NH Bond Research Articles

Synthesis and application of dithiocarbamate oxadiazole thione for flotation separation of malachite from quartz and calcite

In this paper, 5-methyl hexyldithiocarbamate-1,3,4-oxadiazole-2-thione (MHCODT) was synthesized for the first time and introduced as a flotation collector in malachite flotation separation process from quartz and calcite. During the micro-flotation experiment, it was found that MHCODT showed stronger flotation ability and selectivity for malachite than conventional collector octyl hydroxamic acid (OHA), and achieved effective separation and enrichment of malachite. Measurements of contact angles, ζ-potentials and UV spectra demonstrated that MHCODT specifically adhered to the surface of malachite rather than quartz and calcite. Then, FTIR and X-ray photoelectron spectroscopy (XPS) demonstrated that Cu of malachite surface combined with S and N of MHCODT to form MHCODT-Cu(I) complexes, accompanied by the reduction of divalent Cu. The result of density functional theory (DFT) method indicated that the CS bonds and NH bonds in oxadiazole thione and the dithiocarbamate groups were the chemical reaction center. Based on the above test results, the adsorption models of MHCODT-Cu+ and MHCODT-Cu2+ were proposed.

Naphthalimide Molecular‐Doped Zinc Oxide Cathode Interfacial Layer Inhibits Charge Trapping in Organic Solar Cells

So far, the recombination center of photogenerated carriers caused by surface defects in ZnO results in poor thickness tolerance and inefficient charge extraction, severely limiting the performance and stability of inverted organic solar cells (OSCs). Therefore, hybrid cathode interfacial layers (CILs) are fabricated in devices by doping naphthalimide‐based molecules (NE and NDA) into ZnO, and significantly improved performance and stability are achieved for all tested devices. It is found that doping NE or NDA not only solves the problems of ZnO aggregation and surface defects, but also enhances the ability of charge transfer and lowers the work function of cathode. As a result, the OSCs based on PM6:Y6 with ZnO:NE 1% as a CIL exhibit the highest power conversion efficiency (16.72%), which is better than that of pristine ZnO. The research shows that N atoms in naphthalimide react with Zn ions, and −NH bonds form noncovalent interaction with heteroatoms in the blend, which is conducive to the formation of better chemical bond in hybrid materials and providing more transfer channels for carriers. This study highlights a promising strategy for enhancing the performance of inverted OSCs by the hybrid CIL strategy.

Thiocarbonyl fluoride generated in situ from difluorocarbene for cyclization of vicinal X-H substituted amines (X = N, O or S)

Difluorocarbene has served as a versatile intermediate in organic synthesis. The transformation of difluorocarbene into thiocarbonyl fluoride, which was discovered by us previously, can be developed as a synthetic tool for the cyclization of vicinal X-H substituted amines to provide various five-membered heterocycles. However, aryl amines are required to be used and difluoromethylation of the NH bond or a newly generated S-H bond cannot be suppressed. Herein we describe the use of thiocarbonyl fluoride generated in situ as a thiocarbonyl source for the cyclization of vicinal X-H substituted alkyl amines (X = N, O, S) to provide imidazolidine-2-thiones, oxazolidine-2-thiones and thiazolidine-2-thiones. The use of alkyl amines constructs different heterocycles with those obtained from aryl amines. The free NH bond remains intact without being difluoromethylated.

Enhancing circulating tumor cell capture: Amin-functionalized bilayer graphene biosensing with integrated chip-level system for point-of-care testing

Current research on the detection of circulating tumor cells (CTCs) as a diagnostic strategy is still in its early stages. Consequently, there is a need for an efficient platform to capture and accurately detect CTCs with high sensitivity. This study presents the development of a bio-sensing platform that employs a planar-gated graphene field-effect transistor (GFET). This platform is designed for the detection of CTCs associated with nasopharyngeal carcinoma (NPC). In this approach, bilayer graphene is functionalized through a low-damage nitrogen plasma treatment, and then further modified with specific antibodies to enable a label-free detection of CTCs. The real-time electrical signal changes of the sensor were analyzed, demonstrating advantages in terms of rapid sensing and cost-effective on chip fabrication and instrument investment. The results showed that the low-damage nitrogen plasma effectively aminated the graphene surface, with the C–NH2 bonds accounting for approximately 62.8 % of the nitrogen content. The linear detection range of the sensor from 1 cell/15 μl to 1 cell/1000 μl, with a limit of detection (LoD) of 1 cell/15 μl(∼66/ml). The sensitivity of the sensor was determined to be 0.040 V/decade with a linear regression of 0.93 and with high sensing specificity in mixture cells environments. The CTCs capture density on aminated graphene was calculated to be 238.6 ± 29.8 cells/mm2. We also integrated this sensor chip into a portable system, including the sensing and signal processing unit enabling fast detection and close to point-of-care diagnostic tests. This study provides a promising platform for the rapid and accurate detection of nasopharyngeal carcinoma CTCs for early detection and post-treatment monitoring.

Utilization of methyclothiazide adsorbed with malonamide for quantum chemical applications: A DFT and DFT-D2/D3 studies

Herein, cost-effective and reliable predictions were made for the optical and electronic properties of the combination of methyclothiazide and melonamide. Interactions between both the title molecules were computationally investigated. The combined structure of both molecules shows the occurrence of immense intramolecular charge transfer from melonamide toward methyclothiazide. Reduction in the band gap of the complex shows the stability of the complex. The combination of methyclothiazide and melonamide gave a red shift in the absorption wavelength to 250 nm. The higher Fourier transform infrared modes corresponding to the -NH bonds of methyclothiazide suggest these groups are suitable adsorption sites for the physisorption of melonamide. The values of first-order hyperpolarizability of the complex were found to be increased to 413.11 au as compared to that of probe methyclothiazide (286.07 au) and melonamide (73.94 au). The observed escalation in the first-order hyperpolarizability shows the potential capability of the proposed combination to be used as strong nonlinear optical materials.

Synthesis and spectroscopic characterization of thioparacetamol: Evidence for solvent-dependent changes in conformational equilibrium

The search for analogs of compounds with proved pharmacological activity frequently starts by obtaining those that result from simple chemical substitutions, have structural and mechanical characteristics suitable for inclusion in a formulation and close similarity with related lead compounds. With this aim, the isosteric replacement of the carbonyl functional group of paracetamol to obtain solid thioparacetamol was achieved through microwave mediated thionation of parent compound in very good yield (85 %). A thorough characterization of the compound prepared was performed by GC/MS spectrometry, FTIR and NMR (1H, 13C, COSY, HSQC and HMBC) spectroscopies and quantum chemical calculations derived from density functional theory. From the experimental and theoretical spectra, it was evidenced that the structural, vibrational and conformational properties of this compound vary whether the sample is solved in a solvent or not. The anti form (anti of the CS and NH bonds) was the preferred conformational isomer in the solid phase, while a conformational equilibrium of anti and syn forms was found for samples solved in different solvents. As polarity of solvents increased, proportion of the anti isomer increased as well.

Regioselective benzylation of imidazo[1,5-a]pyridines and indoles via iodine catalyzed reaction using alcohols - An approach to crystal structure prediction, DFT studies and Hirshfeld surface analysis

Iodine catalysed, regioselective C-1 benzylation of imidazo[1,5-a] pyridines and C-3 benzylation of indoles with diphenylmethanol has been developed. This new protocol provides an efficient protocol in the synthesis of the benzylation methodology as it targets exclusively CH bonds, even in presence of reactive NH bonds and variety of benzyl substituted indoles and imidazo[1,5-a] pyridines are synthesized with broad range of functionalities leads to the elegant formation of new CC bond under metal free conditions. This report represents a mild protocol for the synthesis of tris(heteroaryl/aryl) methanes from solid bench stable diarylmethanols. The products formed are interesting for their potential biological applications. The crystal structure of the compound 3k was determined by single crystal X-ray diffraction studies. The compound crystallized in triclinic crystal system with P-1 space group. The molecular structure is stabilized by short intermolecular interactions and intramolecular CH⋯N hydrogen bond interactions. The crystal structure also exhibits intermolecular CH⋯π, CCl⋯π and π⋯π stacking interactions. The intermolecular interactions are quantified through Hirshfeld surface analysis using fingerprint plots. The surface properties were analysed using 3D Hirshfeld surfaces. Further, the density functional theory calculations were carried to calculate the electronic properties of the molecule. The HOMO-LUMO energy gap is found to be 4.0981 eV. Finally, the chemically active sites on the molecule are identified by analysing the molecular electrostatic potential map.

Structure characterization and antioxidant activity of abalone visceral peptides-selenium in vitro

Peptide-selenium chelate is widely regarded as one of the best selenium supplements for relieving selenium deficiency. In this study, abalone visceral peptides (AVP) was used to prepare a new type of peptides-selenium chelate to develop an organic selenium supplement with antioxidant activity. AVP prepared by alcalase exhibited the highest selenium-chelating ability. UV–visible spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy and other structural analysis showed that selenium was mainly bound to the functional groups of –NH, –OH, –CH, CC, CO, and CN bonds on AVP. The formation of AVP-selenium chelate enhanced thermal stability and generated a new crystal structure. The ABTS•+ and •OH scavenging activities of AVP-selenium chelate were increased after in vitro digestion than that of AVP. Conclusively, this study analyzed the chelating mechanism of AVP and selenium from a structural perspective, which would provide a theoretical basis for the development of new selenium supplements.

Reversible bacteria-killing and bacteria-releasing cotton fabric with anti-bacteria adhesion ability for potential sustainable protective clothing applications

Multifunctional antibacterial surfaces are playing an essential role in various areas. Smart antibacterial materials equipped with switchable “bacteria-killing” and “bacteria-releasing” abilities have been created by scientists. However, most of them are either biologically incompatible, or complex fabricating procedures, or cannot prevent themselves from being attached by bacteria. In this work, a double-layer smart antibacterial surface was created easily by simple surface initiate atom transfer radical polymerization: the upper layer PSBMA provides anti-bacteria adhesion capacity, the NCl bond can show bacteria-killing ability and the under layer PNIPAM can exhibit bacteria-releasing property. Remarkably, the NCl bond can interconvert with the NH bond easily, which allows switching between bacteria-killing and bacteria-releasing. As a result, the functional cotton fabrics can resist about 99.66 % of bacteria attaching, kill nearly 100 % of attached bacteria after 5 min contacting and release about 99.02 % of the formerly attached bacteria. Furthermore, the functional cotton fabric kept excellent anti-bacteria adhesion ability (about 99.27 %) and bacteria-releasing capacity (about 98.30 %) after 9 cycles of re-chlorination. In general, a reversible “bacteria-killing” and “bacteria-releasing” cotton fabric was fabricated with well anti-bacteria adhesion capacity in a simple way, and this smart multifunctional cotton fabric shows a great potential application in reusable protective clothing.

Isolation, identification, and synergistic mechanism of a novel antimicrobial peptide and phenolic compound from fermented walnut meal and their application in Rosa roxbughii Tratt spoilage fungus

This study aimed to identify an antimicrobial peptide and phenolic compound combination derived from fermented walnut meal against Penicillium. victoriae, a fungus responsible for Rosa. roxbughii Tratt spoilage, and ultimately investigate their synergistic mechanism. YVVPW and salicylic acid (SA) had the highest antifungal activity among identified 4 antimicrobial peptides, including FGGDSTHP, ALGGGY, YVVPW, and PLLRW, and 15 phenolic compounds, respectively. Molecular docking verified that YVVPW bound to regulatory subunit via hydrogen-bond, hydrophobic, and π-π conjugate interactions. YVVPW and SA exhibited synergistic effects with average minimal inhibitory concentration decreasing by 85.44 ± 8.04%. Fluorescence spectroscopy demonstrated quenching of intrinsic Trp and Tyr fluorescence by interaction. FTIR and molecular docking results revealed formation of 3 hydrogen bonds via OH, CO, NH, and CH bonds in YVVPW + SA, with π-π stacking occurring between the benzene ring and five-membered ring. These reinforce potential application of this combination as an effective fungistatic combination in fruit preservation.

A silicone with one quaternary ammonium salt and three N-halamine sites in the repeating unit for improved antibiotic ability on submicrospheres

A silicone containing one cationic quaternary ammonium salt (QAS) and three N-halamine sites in the repeating unit was developed on SiO2 submicron spheres for better antibacterial performance, larger bactericidal area and easier recyclability. Briefly, a precursor (NDAM) with high content of N-halamine was prepared by the amidation reaction. Then, a SiO2@NDA nanocomposite was synthesized. Chlorination of the three imide NH bonds in the repeat unit finalized the synthesis of the bactericidal silicone (SiO2@NDA-Cl). The synthetic steps and products were characterized and the effect of the contents of NDAM in copolymer on antibacterial activity were systematically assayed. The SiO2@NDA-Cl showed higher deactivation abilities against both E. coli and S. aureus compared with their counterparts that contained only one cationic center or one N-halamine. This study has theoretical and practical application value for the development of new antibacterial materials.

Synergistic effect of phenyl phosphoric acid derivatives and DOPO on multifunctional epoxy resin: Fire safety, mechanical properties, transparency and hydrophobicity

A novel reactive flame retardant named PPDA was synthesized by neutralizing phenyl phosphate (PPOA) with 4,4′-diamino diphenyl ether (ODA). When 2.5 wt% of PPDA was incorporated into epoxy resin (EP) alongside 2.5 wt% of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), EP/PPDA/DOPO composite possessed UL-94 V-0 rating and a limited oxygen index (LOI) of 34.2% while exhibiting a remarkable synergistic effect between PPDA and DOPO. In contrast to pure EP, EP/PPDA2.5/DOPO2.5 exhibited a significant reduction in peak heat release rate, total heat release, and total smoke production by 56.3%, 23.0%, and 26%, respectively, when increasing char yield to 30.2%. The synergistic system formed char with organic phosphorus structures containing P-O-C, P-N-C, and P=O bonds, along with benzene rings in the condensed phase, meanwhile forming P-containing radicals and non-flammable nitrogen-containing compounds in the gas stage. Additionally, it was discovered that the presence of the NH bond in PPDA and the P-H bond in DOPO facilitated the ring-opening reaction of the epoxy groups, which contributed to the preservation of the mechanical properties and transparency of the EP. PPDA/DOPO was a halogen-free, low-cost alternative for flame retardants, demonstrating excellent performance and potential for future applications.

Aggregation-induced emission enhancement N, S-CQDs for selective detection of CIP in the environment

Carbon quantum dots (CQDs) have been extensively researched as fluorescent probes, but there are few reports on fluorescence-enhanced probes. Herein, nitrogen and sulfur co-doped CQDs (N, S-CQDs) with blue aggregation-induced emission enhancement (AIEE) fluorescence were synthesized by a one-step hydrothermal reaction. N, S-CQDs can rely on the presence of –OH, C=O, –NH2, and ether bonds on their surfaces and the formation of hydrogen bonds by ciprofloxacin (CIP) containing Ar-F and –COOH functional groups to achieve effective charge transfer. In addition, CIP forces N, S-CQDs to aggregate to form cross-linked structures, which effectively limits the vibration and rotation of N, S-CQDs, leading to enhanced fluorescence of N, S-CQDs. Based on the above intermolecular charge transfer and AIEE between N, S-CQDs and CIP, an efficient and sensitive nano fluorescent probe for the detection of CIP in real water samples was developed, which can achieve sensitive detection of 3.33 × 10−8–1.13 × 10−6 M CIP.

Switchable bacteria-killing and bacteria-releasing surface fabricated from regenerable PNIPAM-based N-halamine cotton fabrics

So far, more and more multifunctional antibacterial materials qualified with “bacteria-killing” and “bacteria-releasing” capacities have been developed by researchers to kill live bacteria and release the killed bacteria. However, most of these surfaces are biologically incompatible and have a complex production process. In this work, we created a PNIPAM-based N-halamine cotton fabric via simple Si-ATRP (surface-initiated atom transfer radical polymerization) and chloridized in ordinary diluted sodium hypochlorite solutions. Notably, the NCl bond at N-halamine cotton fabrics and the NH bond at PNIPAM can interconvert with each other easily. The NCl bond provides the possibility of bacteria-killing. Simultaneously, the NH bond can change the surface wettability and cooperate with the stretch of PNIPAM chains at a lower temperature, providing the ability of bacteria-releasing. As a result, the PNIPAM-based N-halamine cotton fabrics have excellent antibacterial efficiency in the form of “N-Cl” and a remarkable bacteria-releasing efficiency in the form of “N-H”. In addition, the functional surface has good biocompatibility. Overall, we develop an easy way to create switchable “bacteria-killing” and “bacteria-releasing” cotton fabrics, and this smart surface shows a potential application in biomedical and hospital surfaces.

Novel functional TiPO/SiO2 catalyst enriched surface hydroxyl groups for highly selective catalytic oxidation of cyclohexylamine to cyclohexanone oxime

Developing a low-cost and environmentally benign alternative approach for the production of cyclohexanone oxime is strategic due to the increasing need for caprolactam, which is monomer for nylon-6. In this work, a novel and supported phosphoric acid modified TiO2 catalyst (TiPO/SiO2) had been successfully prepared for the catalytic oxidation of cyclohexylamine to cyclohexanone oxime. The results revealed that the supported TiPO/SiO2 catalyst exhibited promising catalytic activity and stability. Under the optimized reaction conditions, 49.4% of cyclohexylamine conversion with 87.8% of selectivity to cyclohexanone oxime was achieved over 20%TiPO/SiO2. The characterization results indicated that the TiPO/SiO2 possessed the abundant surface hydroxyls. XPS and DFT calculations verified that the surface titanium hydroxyls (Ti-OH) on TiPO/SiO2 were acted as the main catalytic active sites for activating cyclohexylamine. In situ FT-IR revealed the possible catalytic reaction pathway of cyclohexylamine with oxygen over TiPO/SiO2. The calculated energy profiles for the aerobic oxidation of cyclohexylamine showed that the energy barrier for NH bond cleavage was lower than that of α-CH bond cleavage, resulting in cyclohexanone oxime as main product. The present work afforded the new insights into the selective oxidation of cyclohexylamine to cyclohexanone oxime over functional TiPO/SiO2 catalyst, and has important industrial application prospects.

On the Stereochemistry of the NH Bond Activation of Ammonia or Amines by Disilenes: Predictability.

The stereochemistry of the addition of NH3 to the stereoisomers of 1,2-di-tert-butyl-1,2-bis(2,4,6-triisopropylphenyl)disilene (Z-5 or E-5) is 100 % stereospecific giving two isomeric disilylamines 6 and 7, respectively, derived from syn-addition to the stereoisomeric disilenes. Variable Time Normalization Analysis studies of the reaction of tetramesityldisilene (3) with isopropylamine (iPrNH2) revealed that the order in both amine and disilene is 1. The kinetic isotope effect for the addition of iPrNH2/iPrND2 to tetramesityldisilene was determined to be 3.04 ± 0.06 at 298 K, a primary KIE, indicating that the proton is transferred in the rate determining step. Competition studies between the addition of PrNH2 and iPrNH2 to tetramesityldisilene resulted in the exclusive formation of the PrNH2 adduct consistent with a nucleophilic addition. Computational studies of the mechanism of the addition of ammonia to E-5 revealed the lowest energy pathway involves the formation of the donor adduct derived from syn-addition, followed by intramolecular syn-transfer of the proton. The results of this studyallow for a refinement of our understanding of the mechanism of this important fundamental reaction in disilene chemistry, and allow us to understand our ability to reliably predict the stereochemical outcomes of future NH σ-bond activation reactions.

Strengthening spillover hydrogenation of quinoline compounds over platinum-encapsulated amorphized HA zeolite catalyst

Hydrogen spillover has been widely used in heterogeneous catalysis, yet how to explore the potential of catalyst support to further promote catalytic function of hydrogen spillover has rarely been investigated. Herein, platinum encapsulated into amorphized HA zeolite (denoted as Pt@HA) with generated hydroxyl groups was used as model catalyst to study the role of HA zeolite support on the promotion of catalytic performance in hydrogenation of quinolines to tetrahydroquinolines. Benefiting from small pore size of amorphized HA zeolite to prevent direct interaction of quinoline with encapsulated platinum, Pt@HA showed good catalytic selectivity in this transformation through hydrogen spillover. This remarkable catalytic selectivity was resulted from the interaction of hydroxyl groups at surface of HA zeolite with pyridine moiety through the formation NH bond to facilitate adsorption to make much lower apparent activation energy of Pt@HA for hydrogenation of pyridine moiety than that of benzene moiety, thus exhibiting enhanced catalytic selectivity.

A theoretical investigation of the catalytic decomposition of hydroxylamine nitrate on Ir(1 1 0) surface

Hydroxylamine nitrate (HAN) based propellant, with high energy performance and non-toxic, is regarded as an ideal propellant for monopropellant rocket engine. Density functional theory calculation was carried out to investigate the catalytic decomposition of HAN on Ir(110) surface. The optimized adsorption configurations and decomposition pathways of HAN on Ir(110) were calculated. Four different adsorption configurations and their decomposition pathways over Ir(110) have been found. The transformation of H from HNO3 to NH2OH happens in all adsorption configurations. In most situations, the decomposition of HAN starts with the scission of NO bond in NH3OH+ group. NH, OH, H2O and NO2 are the decomposition product. Compared with the barrier energy of each elementary reaction, the scission of NO bond in NO3– group is key to the decomposition rate of HAN. Among all products, NO2 and NH can be decomposed into N, O and H by scission of NO bond and NH bond.

Low loss SiN films for integrated photonics deposited by PVD at low temperature

Integration of SiN films with Si photonics platforms is attractive for the 3D integration of multiple waveguide levels in optical routing circuits. This paper reports on the optical characterization of SiN films deposited by PVD and PECVD with the STMicroelectronics 300 mm Photonic R&D platform at CMOS-compatible temperatures. SiN deposition was engineered to reduce the propagation losses caused by 2nd harmonic vibrational absorption of NH bonds.

Hydrogen production from ammonia decomposition catalyzed by Ru nano-particles in alkaline molecular sieves under photothermal conditions

Because the high electron cloud density around Ru is favorable for ammonia decomposition, gallium addition to it resulted in an alkaline molecular sieve carrier with a large specific surface area. It was revealed that GaOH not only elevated the electron cloud density near the active center of Ru but also encouraged NH bond breaking and hydrogen atoms’ binding on the catalyst surface. Furthermore, the molecular sieve's regular pore structure strongly inhibited the growth of Ru particles within it, resulting in a high degree of mono-dispersion of Ru nanoparticles and a reduction in the average particle size of the Ru active center to < 3 nm. For TOF >1, the above two factors combined to decrease the ammonia decomposition temperature to < 450 °C. Furthermore, under photothermal synergistic catalysis, the hydrogen production rate via ammonia decomposition was further elevated, and the reaction temperature was further decreased to < 380 °C with TOF > 1. In situ UV photoelectron spectroscopy clarified that the hydrogen atom concentration on Ru increased during photothermal catalysis. According to the FT-IR analysis of the surface intermediate of NH/NH2 formed by ammonia decomposition, photothermal synergistic catalysis can weaken the NH bond compared with pure heating, making it easier for H atoms to combine and form H2. The test results of the correlation between activation energy, reaction rate, and ammonia partial pressure show that, when compared to pure thermal catalysis, photothermal catalysis does not substantially alter the reaction path. The primary reason behind the increased hydrogen production rate of ammonia decomposition by photothermal catalysis was the thermal effect of the light source.