Showing papers on "Chemical binding published in 2021"

Tunable Electrocatalytic Behavior of Sodiated MoS 2 Active Sites toward Efficient Sulfur Redox Reactions in Room-Temperature Na-S Batteries.

Abstract: Room-temperature (RT) sodium-sulfur (Na-S) batteries hold great promise for large-scale energy storage due to the advantages of high energy density, low cost, and resource abundance. The research progress on RT Na-S batteries, however, has been greatly hindered by the sluggish kinetics of the sulfur redox reactions. Herein, an elaborate multifunctional architecture, consisting of N-doped carbon skeletons and tunable MoS2 sulfiphilic sites, is fabricated via a simple one-pot reaction followed by in situ sulfurization. Beyond the physical confinement and chemical binding of polarized N-doped carbonaceous microflowers, the MoS2 active sites play a key role in catalyzing polysulfide redox reactions, especially the conversion from long-chain Na2 Sn (4 ≤ n ≤ 8) to short-chain Na2 S2 and Na2 S. Significantly, the electrocatalytic activity of MoS2 can be tunable via adjusting the discharge depth. It is remarkable that the sodiated MoS2 exhibits much stronger binding energy and electrocatalytic behavior compared to MoS2 sites, effectively enhancing the formation of the final Na2 S product. Consequently, the S cathode achieves superior electrochemical performance in RT Na-S batteries, delivering a high capacity of 774.2 mAh g-1 after 800 cycles at 0.2 A g-1 , and an ultrahigh capacity retention with a capacity decay rate of only 0.0055% per cycle over 2800 cycles.

Optimizing Surface Chemistry of PbS Colloidal Quantum Dot for Highly Efficient and Stable Solar Cells via Chemical Binding.

Abstract: The surface chemistry of colloidal quantum dots (CQD) play a crucial role in fabricating highly efficient and stable solar cells. However, as-synthesized PbS CQDs are significantly off-stoichiometric and contain inhomogeneously distributed S and Pb atoms at the surface, which results in undercharged Pb atoms, dangling bonds of S atoms and uncapped sites, thus causing surface trap states. Moreover, conventional ligand exchange processes cannot efficiently eliminate these undesired atom configurations and defect sites. Here, potassium triiodide (KI3) additives are combined with conventional PbX2 matrix ligands to simultaneously eliminate the undercharged Pb species and dangling S sites via reacting with molecular I2 generated from the reversible reaction KI3 ⇌ I2 + KI. Meanwhile, high surface coverage shells on PbS CQDs are built via PbX2 and KI ligands. The implementation of KI3 additives remarkably suppresses the surface trap states and enhances the device stability due to the surface chemistry optimization. The resultant solar cells achieve the best power convention efficiency of 12.1% and retain 94% of its initial efficiency under 20 h continuous operation in air, while the control devices with KI additive deliver an efficiency of 11.0% and retains 87% of their initial efficiency under the same conditions.

Embedding Fe3C and Fe3N on a Nitrogen-Doped Carbon Nanotube as a Catalytic and Anchoring Center for a High-Areal-Capacity Li-S Battery.

Abstract: The biggest obstacles of putting lithium-sulfur batteries into practice are the sluggish redox kinetics of polysulfides and serious "shuttle effect" under high sulfur mass loading and lean-electrolyte conditions. Herein, Fe3C/Fe3N@nitrogen-doped carbon nanotubes (NCNTs) as multifunctional sulfur hosts are designed to realize high-areal-capacity Li-S batteries. The Fe3N and Fe3C particles attached to NCNT can promote the conversion of polysulfides. Besides, NCNT can not only enhance the chemisorption of polysulfides but also increase the special surface area and electrical conductivity by constructing a three-dimensional skeleton network. Integrating the merits of high electrical conductivity, high catalytic activity, and strong chemical binding interaction with lithium polysulfides (LiPSs) to achieve in situ anchoring conversion, the Fe3C/Fe3N@NCNT multifunctional hosts realize high sulfur mass loading and accelerate redox kinetics. The novel Fe3C/Fe3N@NCNT/S composite cathode exhibits steady cycle ability and a high areal capacity of 9.10 mAh cm-2 with a sulfur loading of 13.12 mg cm-2 at 2.20 mA cm-2 after 50 cycles.

Lewis Base Passivation Mediates Charge Transfer at Perovskite Heterojunctions.

Abstract: Understanding interfacial charge transfer processes such as trap-mediated recombination and injection into charge transport layers (CTLs) is crucial for the improvement of perovskite solar cells. Herein, we reveal that the chemical binding of charge transport layers to CH3NH3PbI3 defect sites is an integral part of the interfacial charge injection mechanism in both n-i-p and p-i-n architectures. Specifically, we use a mixture of optical and X-ray photoelectron spectroscopy to show that binding interactions occur via Lewis base interactions between electron-donating moieties on hole transport layers and the CH3NH3PbI3 surface. We then correlate the extent of binding with an improvement in the yield and longer lifetime of injected holes with transient absorption spectroscopy. Our results show that passivation-mediated charge transfer has been occurring undetected in some of the most common perovskite configurations and elucidate a key design rule for the chemical structure of next-generation CTLs.

Reduction of Nonradiative Loss in Inverted Perovskite Solar Cells by Donor-π-Acceptor Dipoles.

Abstract: Inverted perovskite solar cells (IPSCs) attract growing interest because of their simple configuration, reliable stability, and compatibility with tandem applications. However, the power conversion efficiency (PCE) of IPSCs still lags behind their regular counterparts, mainly due to the more serious nonradiative loss. Here, we design three donor-π-acceptor (D-π-A) dipoles with various dipole moments to introduce extra electric fields at the interface of perovskites and electron transport materials via the binding between the carboxylate end group and under-coordinated divalent Pb. The chemical binding reduces the recombination centers, while the superposition of the built-in electric field facilitates the electron collection and the hole blocking. As a result, the nonradiative loss is diminished as the dipole moments of D-π-A dipoles increase, which contributes to a PCE of 21.4% with enhancement in both the open-circuit voltage and fill factor. The stability for an unencapsulated device is also improved due to the hydrophobic property of D-π-A dipoles.

Suppressing Redox Shuttle with MXene-Modified Separators for Li-O2 Batteries.

Abstract: Redox mediators (RMs) have been developed as efficient approaches to lower the charge polarization of Li-O2 batteries. However, the shuttle effect resulting from their soluble nature severely damages the battery performance, causing failure of the RM and anode corrosion. In this work, a chemical binding strategy based on a MXene-modified separator with a 3D porous hierarchical structure design was developed to suppress the I3- shutting in LiI-involved Li-O2 battery. As corroborated by experimental characterizations and theoretical calculations, the abundant -OH terminal groups on the MXene surface functioned as effective binding sites for suppressing the migration of I3-, while the 3D porous structure ensured the fast transfer of lithium ions. As a result, the Li-O2 battery with the MXene-modified separator showed no sign of redox shuttling compared with its counterparts in the full discharge/charge tests. In the meantime, the MXene-modified separator based-cell exhibited a stable cycle life up to 100 cycles, which is 3 times longer than the control samples. We believe that this work could provide insights into the development of separator modification for Li-O2 batteries with RMs.

Environmentally friendly magnetic chitosan nano-biocomposite for Cu(II) ions adsorption and magnetic nano-fluid hyperthermia: CCD-RSM design

Abstract: Chitosan conjugated superparamagnetic iron oxide nanoparticle stabilized citric acid (SPION-CA-CH) nano-biocomposite was fabricated in three synthetic steps; Synthesis of SPION, SPION's surface stabilization with citric acid, and its surface modification with chitosan via carbodiimide chemical reaction. This chemical binding has made it an environmentally clean and biocompatible candidate for magnetically targeting applications. The high performance of the SPION-CA-CH examined through two applications; first, performing as a nano-adsorbent for adsorption of Cu(II) ions as a heavy metal model, and secondly, as targeted nano-heaters for magnetic nano-fluid hyperthermia (MNFH). RSM applied for optimizing and modeling parameters. From the RSM model, the optimum experimental conditions to achieve 91.3% removal of Cu(II) ions were at pH 6.54, nano-adsorbent concentration 0.92 g L−1, and contact time 65.7 min. The maximum Langmuir adsorption capacity was 232.55 mg g−1 (R2=0.9992). Besides, the equilibrium data were well described, with the pseudo-second-order kinetic (R2=0.9993). Desorption studies displayed that the adsorption capacity of prepared nano-adsorbent decreased 12.5% after five times reuse, indicating efficient recovery of the nano-adsorbent for practical application. Apart from the adsorption application, we evaluated the potential of the SPION-CA-CH for MNFH. Optimum conditions for a maximum specific absorption rate (SAR) of 184.40 W g−1 were at 27 kA m−1 and the nano-heater concentration of 1.00 mg mL−1. All in all, the high magnetic response (Ms=60.4 emu g−1), adsorption capacity, reusability, and SAR value, make SPION-CA-CH a potential magnetic nano-adsorbent in wastewater treatment and nano-heaters for MNFH treatment technology.

Unveiling the physiochemical aspects of the matrix in improving sulfur-loading for room-temperature sodium–sulfur batteries

Abstract: The sulfur cathode in Na/S batteries possesses a very high theoretical specific capacity of about 1675 mA h g−1 and specific energy of 1230 W h kg−1 (which is over five times that of the LiCoO2 cathode in Li-ion batteries), besides high abundance and cost-effectiveness of the electrode materials. The sulfur cathode in Na/S batteries undergoes various electrochemical processes, where a series of soluble sodium polysulfides are formed during the discharge reaction, which adversely affects the operation of the cell. Furthermore, the viable application of RT-Na/S batteries is severely challenged by various obstacles, including their short-life and low-sulfur utilization, which become more serious when sulfur loading is increased to the practically acceptable level of over 5 mg cm−2. Thus, there have been innovative efforts in recent years to manipulate the physiochemistry of the matrix to overcome these barriers toward the practical application of RT-Na/S batteries with an improved sulfur loading close to practical limits. The rational design of the matrix (i.e., physicochemical aspects) with a high-sulfur utilization and long lifespan are two crucial challenges that Na/S batteries are experiencing currently and require immediate attention to be addressed. This review highlights the recent progress on tuning the physiochemistry of the matrix through chemical and physical means to realize an improved sulfur-loading. Particularly, basic insight into the chemical binding, strategies for mesoscale assembly, unique architectures, and configurational innovation in the cathode are the specific focus. Finally, novel strategies to improve sulfur-loading are proposed to guide the future development of high-sulfur loading RT-Na/S batteries.

Selectively Desirable Rapeseed and Corn Stalks Distinctive for Low-Cost Bioethanol Production and High-Active Biosorbents

Abstract: Crop straws provide large amounts of biomass resource for biofuels, but it remains to explore cost-effective lignocellulose process technology with additional valuable bioproducts. Using total eight rapeseed and corn stalks with distinct lignocellulose composition, this study initially performed mild alkali pretreatment (1% NaOH, 50 °C) for enzymatic hydrolysis and yeast fermentation to release bioethanol yields varied from 5 to 12% (% dry matter). By comparison, four corn stalks consistently showed more ethanol yields than those of the rapeseeds, but relatively higher sugar-ethanol conversion rates were examined in the rapeseed samples. Of all stalk samples, both genetic corn mutant (CY04) and classic rapeseed cultivar (Bn18) were respectively assessed as the desired lignocellulose residues for relatively high bioethanol production. Then, all remained solid residues of yeast fermentation were employed as biosorbents for Cd adsorption under various incubation conditions (pH, temperature, time, Cd concentration, biosorbent dose). In general, the solid residues exhibited much higher Cd adsorption capacities and removal rates than those of the raw stalks. In particular, two desirable rapeseed residues were of the highest Cd adsorption capacities, compared to the corn residues examined in this study or other major agricultural crop straws as previously reported. Furthermore, the solid residues were characterized as typical biosorbents via a classic chemical binding manner with much large surface areas accountable for their high Cd adsorption capacity. Therefore, this study has demonstrated a green-like strategy for low-cost cellulosic ethanol production and high-active biosorbents by selecting desired corn and rapeseed stalks.

MSA-Regularized Protein Sequence Transformer toward Predicting Genome-Wide Chemical-Protein Interactions: Application to GPCRome Deorphanization.

Abstract: Small molecules play a critical role in modulating biological systems. Knowledge of chemical-protein interactions helps address fundamental and practical questions in biology and medicine. However, with the rapid emergence of newly sequenced genes, the endogenous or surrogate ligands of a vast number of proteins remain unknown. Homology modeling and machine learning are two major methods for assigning new ligands to a protein but mostly fail when sequence homology between an unannotated protein and those with known functions or structures is low. In this study, we develop a new deep learning framework to predict chemical binding to evolutionary divergent unannotated proteins, whose ligand cannot be reliably predicted by existing methods. By incorporating evolutionary information into self-supervised learning of unlabeled protein sequences, we develop a novel method, distilled sequence alignment embedding (DISAE), for the protein sequence representation. DISAE can utilize all protein sequences and their multiple sequence alignment (MSA) to capture functional relationships between proteins without the knowledge of their structure and function. Followed by the DISAE pretraining, we devise a module-based fine-tuning strategy for the supervised learning of chemical-protein interactions. In the benchmark studies, DISAE significantly improves the generalizability of machine learning models and outperforms the state-of-the-art methods by a large margin. Comprehensive ablation studies suggest that the use of MSA, sequence distillation, and triplet pretraining critically contributes to the success of DISAE. The interpretability analysis of DISAE suggests that it learns biologically meaningful information. We further use DISAE to assign ligands to human orphan G-protein coupled receptors (GPCRs) and to cluster the human GPCRome by integrating their phylogenetic and ligand relationships. The promising results of DISAE open an avenue for exploring the chemical landscape of entire sequenced genomes.

Inorganic Materials for Regenerative Medicine

Abstract: Methods that are used in regenerative medicine rely on the inherent ability of living organisms to regenerate their tissue. If the size (volume) of a defect exceeds some critical level, regeneration can be initiated and maintained using resorbable porous scaffolds made of natural, artificial, or synthetic materials capable of temporary defect compensation. When modified with pharmaceutical products and specific proteins or cells, such porous scaffolds are referred to as tissue engineering constructs. Inorganic resorbable materials are most frequently used for bone tissue defect repair. Natural bone is a composite having a polymer (collagen) matrix filled with calcium phosphate nanocrystals in the form of insoluble calcium hydroxyapatite. For this reason, calcium phosphate-based materials are leaders of medical inorganic materials research. To date, resorbable biocompatible materials based on tricalcium phosphate, calcium pyrophosphate, brushite, monetite, and octacalcium phosphate have been developed. Calcium hydroxyapatite is known as an inorganic ion exchanger. Because of this, the composition of bone tissue includes, in addition to phosphate and calcium ions, carbonate, silicate, and sulfate ions, as well as sodium, potassium, magnesium, iron, strontium, zinc and some other metal ions. The fact that bone tissue contains anions substituting for orthophosphate ions or hydroxide ions in the calcium hydroxyapatite of bone tissue prompted researchers to produce resorbable materials based on calcium sulfates, calcium carbonate, and calcium phosphates in which orthophosphate ions are replaced by anions mentioned above. Cation substitutions in calcium hydroxyapatite of bone tissue and the chemical composition of the medium of an organism allow one to produce and use resorbable materials for bone implants consisting of cation-substituted calcium phosphates and calcium–biocompatible cation double phosphates, such as sodium-substituted tricalcium phosphate, potassium-substituted tricalcium phosphate, sodium rhenanite, potassium rhenanite, and calcium magnesium double pyrophosphate. The resorption of an inorganic material intended for use as a pharmaceutical product can be controlled via designing a preset phase composition. The above-mentioned biocompatible resorbable phases can be used in various combinations in already existing composite materials or composites under development. The microstructure of a biocompatible resorbable inorganic material can be formed as a result of various physicochemical processes. The phase composition and microstructure of a ceramic material are determined by solid-state and liquid-phase sintering processes, as well as by heterogeneous chemical reactions during firing. The phase composition and microstructure of cement stone are formed as a result of chemical binding reactions initiated by the addition of water or aqueous solutions. Amorphous materials can be prepared via melting of starting reagents or sol–gel processing. The osteoconductivity of a biocompatible resorbable inorganic material is an important property necessary for body fluids and bone cells to be able to penetrate into the implant material. Macroporosity, which determines the osteoconductivity of a resorbable inorganic material, can be produced using various technological approaches. 3D printing methods make it possible to obtain materials with tailored phase composition and microstructure and permeable macroporosity of preset architecture. A large surface area of a porous inorganic material is thought to be a factor of controlling the resorption rate. This review summarizes information about existing biocompatible resorbable inorganic materials for regenerative medicine and considers physicochemical principles of the preparation of such materials with the use of synthetic starting powders and natural materials.

Portable Automatic Microring Resonator System Using a Subwavelength Grating Metamaterial Waveguide for High-Sensitivity Real-Time Optical-Biosensing Applications

Abstract: The slow light sensor techniques have been applied to bio-related detection in the past decades. However, similar testing-systems are too large to carry to a remote area for diagnosis or point-of-care testing. This study demonstrated a fully automatic portable biosensing system based on the microring resonator. An optical-fiber array mounted on a controller based micro-positioning system, which can be interfaced with MATLAB to locate a tentative position for light source and waveguide coupling alignment. Chip adapter and microfluidic channel could be packaged as a product such that it is cheap to be manufactured and can be disposed of after every test conducted. Thus, the platform can be more easily operated via an ordinary user without expertise in photonics. It is designed based on conventional optical communication wavelength range. The C-band superluminescent-light-emitting-diode light source couples in/out the microring sensor to obtain quasi-TE mode by grating coupler techniques. For keeping a stable chemical binding reaction, the cost-effective microfluidic pump was developed to offer a specific flow rate of 20 μL/min by using a servo-motor, an Arduino board, and a motor driver. The subwavelength grating metamaterial ring resonator shows highly sensitive sensing performance via surface index changes due to biomarker adhered on the sensor. The real-time peak-shift monitoring shows 10 μg/mL streptavidin detection of limit based on the biotin-streptavidin binding reaction. Through the different specific receptors immobilized on the sensor surface, the system can be utilized on the open applications such as heavy metal detection, gas sensing, virus examination, and cancer marker diagnosis.

Investigating the in vitro photothermal effect of green synthesized apigenin-coated gold nanoparticle on colorectal carcinoma.

Abstract: Applying toxic chemical to the synthesis of stable gold nanoparticles is one of the limitations of gold nanoparticles for therapeutic applications such as photothermal therapy. Plant compounds such as apigenin (API) with therapeutic potential can be applied in the synthesis of gold nanoparticles. API-coated gold nanoparticles (Api@AuNPs) with an average size of 19.1 nm and a surface charge of -4.3 mV have been synthesized by a simple and efficient technique. The stability of Api@AuNPs in the biological environment was verified through UV-Vis spectroscopy. Based on Raman and FTIR spectroscopy analysis, chemical binding of API on the surface of Api@AuNPs through hydroxyl and carbonyl functional groups was found to be the main reason for the stability of the Api@AuNPs in comparison with citrate-coated gold nanoparticles (Cit@AuNPs). The synthesized Api@AuNPs do not cause major toxic effects up to 128 ppm. Api@AuNP-mediated photothermal therapy leads to the indiscriminate eradication of almost half of both mouse fibroblastic (L929) and colorectal cancer (CT26) cells. Flow-cytometry analysis revealed that the cell death mechanism is mainly apoptosis. In the apoptosis triggered cell death in photothermal treatment, Api@AuNPs are preferred over commonly used gold nanoparticles in photothermal treatments which mostly trigger the necrosis cell death pathway.

Chemical binding of horseradish peroxidase enzyme with poly beta‐cyclodextrin and its application as molecularly imprinted polymer for the monitoring of H 2 O 2 in human plasma samples

Abstract: In this study, a selective and sensitive molecular imprinting-based electrochemical sensors, for horseradish peroxidase (HRP) entrapment was fabricated using electro polymerization of s-Cyclodextrin (s-CD) on the surface of glassy carbon electrode. Poly beta-cyclodextrin P(s-CD) provide efficient surface area for self-immobilization of HRP as well as improve imprinting efficiency. The proposed imprinted biosensor successfully utilized for detection of HRP with excellent analytical results which linear range is 0.1 mg/mL to 10 ng/mL with LOD of 2.23 ng/mL. Furthermore, electrocatalytical activity of the prepared biosensor toward the reduction of hydrogen peroxide was investigated in the ranges of 1 to 15 μM with a detection limit of 0.4 μM by using chronoamperometry technique. The developed biosensor was used for the detection of hydrogen peroxide in unprocessed human plasma sample.

Chloride permeability and chloride binding capacity of nano-modified concrete

Abstract: Chloride permeability and chloride binding capacity are two important factors for assessment of the rebar corrosion risk in reinforced concrete structures . In this work, the chloride permeability and chloride binding capacity of concrete modified with nano-SiO 2 (NS), nano-CaCO3 (NC), multi-walled carbon nanotubes (CNT) were evaluated. The results demonstrate that incorporation of nanomaterials significantly decreases the chloride diffusion coefficients by refining the pore structure and reducing the pore volume. The experimental data strongly suggest the existence of a percolation threshold (critical porosity), below which the chloride permeability decreases dramatically. Addition of NS compromises the chloride binding capacity due to decreased pH value of pore solution , which results in dissolution of Friedel's salt. XRD suggests that adding NC restrains the formation of AFm phase, which is mainly responsible for the chemical binding. TG/DTG analyses confirm that adding CNT facilitates the formation of more amount of hydrates, thus enhancing the chloride binding. Addition of NS and NC leads to a decreased amount of Friedel's salt and thereby weakens the chemical binding.