Small-molecule Organic Compounds Research Articles

Insights into flotation separation mechanism of chalcopyrite from galena using mercaptosuccinic acid as a novel depressant: Experimental and MDS studies

The separation of polymetallic sulfide ores by flotation is a difficult task in the mineral processing industry. In this investigation, a small-molecule organic compound, mercaptosuccinic acid (MSA), was used as a new depressant for inhibiting galena in chalcopyrite flotation. Micro-flotation and surface wettability tests indicated that MSA pronouncedly weakened the floatability of galena but not chalcopyrite, resulting in marked differences in their flotation recovery. Findings of Fourier transform infra-red (FT-IR) spectroscopy measurements and reagent adsorption trials showed that MSA was strongly adsorbed on galena, resulting in the inability of the collector to effectively interact with galena. Atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) analyses further corroborated that MSA showed a greater affinity for galena than chalcopyrite, this behavior markedly altered the superficial chemical environment of galena. Molecular dynamic simulations (MDS) showed that MSA increased the concentrations of H2O molecules on galena, which enhanced the surface hydrophilicity of galena.

Efficient activation of peroxymonosulfate by Mn single-atom: Critical role of Mn-N4 coordination for generating singlet oxygen

Single-atom catalysts with high catalytic efficiency and simple preparation methods are critical for activation of peroxymonosulfate (PMS) to degrade emerging contaminants in aqueous solution. Herein, manganese single-atom nitrogen-doped carbon catalyst (SA-Mn-NC) was synthesized by precisely controlled catalytic carbonization using small-molecule organic compounds as precursors, and Mn was uniformly dispersed in a single-atom state and existed in the ligand structure of Mn-N4. Thus, the SA-Mn-NC had considerable catalytic activity and can realize 100% bisphenol A degradation within 3 min with kobs of 1.56 min−1, which was 4.7 and 9.2 times higher than that of NC (0.33 min−1) and Mn-NC (0.17 min−1). Moreover, SA-Mn-NC has excellent environmental adaptability, negligible metal leaching concentration, good cycling stability, and selectivity to electron-rich compounds. EPR tests, quenching experiments, electrochemical measurements, and selective degradation results together confirmed that singlet oxygen (1O2) was the main active species in the SA-Mn-NC/PMS system. The coupled N-active sites of Mn-N4 contribute to the efficient activation of PMS to generate 1O2 and achieve high catalytic turnover frequency. This work provides a simple strategy for the preparation of single-atom catalysts with considerable PMS catalytic efficiency and negligible metal leaching toxicity, which is of guiding importance for the design of single-atom catalysts for high-efficiency water treatment.

Small-Molecule Organic Cathodes with Carbon Coating for Highly Efficient Potassium-ion Batteries.

Small-molecule organic cathodes face dissolution in potassium-ion batteries (PIBs). For the first time, an interesting and effective strategy is unveiled to resolve this issue by designing a new soluble small-molecule organic compound namely [N,N'-bis(2-anthraquinone)]-1,4,5,8-naphthalenetetracarboxdiimide (NTCDI-DAQ, 237 mAh g-1 ): Through the precise manipulation of carbonization temperature and time, the molecules on the surface of NTCDI-DAQ particles can be transformed into amorphous carbon with controllable thickness. This strategy called surface self-carbonization can form a carbon protective layer on organic cathodes and significantly increase their insolubility against liquid electrolytes without affecting the electrochemical behavior of bulk particles. As a result, the as-obtained NTCDI-DAQ@C sample displays significantly improved cathode performance in PIBs. In half cells, NTCDI-DAQ@C shows superior capacity stability of 84 % compared to 35 % of NTCDI-DAQ during 30 cycles under the same conditions. In full cells with a KC8 anode, NTCDI-DAQ@C delivers a peak discharge capacity of 236 mAh g-1 cathode and a high energy density of 255 Wh kg-1 cathode in 0.1-2.8 V, with 40 % capacity retention during 3000 cycles at 1 A g-1 . To the best of our knowledge, the integrated performance of NTCDI-DAQ@C is among the best of soluble organic cathodes reported in PIBs.

Synthesis of Nitrogen-Conjugated 2,4,6-Tris(pyrazinyl)-1,3,5-triazine Molecules and Electrochemical Lithium Storage Mechanism

Organic anode materials for lithium-ion battery have attracted widespread attention due to their diversity in organic linker functional species and the ability to tune their molecular levels. However, the rational design of advanced organic anodes with high reversible capacity and intentional organic molecular design requires a deep understanding of their mechanism for use in small-molecule organic rechargeable batteries. Herein, an optimized small-molecule-based organic anode material containing highly efficient active sites was developed for use in an organic lithium-ion battery. A small-molecule organic compound, 2,4,6-tris(pyrazinyl)-1,3,5-triazine (TPT), was formed by the trimerization of the 2-cyanopyrazine monomer. This molecule was rationally designed and evaluated as a lithium-ion battery organic anode material. TPT has a relatively small structure, but a superior reversible specific capacity was still achieved. Excitingly, TPT2 (liquid-phase synthetic) released a reversible capacity of 622 mAh g–1 at 100 mA g–1. Moreover, impressive long-term cycling performance was obtained, with a storage capacity of 541 mAh g–1 at 800 mA g–1 after 500 cycles. This demonstrated the durable cyclic stability of TPT2, which also achieved excellent rate performance at different current densities from 100 mA g–1 to 1.6 A g–1. The lithium storage mechanism of TPT was studied by theoretical calculations and ex situ Fourier transform infrared spectroscopy (FTIR) combined with X-ray photoelectron spectroscopy (XPS) characterization, which demonstrated that multiple active sites consisting of −C–N and −C═N groups were responsible for its superior lithium storage performance. This study provides a new understanding of the energy storage mechanism in small-molecule organic-based anode electrodes.

Synthesis, Properties, and Application of Small-Molecule Hole-Transporting Materials Based on Acetylene-Linked Thiophene Core.

Three small molecule organic compounds based on conjugated acetylene-linked methoxy triphenylamine terminal groups with different substituted thiophene cores were synthesized and firstly applied as hole-transporting materials (HTMs). The electron-deficient acetylene linkers can tune the energy levels of frontier molecular orbitals. The physical property measurements show that the HTMs (CJ-05, CJ-06, and CJ-07) possess good stability, hydrophobicity, and film-forming ability. Further, the HTMs were applied in the MAPbI3-based perovskite solar cells (PSCs), and the best power conversion efficiency (PCE) of 6.04%, 6.77%, and 6.48% was achieved, respectively, which implies that they exhibit great potential in photovoltaic applications.

Effective Surface Modification of 2D MXene toward Thermal Energy Conversion and Management.

Thermal energy management is a crucial aspect of many research developments, such as hybrid and soft electronics, aerospace, and electric vehicles. The selection of materials is of critical importance in these applications to manage thermal energy effectively. From this perspective, MXene, a new type of 2D material, has attracted considerable attention in thermal energy management, including thermal conduction and conversion, owing to its unique electrical and thermal properties. However, tailored surface modification of 2D MXenes is required to meet the application requirements or overcome specific limitations. Herein, a comprehensive review of surface modification of 2D MXenes for thermal energy management is discussed. First, this work discusses the current progress in the surface modification of 2D MXenes, including termination with functional groups, small-molecule organic compound functionalization, and polymer modification and composites. Subsequently, an in situ analysis of surface-modified 2D MXenes is presented. This is followed by an overview of the recent progress in the thermal energy management of 2D MXenes and their composites, such as Joule heating, heat dissipation, thermoelectric energy conversion, and photothermal conversion. Finally, some challenges facing the application of 2D MXenes are discussed, and an outlook on surface-modified 2D MXenes is provided.

Category theory and organic electronics

Inorganic semiconductors and conducting polymers are described by band conduction models with delocalized electrons, whereas small-molecule organic compounds are described by hopping conduction between localized molecular orbitals. However, the latter devices can reproduce fully the characteristics of semiconductor devices. Why are they so different and yet so similar? We will try to answer this question using Category theory and considering the meaning of electrical transport in electronic materials. The meaning of the category theory in physics is to consider different mathematical entities under a common mathematical structure.In this paper, the basic idea of category theory is first explained in detail using the example of complex impedance, and then four examples of its application are discussed. The derivation of the Mott-Gurney equation and the negative capacitance in OLED are discussed as examples of solving problems by moving to different categories. After those simple examples of formal rewriting from physical entity to mathematical entity, it is shown that electrical connection and electrical contact lead to direct sums and direct products of conducting states, based on the duality concept. We conclude that small-molecule organic compounds are not a mere branch of semiconductors, but rather equal counterparts of semiconductors in duality that are necessary to clarify the origin of the difference and similarity between organic electronics and semiconductor physics. Finally, by considering the electrical responses of OLEDs and OFETs in the immittance category, we show that they can be described under a common operating dynamic and propose a new operating model for OFETs.

Composite elastomers with on-demand convertible phase separations achieve large and healable electro-actuation.

Phase separation has been widely exploited for fabricating structured functional materials. Generally, after being fabricated, the phase structure in a hybrid material system has been set at a specific length scale and remains unchanged during the lifespan of the material. Herein, we report a strategy to construct on-demand and reversible phase switches among homogenous, nano- and macro-phase separation states in a composite elastomer during its lifespan. We trigger the nanophase separation by super-saturating an elastomer matrix with a carefully selected small-molecule organic compound (SMOC). The nanoparticles of SMOC that precipitate out upon quenching will stretch the elastomer network, yet remain stably arrested in the elastomer matrix at low temperatures for a long time. However, at elevated temperatures, the nano-phase separation will transform into the macro-one. The elastic recovery will drive the SMOC onto the elastomer surface. The phase-separated structures can be reconfigured through the homogeneous solution state at a further elevated temperature. Taking advantage of the reversible phase switches leads to a novel strategy for designing high-performance dielectric elastomers. The in situ formed nanoparticles can boost the electro-actuation performance by eliminating electro-mechanical instability and lead to a very large actuation strain (∼146%). Once the actuator broke down, SMOC could on-demand be driven to the breakdown holes and heal the actuator.

Novel insight into iodine enrichment in alluvial-lacustrine aquifers: Evidence from stable carbon and iron isotopes

Reductive dissolution of Fe (oxyhydr)oxides triggered by biodegradation of organic matter (OM) are considered to be key processes controlling iodine (I) release in groundwater systems. However, the precise mechanisms involved in release from organic matter degradation and from Fe (oxyhydr)oxides are unclear. In this study, dual stable isotope analysis (δ13C and δ56Fe) was combined with ultraviolet–visible spectral characterization of dissolved organic matter to elucidate the mechanisms of iodine enrichment in groundwater of the central Yangtze River basin, China, which represents Quaternary alluvial-lacustrine floodplains. High iodine groundwater mainly occurs along the Yangtze River (YR) and Han River (HR), with a maximum concentration of 1220 μg/L. The results suggest that methanogenesis driven by the biodegradation of high molecular weight organic compounds can promote the reductive dissolution of amorphous Fe (oxyhydr)oxides, which is the predominant process controlling iodine enrichment in the YR groundwater system. In addition, fermentation accompanied by sulfate reduction can also trigger the release of iodine into groundwater. The reductive dissolution of crystallized Fe (oxyhydr)oxides driven by the fermentation of small-molecule organic compounds is the dominant process responsible for iodine enrichment in the HR groundwater system. This study provides novel insight into the mechanisms of iodine enrichment in Quaternary alluvial-lacustrine aquifers.

Impact of charge character on anionic cyanine-based organic salt photovoltaics

Small bandgap organic compounds with absorption in the near-infrared are exciting materials for a variety of applications ranging from light harvesters in photovoltaics to active agents in photodynamic therapy. Organic salts, a class of small molecule organic compounds comprised of an ionic chromophore and a counterion, have been used in opaque and transparent photovoltaics, primarily as donor materials in bilayer architectures. They possess excellent molecular extinction coefficients with near-infrared selective absorption, adjustable bandgaps, and tunable energy levels. To approach organic salt photovoltaics from a new perspective, we fabricated devices with an unexplored group of anionic salts comprised of a near-infrared absorbing chromophore paired with a varying number of cationic counterions. We observed different donor and acceptor decay trends in external quantum efficiencies that allowed us to separate and independently quantify exciton diffusion and charge transfer for each salt. Increased charge character on the chromophore greatly improves hole transport, as anions with a net −3 charge have charge collection lengths greater than four times those of corresponding singly charged chromophores. This presents an interesting platform for independent quantification of exciton diffusion and charge transport of an active material in a single photovoltaic device and demonstration of the important role of charge on the chromophore. The dependence of charge transport capabilities on charge character of the chromophore will be a useful tool in the design of future organic salts to engineer materials for higher efficiency transparent photovoltaics.

A universal small-molecule organic cathode for high-performance Li/Na/K-ion batteries

Organic solids are mainly composed by organic molecules interacted by Van der Waals forces, which indicates that every organic molecule can independently store electrons and counter metal ions during redox reaction in rechargeable metal-ion batteries. However, the serious dissolution problem as well as the solvent structure in electrolytes limits this universal capability for organic electrodes. In this article, a novel small-molecule organic compound namely 1,1′-(1,4-phenylene)-bis(perylene-3,4,9,10-tetracarboxylic dianhydride) (2PTCDA, 125 mAh g−1) is intentionally designed, in order to increase the insolubility against liquid electrolytes and partially extend its π-π aromatic skeleton without sacrificing the redox activity and specific capacity. Based on the insolubility and the properly-selected electrolytes, 2PTCDA can exhibit almost the same cathode performance in all Li/Na/K-ion half and full cells. Specifically, 2PTCDA can deliver the redox potential range of 1.4–3.6 V (vs. Li/Na/K) and discharge capacities of 120–137 mAh g−1 in Li/Na/K-ion half cells.

Characterization of biochar-derived organic matter extracted with solvents of differing polarity via ultrahigh-resolution mass spectrometry

In recent years, biochar, a porous carbon-based material, has gained attention for its application prospects in contaminated soil remediation and soil improvement. Biochar-derived organic matter has a key role in influencing the migration and transformation of soil elements and pollutants. However, existing research concerning the molecular characteristics of biochar-derived organic matter is limited. Here, we used four polar solvents — dichloromethane (CH2Cl2), acetone (CH3COCH3), methanol (CH3OH), and distilled water (H2O) — to extract organic matter from soybean straw biochar and wheat straw biochar by accelerated solvent extraction (ASE). We characterized the extracts using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). We found considerable differences in organic matter according to the extraction solvents; such differences were related to the polarity of the solvent, as well as intermolecular forces between the solvent and organic matter. CH3OH extracted the most biochar-extractable organic matter components because CH3OH can weaken or destroy oxygen bridge bonds in biochar and form hydrogen bonds with small-molecule organic compounds. CH3OH and H2O have strong extraction capacity for compounds containing heteroatoms. CH2Cl2-extractable organic matter is relatively labile and bioavailable, while CH3OH- and H2O-extractable organic matters are relatively stable. In addition, the binding capacity of biochar-derived organic matter for minerals and pollutants differed among fractions, in part because of differences in molecular weight, atomic O/C and H/C ratios, heteroatom distribution, and biomolecular compounds present in biochar-derived organic matter. The findings in this study help to select appropriate extractants to analyze biochar-derived organic matter for various research purposes, and provides a theoretical basis for biochar-based remediation of contaminated soil.

Small molecular benzoquinone derivative 1,3,5-tri(4-benzoquinone phenyl) benzene based on 6-electron reaction used as cathode material for Li-ion batteries

Benzoquinone derivatives have attracted much attention as organic cathode materials for lithium ion batteries due to their high theoretical specific capacity. To address the deficiencies of benzoquinone derivatives, a small molecule organic compound 1,3,5-tri(4-benzoquinone phenyl) benzene (TBPB) based on the benzoquinone active unit is designed and synthesized. The cycling stability and rate performance of TBPB electrode are further improved by using three-dimensional porous carbon paper (CP) as the current collector. The TBPB cathode with the CP collector maintains a discharge capacity of 193 mAh g−1 after 200 cycles at 0.1C, and the capacity retention rate is 93.3%.

Possibilities and challenges of small molecule organic compounds for the treatment of repeat diseases.

The instability of repeat sequences in the human genome results in the onset of many neurological diseases if the repeats expand above a certain threshold. The transcripts containing long repeats sequester RNA binding proteins. The mechanism of repeat instability involves metastable slip-out hairpin DNA structures. Synthetic organic chemists have focused on the development of small organic molecules targeting repeat DNA and RNA sequences to treat neurological diseases with repeat-binding molecules. Our laboratory has studied a series of small molecules binding to mismatched base pairs and found molecules capable of binding CAG repeat DNA, which causes Huntington’s disease upon expansion, CUG repeat RNA, a typical toxic RNA causing myotonic dystrophy type 1, and UGGAA repeat RNA causing spinocerebellar ataxia type 31. These molecules exhibited significant beneficial effects on disease models in vivo, suggesting the possibilities for small molecules as drugs for treating these neurological diseases.

A small molecule organic compound applied as an advanced anode material for lithium-ion batteries.

We choose copper(II) ions to salinize maleic acid, then form a layered copper maleate hydrate and apply this as an anode material for LIBs for the first time. The as-prepared material exhibits admirable electrochemical performance (404.6 mA h g-1 at 0.2 A g-1). A new hypothesis is developed for a better understanding of the unusual in situ XRD results and reaction mechanism.

Organic Thin Films Deposited by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) for Photovoltaic Cell Applications: A Review

Human society’s demand for energy has increased faster in the last few decades due to the world’s population growth and economy development. Solar power can be a part of a sustainable solution to this world’s energy need, taking into account that the cost of the renewable energy recently dropped owed to the remarkable progress achieved in the solar panels field. Thus, this inexhaustible source of energy can produce cheap and clean energy with a beneficial impact on the climate change. The considerable potential of the organic photovoltaic (OPV) cells was recently emphasized, with efficiencies exceeding 18% being achieved for OPV devices with various architectures. The challenges regarding the improvement in the OPV performance consist of the selection of the adequate raw organic compounds and manufacturing techniques, both strongly influencing the electrical parameters of the fabricated OPV devices. At the laboratory level, the solution-based techniques are used in the preparation of the active films based on polymers, while the vacuum evaporation is usually involved in the deposition of small molecule organic compounds. The major breakthrough in the OPV field was the implementation of the bulk heterojunction concept but the deposition of mixed films from the same solvent is not always possible. Therefore, this review provides a survey on the development attained in the deposition of organic layers based on small molecules compounds, oligomers and polymers using matrix-assisted pulsed laser evaporation (MAPLE)-based deposition techniques (MAPLE, RIR-MAPLE and emulsion-based RIR-MAPLE). An overview of the influence of various experimental parameters involved in these laser deposition methods on the properties of the fabricated layers is given in order to identify, in the forthcoming years, new strategies for enhancing the OPV cells performance.

Electrochemical and quantum mechanical investigation of various small molecule organic compounds as corrosion inhibitors in mild steel

The corrosion inhibition property of selected small organic compounds was investigated using electrochemical measurements, including potentiodynamic polarization (PDP), linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), and density functional theory (DFT) calculations. The inhibition efficiency (IE %) of the inhibitor on mild steel (MS) in 1 M HCl was then determined. Results show that the presence of the inhibitors resulted in decreased corrosion current density (Icorr) values and increased polarization resistance (Rp). Furthermore, the use of higher concentrations of inhibitors led to an increased inhibition efficiency. Tafel slopes and shifts in the Ecorr values suggested that the inhibitors tested are mixed-type inhibitors that form a protective layer on the surface of the substrate. Of the organic compound inhibitors tested, the inhibitor 4-ethylpyridine (EP) exhibited the highest Rp values and inhibition efficiency values from the PDP, LPR, and EIS analyses, respectively. DFT calculations showed negative adsorption energies and confirmed the chemisorption of the inhibitors allowing for the formation of a hydrophobic protective film against corrosion and correlations between the quantum chemical values and electrochemical data were demonstrated. The results show the influence of the presence of electronegative O, S, and N atoms, as well as the role of aromatic rings in the promotion of surface protection by preventing aggressive ionic species from binding onto MS.

Catalytic Efficiency of Carbon-Cementitious Microfiltration Membrane on the Ozonation-Based Oxidation of Small Molecule Organic Compounds and Its Alkaline Buffering Effect in Aqueous Solution.

In this study, powdered activated carbon (PAC) was added to replace the silica in a cementitious microfiltration membrane (CM) to solve the problems of the low mechanical strength and short lifetime of CMs. The carbon-cementitious microfiltration membrane (CCM) was fabricated by the dry pressing method and cured at room temperature. The bending strength of CCM was 12.69 MPa, which was about three times more than that of CM. The average pore size was 0.129 μm, and was reduced by about 80% compared to that of CM. The addition of PAC did not reduce the degradation efficiency of membrane catalytic ozonation. Because of the strong alkaline buffering ability of CCM, the CCM–ozone coupling process could eliminate the effect of the pH value of the solution. The strong alkaline environment inside the membrane pores effectively accelerated the ozone decomposition and produced oxidizing radicals, which accelerated the reaction rate and improved the utilization rate of ozone. The CCM–catalytic ozonation reaction of organic compounds occurred within the pores and membrane surface, resulting in the pH of the solution belonging to the neutral range. The addition of PAC accelerated the mass transfer and made the pollutants and oxidant react in the membrane pores and on the membrane surface. The reuse experiments of the CCM–ozone coupling process for removing nitrobenzene demonstrated that CCM has good catalytic activity and reuse stability. It broadens the application scope of CCM in the field of drinking water and provides theoretical support for the practical application of CCM.

Selenomethionine: A Pink Trojan Redox Horse with Implications in Aging and Various Age-Related Diseases.

Selenium is an essential trace element. Although this chalcogen forms a wide variety of compounds, there are surprisingly few small-molecule organic selenium compounds (OSeCs) in biology. Besides its more prominent relative selenocysteine (SeCys), the amino acid selenomethionine (SeMet) is one example. SeMet is synthesized in plants and some fungi and, via nutrition, finds its way into mammalian cells. In contrast to its sulfur analog methionine (Met), SeMet is extraordinarily redox active under physiological conditions and via its catalytic selenide (RSeR’)/selenoxide (RSe(O)R’) couple provides protection against reactive oxygen species (ROS) and other possibly harmful oxidants. In contrast to SeCys, which is incorporated via an eloquent ribosomal mechanism, SeMet can enter such biomolecules by simply replacing proteinogenic Met. Interestingly, eukaryotes, such as yeast and mammals, also metabolize SeMet to a small family of reactive selenium species (RSeS). Together, SeMet, proteins containing SeMet and metabolites of SeMet form a powerful triad of redox-active metabolites with a plethora of biological implications. In any case, SeMet and its family of natural RSeS provide plenty of opportunities for studies in the fields of nutrition, aging, health and redox biology.

Comparison of nitrogen removal efficiency and microbial characteristics of modified two-stage A/O, A2/O and SBR processes.

The low temperature of sewage in north China results in low performance of biological treatment at municipal wastewater treatment plants (MWTPs), especially in biological nitrogen removal. A modified two-stage A/O process with an embedded biofilm was proposed to enhance nitrogen removal. The operation performance of a pilot test was compared with an A2/O and SBR process at existing MWTPs to investigate the resistance to low temperature. The microbial communities for the three processes were compared based on the metagenomics results of 16sDNA high-throughput sequencing from activated sludge. The modified A/O resulted in a higher average removal of COD (90.12%) than A2/O (85.23%) and SBR (83.03%), especially of small-molecule organic compounds (< 500Da) and macromolecular refractory organics (> 5kDa); the TN removal rate of A2/O, SBR and the modified A/O was also increased from 74.47%, 70.63% and 78.46%, respectively. High-throughput sequencing revealed increased microbial diversity and an abundance of denitrifying functional bacteria was observed in the modified A/O process at low temperatures. The abundance of nitrite oxidation bacteria (NOB) including Nitrosomonas and Nitrospira, the amount was 1.76% and 2.34% in modified A/O, respectively, whereas NOB only accounted for 1.82% in A2/O and 1.35% in SBR.