NH2 nanosheets for the determination of FB1. The established CRISPR/Cas12a system was activated by using activator DNA (aDNA), which was released via a T7 exonuclease-assisted recycling reaction. Additionally, the activated Cas12a protein was utilized for non-specifically cleavage of the FAM-labeled single-stranded DNA (ssDNA-FAM) anchored on δ-FeOOH-NH2 nanosheets. The pre-quenched fluorescence signal was restored due to the desorption of the cleaved ssDNA-FAM. Due to the utilization of this T7 exonuclease-Cas12a-δ-FeOOH-NH2 aptasensor for signal amplification, the detection range of FB1 was expanded from 1 pg/mL to 100 ng/mL, with a limit of detection (LOD) as low as 0.45 pg/mL. This study not only provides novel insights into the development of fluorescence biosensors based on 2D nanomaterials combined with CRISPR/Cas12a, but also exhibits remarkable applicability in detecting other significant targets.

The Morphology Dependent Interaction between Silver Nanoparticles and Bovine Serum Albumin.

Biological applications of silver nanoparticles (AgNPs) depend on the covalently attached or adsorbed proteins. A series of biological effects of AgNPs within cells are determined by the size, shape, aspect ratio, surface charge, and modifiers. Herein, the morphology dependent interaction between AgNPs and protein was investigated. AgNPs with three different morphologies, such as silver nanospheres, silver nanorods, and silver nanotriangles, were employed to investigate the morphological effect on the interaction with a model protein: bovine serum albumin (BSA). The adsorptive interactions between BSA and the AgNPs were probed by UV-Vis spectroscopy, fluorescence spectroscopy, dynamic light scattering (DLS), Fourier transform infrared spectrometry (FTIR), transmission electron microscopy (TEM), and circular dichroism (CD) techniques. The results revealed that the particle size, shape, and dispersion of the three types of AgNPs markedly influence the interaction with BSA. Silver nanospheres and nanorods were capsulated by protein coronas, which led to slightly enlarged outer size. The silver nanotriangles evolved gradually into nanodisks in the presence of BSA. Fluorescence spectroscopy confirmed the static quenching the fluorescence emission of BSA by the three AgNPs. The FTIR and CD results suggested that the AgNPs with different morphologies had different effects on the secondary structure of BSA. The silver nanospheres and silver nanorods induced more pronounced structural changes than silver nanotriangles. These results suggest that the formation of a protein corona and the aggregation behaviors of AgNPs are markedly determined by their inherent morphologies.

Fluorescence off-on nanosensor based on MoS2 nanosheets and oligonucleotides for the alternative detection of mercury(II) ions or silver(I) ions.

As traditional methods for detection of heavy metal pollution in water involve complex procedures and require expensive equipment, there is a great deal of interest in the development of rapid and simple methods for determining heavy metal ions in water. Here, a nanobiosensor based on molybdenum disulphide (MoS2) nanosheets and fluorophore (FAM) labeled oligonucleotides was proposed, and fluorescence spectroscopy was adopted for detection of Hg2+ or Ag+ ions in aqueous solution. The principle underlying detection by the sensor involves the formation of T-Hg2+-T or C-Ag+-C mismatches by single-stranded DNA (ssDNA) rich in thymine (T) or cytosine (C), thereby forming stable double-stranded DNA (dsDNA) structures. By exploiting the different adsorption capacity of MoS2 nanosheets for ssDNA and dsDNA, when oligonucleotides were in a single chain state, MoS2 nanosheets possessed a strong adsorption capacity for ssDNA, resulting in fluorescence quenching of FAM. After the addition of Hg2+ or Ag+, ssDNA formed double chains structure, the fluorescence recovered due to the weak adsorption capacity of MoS2 nanosheets for dsDNA. Along this line, an "off-on" mode fluorescence nanobiosensor was designed to alternatively detect these two heavy metal ions in water. The sensor showed high sensitivity and excellent selectivity for both Hg2+ and Ag+ ions, with minimum detection limits of 6.8 nM and 8.9 nM, respectively.

Bismuth oxyformate microspheres assembled by ultrathin nanosheets as an efficient negative material for aqueous alkali battery.

A negative electrode with high capacity and rate capability is essential to match the capacity of a positive electrode and maximize the overall charge storage performance of an aqueous alkali battery (AAB). Due to the 3-electron redox reactions within a wide negative potential range, bismuth (Bi)-based compounds are recognized as efficient negative electrode materials. Herein, hierarchically structured bismuth oxyformate (BiOCOOH) assembled by ultrathin nanosheets was prepared by a solvothermal reaction for application as negative material for AAB. Given the efficient ion diffusion channels and sufficient exposure of the inner surface area, as well as the pronounced 3-electron redox activity of Bi species, the BiOCOOH electrode offered a high specific capacity (Cs, 229 ± 4 mAh g-1 at 1 A g-1) and superior rate capability (198 ± 6 mAh g-1 at 10 A g-1) within 0 âˆ¼ -1 V. When pairing with the Ni3S2-MoS2 battery electrode, the AAB delivered a high energy density (Ecell, 217 mWh cm-2 at a power density (Pcell) of 661 mW cm-2), showing the potential of such a novel BiOCOOH negative material in battery-type charge storage.

Designing Hollow Carbon Sphere with Hierarchal Porous for Na-S Systems with Ultra-Long Cycling Stabilities.

Captured by the low-cost and high theoretical specific capacity, Na-S systems have garnered much attention. However, their intermediate products (dissolved polysulfide) are always out of control. Considering the excellent space confinements and conductivity, they have been regarded as promising candidates. Herein, the hollow spheres with suitable thickness shell (~20 nm) are designed as hosting materials, accompanied by in-depth complexing. Benefitting from the abundant micro-pores (mainly about conical-type and slits-type pores < 1.0 nm), the active S4 molecules are successfully filled in the pores through vacuum tube sealing technology, effectively avoiding the process from solid S8 to liquid Na2S6. As cathode for Na-S systems, their capacity could remain at 920 mAh g−1 at 0.1 C after 100 cycles. Even at 10.0 C, the capacity still remained at about 310 mAh g−1 after 7000 cycles. Supported by the detailed kinetic behaviors, the improvement of ions diffusion behaviors is noted, bringing about the effective thorough redox reactions. Moreover, the enhanced surface-controlling behaviors further induces the evolution of rate properties. Therefore, their stable phase changing is further confirmed through in situ resistances. Thus, the work is anticipated to offer significant design for hosting carbon materials and complexing manners.

Thermodynamic and Kinetic Binding Behaviors of Human Serum Albumin to Silver Nanoparticles.

A nanoparticle, under biological milieu, is inclined to be combined with various biomolecules, particularly protein, generating an interfacial corona which provides a new biological identity. Herein, the binding interaction between silver nanoparticles (AgNPs) and human serum albumin (HSA) was studied with transmission electron microscopy (TEM), circular dichroism (CD), and multiple spectroscopic techniques. Due to the ground state complex formed mainly through hydrophobic interactions, the fluorescence titration method proved that intrinsic fluorescence for HSA was probably statically quenched by AgNPs. The complete thermodynamic parameters were derived, indicating that the interaction between HSA and AgNPs is an entropy-driven process. Additionally, synchronous fluorescence and CD spectrum results suggested the conformational variation it has upon binding to AgNPs and the α-helix content has HSA visibly decreased. The kinetic experiments proved the double hysteresis effect has in HSA's binding to the AgNPs surface. Moreover, the binding has between HSA and AgNPs follows the pseudo-second-order kinetic characteristic and fits the Freundlich model for multilayer adsorption. These results facilitate the comprehension about NPs' underlying biological effects under a physiological environment and promote the secure applications of NPs biologically and medically.

Cathode materials for aqueous zinc-ion batteries: A mini review.

Although lithium-ion batteries (LIBs) have many advantages, they cannot satisfy the demands of numerous large energy storage industries owing to their high cost, low security, and low resource richness. Aqueous zinc-ion batteries (ZIBs) with low cost, high safety, and high synergistic efficiency have attracted an increasing amount of attention and are considered a promising choice to replace LIBs. However, the existing cathode materials for ZIBs have many shortcomings, such as poor electron and zinc ion conductivity and complex energy storage mechanisms. Thus, it is crucial to identify a cathode material with a stable structure, substantial limit, and suitability for ZIBs. In this review, several typical cathode materials for ZIBs employed in recent years and their detailed energy storage mechanisms are summarized, and various methods to enhance the electrochemical properties of ZIBs are briefly introduced. Finally, the existing problems and expected development directions of ZIBs are discussed.

SiOx Anode: From Fundamental Mechanism toward Industrial Application.

Silicon monoxide (SiO) has been explored and confirmed as a promising anode material of lithium-ion batteries. Compared with pure silicon, SiO possesses a more stable microstructure which makes better comprehensive electrochemical properties. However, the lithiation mechanism remains in dispute, and problems such as poor cyclability, unsatisfactory electrical conductivity, and low initial Coulombic efficiency (ICE) need to be addressed. Additionally, more attention needs to be paid on the internal relationship between electrochemical performances and structures. In this review, the different preparation processes, the derived microstructure of the SiOx , the corresponding lithiation mechanism, and electrochemical properties are summarized. Researches about disproportionation reaction which is regarded as a key point and other modifications are systematically introduced. Closely linked with structure, the advantages and disadvantages of various SiOx anode materials are summarized and analyzed, and the possible directions toward the practical applications of SiOx anode material are presented. In a word, from the preparation and reaction mechanism of the material to the modifications and future development, a complete and systematical review on SiOx anode is presented.

A Ge/Carbon Atomic-Scale Hybrid Anode Material: A Micro-Nano Gradient Porous Structure with High Cycling Stability.

The continuous growth of the solid-electrolyte interface (SEI) and material crushing are the fundamental issues that hinder the application of Ge anodes in lithium-ion batteries. Solving Ge deformation crushing during discharge/charge cycles is challenging using conventional carbon coating modification methods. Due to the chemical stability and high melting point of carbon (3500 °C), Ge/carbon hybridization at the atomic level is challenging. By selecting a suitable carbon source and introducing an active medium, we have achieved the Ge/carbon doping at the atom-level, and this Ge/carbon anode shows excellent electrochemical performance. The reversible capacity is maintained at 1127 mAh g-1 after 1000 cycles (2 A g-1 (2-71 cycles), 4 A g-1 (72-1000 cycles)) with a retention of 84 % compared to the second cycle. The thickness of the SEI is only 17.4 nm after 1000 cycles. The excellent electrochemical performance and stable SEI fully reflect the application potential of this material.

Inhibition of the shuttle effect of lithium-sulfur batteries via a tannic acid-metal one-step in situ chemical film-forming modified separator.

The dissolution of polysulfides in an electrolyte is a thermodynamically favorable process, which in theory means that the shuttle effect in lithium-sulfur batteries (LSBs) cannot be completely suppressed. So, it is very important to modify the separator to prevent the migration of polysulfides to the lithium anode. The traditional coating modification process of the separator is cumbersome and uses a solvent that is harmful to the environment, and too many inactive components affect the overall energy density of the battery. It is thus imperative to find a simple and environmentally friendly modification process of the separator. In this study, a fast chemical film-forming method is proposed to modify the separator of a lithium-sulfur battery using tannic acid (TA) and cobalt ions (Co2+). This method requires only simple steps and environmentally friendly raw materials to obtain a thin coating (only 5.83 nm) that can effectively inhibit the shuttle effect. The lithium-sulfur battery with the TA-Co separator shows superior long cycle performance. After 500 cycles at 0.5 C, the capacity decay rate of each cycle is only 0.065%. On the other hand, the TA-Co separator can inhibit the growth of lithium dendrites and help to build a stable lithium anode, which can exhibit minimal polarization (56 mV) in a lithium-lithium symmetrical battery at the current density of 2 mA cm-2. The rapid and simple modification method proposed in this study has a certain reference value for the future large-scale application of lithium sulfur batteries.

New Insights into the Mechanism of Enhanced Performance of Li[Ni0.8Co0.1Mn0.1]O2 with a Polyacrylic Acid-Modified Binder.

A binder is an important component in lithium-ion batteries and plays a significant role in maintaining the properties of active substances. Most studies in the field of binders have only focussed on physical properties such as bonding performance. Here, a polyacrylic acid-modified binder was designed and adapted to Li[Ni0.8Co0.1Mn0.1]O2, which enhanced the electrochemical stability of Li[Ni0.8Co0.1Mn0.1]O2 from 30.2 to 66.6% (300 cycles at 1 C). We for the first time discovered that this was caused by a chemical reaction between polyacrylic acid and the residual lithium on the surface during the cycling, which formed a lithium propionic acid coating layer and maintained the stability of the layered structure.

Simultaneous voltammetric determination of epinephrine and acetaminophen using a highly sensitive CoAl-OOH/reduced graphene oxide sensor in pharmaceutical samples and biological fluids.

For this study, three novel types of sensors comprised of CoAl-layered double oxyhydroxide (CoAl-LDH), CoAl-LDH/reduced graphene oxide (rGO), and CoAl-OOH/rGO nanosheets were successfully fabricated on glassy carbon electrodes (GCEs) and employed for the electrochemical detection of epinephrine (EP) and acetaminophen (AC). Interestingly, we found that the CoAl-OOH/rGO/GCE was more suitable for the determination of EP and AC in contrast to the CoAl-LDH and CoAl-OOH/rGO sensors. Differential pulse voltammetry results revealed that the CoAl-OOH/rGO/GCE delivered excellent electrocatalytic activity. The sensitivities and detection limits for the simultaneous measurement of EP and AC were 12.2 µA µM-1 cm-2, 0.023 µM L-1, and 4.87 µA µM-1 cm-2, 0.058 µM L-1, respectively. Especially, the as-obtained CoAl-OOH/rGO/GCE was successfully utilized for the detection in pharmaceutical samples and biological fluids with satisfactory results. Owing to its outstanding electrocatalytic activity and superior sensitivity, the CoAl-OOH/rGO/GCE could be beneficial to construct a promising electrochemical sensor for the detection of EP and AC.

Nickel-Rich Layered Cathode Materials for Lithium-Ion Batteries.

Nickel-rich layered transition metal oxides are considered as promising cathode candidates to construct next-generation lithium-ion batteries to satisfy the demands of electrical vehicles, because of the high energy density, low cost, and environment friendliness. However, some problems related to rate capability, structure stability, and safety still hamper their commercial application. In this Review, beginning with the relationships between the physicochemical properties and electrochemical performance, the underlying mechanisms of the capacity/voltage fade and the unstable structure of Ni-rich cathodes are deeply analyzed. Furthermore, the recent research progress of Ni-rich oxide cathode materials through element doping, surface modification, and structure tuning are summarized. Finally, this review concludes by discussing new insights to expand the field of Ni-rich oxides and promote practical applications.

Novel Bifunctional Separator with a Self-Assembled FeOOH/Coated g-C3N4/KB Bilayer in Lithium-Sulfur Batteries.

Separator modification with metal oxide and carbon composite recently has become a potential and competitive way to confine polysulfide diffusion and mitigate the shuttling effect. However, other modification methods also have an impact on the stability of the modified layer and the enhancement of electrochemical performance. Herein, we first design a novel bifunctional separator combined with one self-assembled FeOOH layer via a chemical way and one conductive g-C3N4/KB layer by physical coating. Different from directly coating the metal oxide and carbon composite on the separator, the self-assembled FeOOH layer is firmly formed on the PP separator, which enables the chemical capture of the soluble polysulfide and prohibit the shuttling effect. Then, the coated g-C3N4/KB layer is further introduced to greatly enhance the transportation of lithium ions and physically confine the migration of intermediates. As a result, the battery with this bifunctional separator (G-SFO) achieves outstanding rate capacities (1000, 901, and 802 mA h/g at 0.5, 1, and 2 C). After 900 cycles at 1 C, it also shows excellent long cycle performance, with relatively low fading (0.055%). This original fabrication will present a new and feasible strategy for fabricating a bifunctional separator with metal oxide and carbon material.

Hydrangea-Like CuS with Irreversible Amorphization Transition for High-Performance Sodium-Ion Storage.

Metal sulfides have been intensively investigated for efficient sodium-ion storage due to their high capacity. However, the mechanisms behind the reaction pathways and phase transformation are still unclear. Moreover, the effects of designed nanostructure on the electrochemical behaviors are rarely reported. Herein, a hydrangea-like CuS microsphere is prepared via a facile synthetic method and displays significantly enhanced rate and cycle performance. Unlike the traditional intercalation and conversion reactions, an irreversible amorphization process is evidenced and elucidated with the help of in situ high-resolution synchrotron radiation diffraction analyses, and transmission electron microscopy. The oriented (006) crystal plane growth of the primary CuS nanosheets provide more channels and adsorption sites for Na ions intercalation and the resultant low overpotential is beneficial for the amorphous Cu-S cluster, which is consistent with the density functional theory calculation. This study can offer new insights into the correlation between the atomic-scale phase transformation and macro-scale nanostructure design and open a new principle for the electrode materials' design.

Effects of gold nanoparticle morphologies on interactions with proteins.

In biological milieu, nanoparticles tend to bind with a variety of biomolecules, particularly proteins, thereby forming an interfacial corona that endows them with a new biological identity. A thorough understanding of these protein coronas is likely to provide insights into nanoparticle biodistribution and nanoparticle-mediated cytotoxicity, leading to the expansion of potential applications and the further elucidation of the biological impacts of nanoparticles in biomedical applications. Herein, three differently shaped AuNPs were synthesized, namely nanospheres (AuNSPs), nanorods (AuNRs), and nanostars (AuNSs). The effects of the morphologies of AuNPs on the structures and functions of adsorbed fibrinogen (FIB) and trypsin (Try) were investigated via circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR). Simultaneously, two different types of proteins were employed to investigate their influences on the stability and aggregation of AuNPs, using UV-vis absorption spectroscopy, transmission electron microscopy (TEM), microscale thermophoresis (MST), and dynamic light scattering (DLS). It was found that, compared to AuNSPs, the irregularly shaped AuNPs (e.g., AuNRs and AuNSs) had the capacity to induce greater changes in the secondary structures of the proteins. Furthermore, it appeared that the differently shaped AuNPs had obvious effects on the secondary structure of Try, and slight effects on the secondary structure of FIB. Consequently, these preliminary results indicated that the formation of protein corona, as well as the aggregation behaviors of the AuNPs was intimately related to the specific shapes of the AuNPs and the unique structures of the proteins.

Surface chemistry of gold nanoparticles determines interactions with bovine serum albumin.

Protein coronas provide a novel technique for the bio identification of nanoparticles in physiological environments, to further elucidate the biological effects of nanoparticles in biomedical applications. Herein, we investigated the adsorption of bovine serum albumin (BSA) on gold nanoparticles (AuNPs) with different surface modifications (citrate, cysteine, polyethylene glycol (PEG), and cetyltrimethylammonium bromide (CTAB)) using UV-vis absorption spectroscopy, fluorescence spectroscopy, circular dichroism (CD), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and transmission electron microscopy (TEM) techniques. It was revealed that the binding of AuNPs modified with citrate, cysteine, PEG (2k), and CTAB to BSA, appeared to be of the static quenching type, with binding constants in the range of from 108 to 1010 M-1. We also found that the conformation of BSA underwent various changes upon association with the different AuNP surface modifications. In addition, the preliminary results indicated that the thicknesses of protein coronas and the aggregation behaviors of AuNPs were closely related to their surface properties. These findings offered important insights into the essence of the interactions between nanoparticles and proteins toward the development of safe and effective nanomaterials in biological systems.

DNA-functionalized gold nanoparticle-based fluorescence polarization for the sensitive detection of silver ions.

Despite their practical applications, Ag+ ions are environmental pollutants and affect human health. So the effective detection methods of Ag+ ions are imperative. Herein, we developed a simple, sensitive, selective, and cost-effective fluorescence polarization sensor for Ag+ detection in aqueous solution using thiol-DNA-functionalized gold nanoparticles (AuNPs). In this sensing strategy, Ag+ ions can specifically interact with a cytosine-cytosine (CC) mismatch in DNA duplexes and form stable metal-mediated cytosine-Ag+-cytosine (C-Ag+-C) base pairs. The formation of the C-Ag+-C complex results in evident changes in the molecular volume and fluorescence polarization signal. To achieve our aims, we prepared two complementary DNA strands containing C-base mismatches (probe A: 5'-SH-A10-TACCACTCCTCAC-3' and probe B: 5'-TCCTCACCAGTCCTA-FAM-3'). The stable hybridization between probe A and probe B occurs with the formation of the C-Ag+-C complex in the presence of Ag+ ions, leading to obvious fluorescence quenching in comparison to the system without AuNP enhancement. The assay can be used to identify nanomolar levels of Ag+ within 6 min at room temperature, and has extremely high specificity for Ag+, even in the presence of higher concentrations of interfering metal ions. Furthermore, the sensor was successfully applied to the detection of Ag+ ions in environmental water samples and showed excellent selectivity and high sensitivity, implying its promising application in the future.

Exploring the interaction of silver nanoparticles with lysozyme: Binding behaviors and kinetics.

The role of nanoparticle interaction with biomolecules to form a biocorona is the key to nanoparticle behavior and its consequences in the physiological environment. Since the adsorbed biocorona decides the fate of a nanomaterials in vivo, and thus a comprehensive understanding of the dynamic interactions of the proteins with the nanoparticle is imperative. Herein we investigate the interaction of a model protein, lysozyme with silver nanoparticles (AgNPs) using fluorescence, synchronous fluorescence, UV-vis absorption spectrum and circular dichroism (CD) techniques under the physiological conditions. The results indicated that the binding of AgNPs to lysozyme may be a static quenching mechanism. With the analysis of the fluorescence spectral data, the binding constants and the thermodynamic parameters were determined, which suggests that the binding of AgNPs to lysozyme is a spontaneous process. Moreover, it was demonstrated that the main acting forces between AgNPs and lysozyme may be hydrophobic interactions. At the same time, the conformational change of lysozyme induced by AgNPs was investigated with synchronous fluorescence spectroscopy and CD techniques. The results of kinetic studies reveal that the adsorption of lysozyme on AgNPs surface tends to follow pseudo-second-order kinetic characteristic with obvious hysteresis effect.

Probing the binding of trypsin to glutathione-stabilized gold nanoparticles in aqueous solution.

We investigate the interaction of trypsin with glutathione-stabilized Au nanoparticles (NPs) using fluorescence, synchronous fluorescence and ultraviolet (UV) absorption spectroscopy. We find that trypsin binds strongly to the Au NPs with a static quenching mechanism, and that the interaction is characteristic of positive cooperative binding. Furthermore, we determine the binding constants and the thermodynamic parameters, which suggest that the main binding forces between the glutathione-stabilized Au NPs and trypsin are electrostatic interactions and hydrogen bonding. Analysis of UV-vis absorption spectra suggests that aggregation of the Au NPs occurs in the trypsin/Au NPs system, which significantly alters the conformation of the protein.