Base Chemistry Research Articles

Sustainable Green Solvents for Lead Halide Perovskites

AbstractLead halide perovskites have revolutionized the field of optoelectronics and attracted worldwide attention due to their outstanding semiconducting characteristics. Meanwhile, solution processability and printability of the perovskite allow the commercialization of perovskite solar cells (PSCs) profitable. However, deposition of the perovskite films usually uses polar aprotic solvents. The popular antisolvents are aromatics or aromatic halogenated hydrocarbons. All of them have a high risk of toxicity and flammability. To reduce the adverse effects on the environment and operators and enhance the sustainability of perovskite technologies, researchers have made lots of efforts to study sustainable green solvents. Herein, the selection criteria of green solvents are surveyed. Methods of solubility prediction of precursor solvents are comprehensively discussed from the perspectives of polarity and Lewis acid–base chemistry. The significance of antisolvent polarity and boiling point is emphasized. Research advances in green solvents are summarized. Finally, this review presents in‐depth insights into green‐solvent‐processable perovskites and highlights research directions for perovskite modules in the future. It lays a good foundation for the commercialization and sustainable development of PSCs.

Microenvironment‐Responsive Injectable Conductive Hydrogel for Spinal Cord Injury Repair

AbstractSpinal cord injury (SCI) represents a severe neurological condition often coupled with a drastic secondary inflammatory response, which further exacerbates the damage in most cases. Due to their unique electrical and mechanical compatibilities with the spinal cord, the utilization of conductive hydrogels through injection for SCI repair, particularly in scenarios involving non‐uniform and large gaps, has emerged as a promising approach. Herein, leveraging the acidic microenvironment characteristic of acute SCI sites, an injectable conductive hydrogel with pH‐responsive immunoregulation is engineered for SCI repair. Based on the dynamic Schiff base chemistry and covalent photo‐crosslinking, this composite hydrogel, composed of gelatin methacryloyl, oxidized dextran, and MoS2, exhibits adjustable mechanical and conductive properties, enabling a customized match with the natural spinal cord's attributes. Additionally, the incorporation of Wnt5a and its selective release in acidic conditions prompt the immediate suppression of inflammatory factors and enhances neural differentiation and regeneration. In the 2‐mm hemisection mouse SCI model, the optimized conductive hydrogel can effectively bridge the injury gap, establish nerve connections and signal, mitigate inflammatory response, and promoted recovery of mobility. This novel injectable conductive hydrogel system offers a promising advance in therapeutic materials for SCI repair.

Measurement report: Occurrence of aminiums in PM2.5 during winter in China – aminium outbreak during polluted episodes and potential constraints

Abstract. Amines and aminiums play an important role in particle formation, liquid-phase reactions, and climate change and have attracted considerable attention over the years. Here, we investigated the concentrations and compositions of aminiums in PM2.5 in 11 Chinese cities during the winter, focusing on the characteristics of aminiums during the polluted days and the key factors influencing aminium outbreak. Monomethylaminium was the dominant aminium species in most cities, except Taiyuan and Guangzhou, followed by dimethylaminium. Diethylaminium dominated the total aminiums in Taiyuan and Guangzhou. Thus, the main amine sources in Taiyuan and Guangzhou were significantly different from those in other cities. The concentrations of the total aminiums (TAs) in most cities increased significantly during the polluted days, while relatively weak aminium outbreaks during the polluted days occurred in Xi'an and Beijing. Additionally, the concentrations of TAs in Xi'an and Beijing were insignificantly correlated with those of PM2.5 and the major acidic aerosol components, while the opposite pattern was observed in nine other cities. Thus, acid–base chemistry was significantly associated with the formation of aminiums in PM2.5 in all cities, except Xi'an and Beijing. Based on the sensitivity analysis of the aminiums : ammonium ratio to ammonium changes, as well as excluding the effects of relative humidity and atmospheric oxidation, we proposed the possibility of the competitive uptake of ammonia versus amines on acidic aerosols or the displacement of aminiums by ammonia in Xi'an and Beijing (constraining aminium outbreaks). Overall, this study deepens the understanding of the spatiotemporal differences in aminium characteristic and formation in China. However, the uptake of amines on particles to form aminiums and the relevant influencing factors require further mechanistic research.

Exploring the potential of end-capping acceptor designing on highly soluble and efficient Schiff-based Hole-Transporting materials for High-Efficiency perovskite solar cells

Photovoltaic materials, especially perovskite solar cells (PSCs) are promising candidates for rising global energy demands. Here, five phenothiazine-based hole-transporting materials (AZOM1, AZOM2, AZOM3, AZOM4, and AZOM5) are designed by Schiff base chemistry with A-π-D-π-A framework for PSCs. We executed density functional theory calculations to explore the electronic, photo-physical, photovoltaic, and charge-transporting properties of the studied hole-transporting materials (HTMs). Our results indicate that AZOM1-AZOM5 HTMs possess more negativeHOMO energies (−5.64 to − 5.49 eV), lower bandgaps, and superior solubility as compared to Spiro-OMeTAD (HOMO energy = − 4.47 eV) and reference AZO-II (HOMO energy = − 4.68 eV), which enhanced their hole extraction and open-circuit photo-voltage (VOC). The transition density matrix and hole-electron distribution analyses show that AZOM1- AZOM5 molecules have ultrafast charge transmission, low overlapping between holes and electrons, and a higher dissociation rate than the Spiro-OMeTAD and AZO-II HTMs. The designed HTMs have smaller exciton binding energies than the Spiro-OMeTAD and AZO-II, allowing electron-hole pairs to dissociate into positive and negative charges smoothly. AZOM1-AZOM5 HTMs have higher hole charge transfer integral than the AZO-II, facilitating high hole mobility in PSCs. All designed HTMs have higher VOC (1.49 to 1.64 V) and lower energy losses (0.63 to 1.03 eV) than the Spiro-OMeTAD and AZO-II HTMs. Moreover, the AZOM1-AZOM5 HTMs demonstrated deeper HOMO energies, high solubility, more stability, and high open-circuit photo-voltages than the recently reported HTMs at “MPW1PW91/6-31G (d, p)” level of theory. Overall, the AZOM1-AZOM5 HTMs are very effective in boosting the solubility, charge-transporting ability, and efficiency of PSCs.

Surface Immobilization of Oxidized Carboxymethyl Cellulose on Polyurethane for Sustained Drug Delivery.

Polyurethane (PU) has a diverse array of customized physical, chemical, mechanical, and structural characteristics, rendering it a superb option for biomedical applications. The current study involves modifying the polyurethane surface by the process of aminolysis (aminolyzed polyurethane; PU-A), followed by covalently immobilizing Carboxymethyl cellulose (CMC)polymer utilizing Schiff base chemistry. Oxidation of CMC periodically leads to the creation of dialdehyde groups along the CMC chain. When the aldehyde groups on the OCMC contact the amine group on a modified PU surface, they form an imine bond. Scanning electron microscopy (SEM), contact angle, and X-ray photoelectron spectroscopy (XPS) techniques are employed to analyze and confirm the immobilization of OCMC on aminolyzed PU film (PU-O). The OCMC gel incorporates Nitrofurantoin (NF) and immobilizes it on the PU surface (PU-ON), creating an antibacterial PU surface. The confirmation of medication incorporation is achieved using EDX analysis. The varying doses of NF have demonstrated concentration-dependent bacteriostatic and bactericidal effects on both Gram-positive and Gram-negative bacteria, in addition to sustained release. The proposed polyurethane (PU-ON) surface exhibited excellent infection resistance in in vivo testing. The material exhibited biocompatibility and is well-suited for biomedical applications.

High-performance glued-bamboo through activation of chemical bonding interface

Bamboo glue products are widely used in decoration, construction and transportation. Bamboo is fast growing, strong and inexpensive, making it one of the ideal processing materials to replace steel and wood. Here we present a process for the production of high performance bamboo glue products. In this process, the conversion of natural bamboo surface (NBS) to oxidized bamboo surface (OBS) is a critical step prior to hot pressing, as it provides the bamboo interface with active sites (aldehyde groups) for chemical cross-linking with the adhesive. Subsequent covalent crosslinking with branched chain amine (PAXN) compounds is based on Schiff base chemistry. The improved properties of the oxidized bamboo specimens were attributed to chemical cross-linking within the oxidized bamboo-binder interface (OBI-PAXN) and further densification of the bamboo adhesive interface. The dry/hot/boiling water bond strength of OBI-PA6 N was increased by 130 % (7.5 MPa)/148 % (5.05 MPa)/130 % (3.26 MPa) compared to NBI-PA6 N (3.26 MPa, 2.04 MPa, 0.88 MPa). Its bonding strength and bending strength are superior to commercial PF resins. The combination of excellent mechanical properties with the rich, renewable and sustainable nature of bamboo makes it very attractive for engineering applications.

Improved characterization of single-cell RNA-seq libraries with paired-end avidity sequencing.

Prevailing poly(dT)-primed 3' single-cell RNA-seq protocols generate barcoded cDNA fragments containing the reverse transcriptase priming site, which is expected to be the poly(A) tail or a genomic adenine homopolymer. Direct sequencing across this priming site was historically difficult because of DNA sequencing errors induced by the homopolymeric primer at the 'barcode' end. Here, we evaluate the capability of "avidity base chemistry" DNA sequencing from Element Biosciences to sequence through this homopolymer accurately, and the impact of the additional cDNA sequence on read alignment and precise quantification of polyadenylation site usage. We find that the Element Aviti instrument sequences through the thymine homopolymer into the subsequent cDNA sequence without detectable loss of accuracy. The resulting paired-end alignments enable direct and independent assignment of reads to polyadenylation sites, which bypasses complexities and limitations of conventional approaches but does not consistently improve read mapping rates compared to single-end alignment. We also characterize low-level artifacts and arrive at an adjusted adapter trimming and alignment workflow that significantly improves the alignment of sequence data from Element and Illumina, particularly in the context of extended read lengths. Our analyses confirm that Element avidity sequencing is an effective alternative to Illumina sequencing for standard single-cell RNA-seq, particularly for polyadenylation site analyses but do not rule out the potential for similar performance from other emerging platforms.

Crafting Chemical Art with Safflower Extract: Home-based Acid–Base Chemistry and Spectrochemistry During Holidays

Crafting Chemical Art with Safflower Extract: Home-based Acid–Base Chemistry and Spectrochemistry During Holidays

Substituent engineering in tertiary phosphine oxides for passivating defects of perovskite solar cells

AbstractDefect passivation based on Lewis acid–base chemistry has been regarded as an effective strategy to improve the photovoltaic performance and stability of perovskite solar cells (PSCs). Here, we report on tertiary phosphine oxides (R3PO) as materials for defect passivation, where photovoltaic performance was investigated depending on the substituents R. Electron‐donating ability of the substituents in R3PO was found to play an important role in passivation. Cyclohexyl substituent was better in achieving photovoltaic performance than linear hexyl substituent. The heterocyclic morpholine substituent bearing oxygen and nitrogen in cyclohexyl form further improved photovoltaic performance due to its enhanced electron‐donating ability. Compared with an untreated PSC, the trimorpholinophosphine oxide (TMPPO)‐treated PSC improved the power conversion efficiency from 21.95% to 23.72%. Additionally, the dark‐storage stability test with an unencapsulated device showed that the TMPPO‐treated device maintained 92.7% of its initial PCE after 1250 h, while 86.8% was maintained for the untreated device. Three hundred hour‐light‐soaking of the encapsulated devices revealed that the operational stability of the TMPPO‐treated PSC was superior to the untreated device.image

Cover Image, Volume 62, Issue 8

A novel three‐component covalent organic polymer (COP) named SLEL‐6 was prepared based on Schiff base chemistry through a multi‐component method for ciprofloxacin removal from an aqueous solution. It could be embedded in sodium alginate (SA) to obtain spherical COP/SA composite beads (SLEL‐6/SA beads) with enhanced adsorption ability and boosted recyclability. Details are found in the article from Yangxue Li and colleagues. DOI: 10.1002/pol.20230258 image

Metallosalen modified carbon nitride a versatile and reusable catalyst for environmentally friendly aldehyde oxidation

The development of environmentally friendly catalysts for organic transformations is of great importance in the field of green chemistry. Aldehyde oxidation reactions play a crucial role in various industrial processes, including the synthesis of pharmaceuticals, agrochemicals, and fine chemicals. This paper presents the synthesis and evaluation of a new metallosalen carbon nitride catalyst named Co(salen)@g-C3N4. The catalyst was prepared by doping salicylaldehyde onto carbon nitride, and subsequently, incorporating cobalt through Schiff base chemistry. The Co(salen)@g-C3N4 catalyst was characterized using various spectroscopic techniques including Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Infrared Spectroscopy (IR), and Thermogravimetric Analysis (TGA). Furthermore, after modification with salicylaldehyde, the carbon nitride component of the catalyst exhibited remarkable yields (74–98%) in oxidizing various aldehyde derivatives (20 examples) to benzoic acid. This oxidation reaction was carried out under mild conditions and resulted in short reaction times (120–300 min). Importantly, the catalyst demonstrated recyclability, as it could be reused for five consecutive runs without any loss of activity. The reusable nature of the catalyst, coupled with its excellent yields in oxidation reactions, makes it a promising and sustainable option for future applications.

Energy landscapes of homopolymeric RNAs revealed by deep unsupervised learning

Conformational dynamics of RNA plays important roles in a variety of cellular functions such as transcriptional regulation, catalysis, scaffolding, and sensing. Recently, RNAs with low-complexity sequences have been shown to phase separate and form condensate phases similar to lowcomplexity protein domains. The affinity for phase separation and the material characteristics of RNA condensates are strongly dependent on sequence composition and patterning. We hypothesize that differences in the affinities for RNA phase separation can be uncovered by studying sequence-dependent conformational dynamics of single RNA chains. To this end, we have employed atomistic simulations and deep dimensionality reduction techniques to map temperature-dependent conformational free energy landscapes for 20 base-long homopolymeric RNA sequences: poly(U), poly(G), poly(C), and poly(A). The energy landscapes of homopolymeric RNAs reveal a plethora of metastable states with qualitatively different populations stemming from differences in base chemistry. Through detailed analysis of base, phosphate, and sugar interactions, we show that experimentally observed temperature-driven shifts in metastable state populations align with experiments on RNA phase transitions. Specifically, we find that the thermodynamics of unfolding of homopolymeric RNA follows the poly(G) > poly(A) > poly(C) > poly(U) order of stability, mirroring the propensity of RNA to form condensates. To conclude, this work shows that at least for homopolymeric RNA sequences the single-chain conformational dynamics contains sufficient information for predicting and quantifying condensate forming affinities of RNAs. Thus, we anticipate that atomically detailed studies of temeprature -dependent energy landscapes of RNAs will be a useful guide for understanding the propensity of various RNA molecules to form condensates.

Mitochondrial transcription factor A (TFAM) has 5′-deoxyribose phosphate lyase activity in vitro

Mitochondrial DNA (mtDNA) plays a key role in mitochondrial and cellular functions. mtDNA is maintained by active DNA turnover and base excision repair (BER). In BER, one of the toxic repair intermediates is 5′-deoxyribose phosphate (5′dRp). Human mitochondrial DNA polymerase γ has weak dRp lyase activities, and another known dRp lyase in the nucleus, human DNA polymerase β, can also localize to mitochondria in certain cell and tissue types. Nonetheless, whether additional proteins have the ability to remove 5'dRp in mitochondria remains unknown. Our prior work on the AP lyase activity of mitochondrial transcription factor A (TFAM) has prompted us to examine its ability to remove 5′dRp residues in vitro. TFAM is the primary DNA-packaging factor in human mitochondria and interacts with mitochondrial DNA extensively. Our data demonstrate that TFAM has the dRp lyase activity with different DNA substrates. Under single-turnover conditions, TFAM removes 5′dRp residues at a rate comparable to that of DNA polymerase (pol) β, albeit slower than that of pol λ. Among the three proteins examined, pol λ shows the highest single-turnover rates in dRp lyase reactions. The catalytic effect of TFAM is facilitated by lysine residues of TFAM via Schiff base chemistry, as evidenced by the observation of dRp-lysine adducts in mass spectrometry experiments. The catalytic effect of TFAM observed here is analogous to the AP lyase activity of TFAM reported previously. Together, these results suggest a potential role of TFAM in preventing the accumulation of toxic DNA repair intermediates.

Acid–base chemistry and the economic implication of electrocatalytic carboxylate production in alkaline electrolytes

Acid–base chemistry and the economic implication of electrocatalytic carboxylate production in alkaline electrolytes

Thermoresponsive Injectable Hydrogel To Mimic the Heat- and Strain-Stiffening Behavior of Biopolymers toward Muscle Cell Proliferation.

Injectable hydrogels with nonlinear mechanical attributes to emulate natural biopolymers hold paramount significance in tissue engineering, offering the potential to create scaffolds that seamlessly mimic the biomechanical intricacies of living tissues. Herein, we unveil a synthetic design strategy employing Schiff base chemistry to furnish a peptide-polymer hierarchical contractile injectable hydrogel network. This innovative design demonstrates cross-linking of supramolecular peptide nanostructures such as nanofibers, 1NF, and twisted bundles, 1TB, with a thermosensitive aldehyde-functionalized polymer, PCHO. These networks exhibit interesting nonlinear mechanical stiffening responses to temperature and external stress. Furthermore, the hydrogels transform into a gel state at physiological temperature to exhibit injectable behavior and demonstrate compression load-bearing capabilities. Finally, the hydrogel network exhibits excellent biocompatibility and cell proliferation toward fibroblast, L929, and myoblast, C2C12, to validate their use as potential extracellular matrix mimetic injectable scaffolds.

Comparative Evaluation to Surface Roughness of Modified Heat Cured Acrylic Resin by Zinc Oxide Nanoparticles and CAD/CAM Denture Base Materials - In Vitro Study

One of the most promising CAD/CAM approaches is milling denture base materials from highly condensed pre-polymerized resin discs. In an effort to overcome the disadvantages of acrylic resin denture base materials, nano-filler materials have been added as well as denture base chemistry adjusted to strengthen the denture base.This eliminates disadvantages associated with polymerization shrinkage compared to conventional heat-cured acrylic resin. Aim of this study: evaluate the surface roughness of PMMA acrylic resin after strengthening the denture- base by addition of zinc oxide nano-filler material to acrylic resin PMMA with concentration (1%) and compare with milled CAD/CAM and non-modified heat-cured PMMA denture base materials. Materials and methods: thirty specimens of acrylic resin PMMA were prepared and divided into three groups 10 specimens for each groups as follows; Control Group (Group1) without ZnO nanoparticles ; Group (2) with (1%) by weight of ZnO nanoparticles ; Group (3) milled CAD/CAM.Each specimen is of dimension ( 10 x 10 x 3 ) in mm and was fabricated using conventional processing method and milling the CAD/CAM blocks .Results: showed the lowest mean value was recorded by milled CAD/CAM (0.230 Ra) Then the non-significant reduction with mean value (0.312 Ra) by PMMA+ ZnO 1% and highest mean value of surface roughness was recorded by pure PMMA without additive (0.327 Ra).Conclusions: There were significant differences between control group PMMA and milled (CAD/CAM) with slight reduction of surface roughness of PMMA with (1%) Zno nanoparticles.

NO measurements in high temperature hydrogen flames: The crucial role of the hydrogen oxidation chemistry for accurate NO predictions

The current work investigates the formation of Nitric Oxide (NO) in hydrogen–air flames, over a wide range of flame temperatures. The use of hydrogen allows improved focus on the thermal-NO pathway by removing the complexity introduced by the prompt-NO pathway, which has been shown to be an important contributor to inaccurate predictions of absolute post-flame NO concentrations in hydrocarbon flames. This experimental study is conducted at atmospheric pressure using stoichiometric, premixed, laminar stagnation flames. Adiabatic flame temperatures ranging from 1600K to 2300K are achieved by varying the argon concentration in air. One-dimensional velocity, temperature, and NO concentration profiles are measured using non-intrusive laser diagnostics: Particle Tracking Velocimetry (PTV), NO multiline thermometry, and NO Laser Induced Fluorescence (NO-LIF), respectively. Results show that the experimental velocity profiles are incorrectly captured by the studied mechanisms, especially at low and high temperatures. This suggests that major inaccuracies are present in the hydrogen oxidation chemistry of the thermochemical models, regardless of their optimisation methodology. Furthermore, NO-LIF profiles show major discrepancies between all the studied mechanisms and the experiments, especially at elevated temperatures. The disagreement stems from an inaccurate description of the base chemistry of the models. These inaccuracies arise specifically from the description of the radical pool driving the flame behaviour and NO formation. This study demonstrates the need for model optimisation on experimental measurements using pure hydrogen 1D flames to obtain an accurate description of the hydrogen oxidation chemistry at play. This would lead to an improved description of the NOx sub-chemistry of any hydrogen, or hydrocarbon, combustion system.

Effect of Brain-Based Learning on Conceptual Change in Acid, Base and Salt among Chemistry Students of Varied Cognitive Ability in Onitsha Education Zone

The study investigated the effect of brain-based learning on conceptual change in acid, base and salt among chemistry students of varied cognitive ability in Onitsha Education Zone. Three research questions guided the study and five hypotheses were tested at 0.05 alpha level. Quasi-experimental design was used in the study, specifically, the pretest-posttest non-equivalent control group design. The study population comprised 3, 103 SS2 students offering chemistry in Onitsha Education Zone, out which 108 students were selected using random and purposive sampling techniques. The instruments used for data collection were Test of Logical Thinking (TOLT) adopted from Tobin and Capie (1981) and Chemistry Students’ Conceptual Change Test (CSCCT) adopted from Zudonu (2013). Data was generated for the study by administering the instruments as pretest and posttest. Research questions were answered using mean and standard deviation while analysis of covariance was used to test the null hypotheses. The findings of the study showed that students taught acid, base and salt chemistry using brain-based learning had significantly higher mean conceptual change scores than those taught using lecture method. Also, there was a significant influence of cognitive ability level and gender on students’ conceptual change. It was recommended that seminars and workshop should be organized for chemistry teachers by school administrators to acquaint them with the effective ways of integrating brain-based learning into the teaching process of chemistry.

SynAsk: unleashing the power of large language models in organic synthesis.

The field of natural language processing (NLP) has witnessed a transformative shift with the emergence of large language models (LLMs), revolutionizing various language tasks and applications, and the integration of LLMs into specialized domains enhances their capabilities for domain-specific applications. Notably, NLP has made significant strides in organic chemistry, particularly in predicting synthetic tasks, paving the way for the development of LLMs tailored to the organic chemistry field. In this work, we introduce SynAsk, a comprehensive organic chemistry domain-specific LLM platform developed by AIChemEco Inc. By fine-tuning an LLM with domain-specific data and integrating it with a chain of thought approach, SynAsk seamlessly accesses our knowledge base and advanced chemistry tools in a question-and-answer format. This includes functionalities such as a basic chemistry knowledge base, molecular information retrieval, reaction performance prediction, retrosynthesis prediction, chemical literature acquisition, and more. This novel methodology synergizes fine-tuning techniques with external resource integration, resulting in an organic chemistry-specific model poised to facilitate research and discovery in the field. Accessible at https://synask.aichemeco.com, SynAsk represents a significant advancement in leveraging NLP for synthetic applications.

Using a combination technique for the assessment of students’ cognitive structures on acid–base chemistry

This study aims to determine the cognitive structures of students at different educational levels (8th grade and 12th grade) related to acid–base chemistry. The research was designed as a case study and structured in two stages. The first stage analyzed concepts related to acid–base chemistry and their direction and strength in students’ knowledge structures. The second stage determined the descriptive and structural features of students’ knowledge structures related to acid–base chemistry in a more holistic approach. The study was carried out with a total of 160 students, 80 grade 8th and 80 12th grade students. A word association test (WAT) and the free writing technique (FWT) were used together. In the WAT, ten different frequency ranges were determined forming cognitive structure maps of the students. With high-frequency values on the map, it was found that the number of stimulus and response words decreased but the strength of associations increased. In frequency ranges where the frequency values of associations were low, it was found that the number of stimulus and response words increased and the cognitive structure organization was at the most advanced level compared to other frequency ranges, but the strength of associations was weak. In general, it was observed that there were no bidirectional and cross-associations between the concepts in the cognitive structures of the students about chemistry and that there was a static structure that included one-way associations only. Additionally, the concepts in the cognitive structures of students related to acid–base chemistry were analyzed in terms of their structural characteristics. It was found that, in the cognitive structures of the students there were no associations between many concepts that should be related to each other.