Functionalization of hydroxyl terminated polybutadiene with biologically active fluorescent molecule

A biologically active molecule, 2-chloro-4,6-bis(dimethylamino)-1,3,5-triazine (CBDT), has been covalently attached at the terminal carbon atoms of the hydroxyl terminated polybutadiene (HTPB) backbone. The modification of HTPB backbone by CBDT molecule does not affect the unique physico-chemical properties such as fluidity, hydroxyl value and microstructure of the parent HTPB. The formation of hydrogen bonding between the terminal hydroxyl groups and the nitrogen atoms of triazine moiety is the driving force for the terminal attachment chemistry. The functionalized HTPB (HTPB-CBDT) shows a strong fluorescence emission at 385 nm.     

Hydrogen and nitrogen effects on optical and structural properties of amorphous carbon

Two series of amorphous carbon alloys were deposited by reactive sputtering using a graphite target and argon as a sputtering gas. The effect of hydrogen or nitrogen on the structure of amorphous carbon was investigated using photothermal deflection spectroscopy (PDS), UV–Vis–near infrared spectroscopy, Fourier Transform Infrared (FT-IR), Raman and Photoluminescence (PL) techniques. The change in the structure of hydrogenated amorphous carbon (a-C:H) is due to the fact that H incorporation favours the formation of sp³ sites. In fact, the hydrogen incorporation relaxes the structure enough to improve electronic properties by increasing the number of terminal bonds. In the amorphous carbon nitride (a-CN) films, the lone pairs belonging to the nitrogen atoms are important in determining the optical properties of the films. The nitrogen alters the structure of carbon and creates cavities to be responsible for hydroxyl (OH) inclusions.     

Halogen bonding: Recent advances

Halogen bonding (XB), as a directional interaction between covalently bound halogen atoms (XB donor) and Lewis bases (A, XB acceptor), has been recently intensively investigated as a powerful tool in crystal engineering. After a short review on the origin and general features of halogen bonding, current developments towards (i) the elaboration of three-dimensional networks, (ii) the interaction with anionic XB acceptors, (iii) its identification in biological systems and (iv) the formation of liquid crystal phases will be described. Theoretical analyses, statistical studies and experimental electron density determinations converge to describe halogen bonding as a relatively weak structure directing tool, when compared with hydrogen bonding. However, when the halogen atom is strongly activated as in iodoperfluorinated molecules or cationic aromatic systems can halogen bonding act as an efficient and reliable structure directing tool.     

Nature of hydrogen bonding of water molecules in aqueous solutions of glycerol by attenuated total reflection (ATR) infrared spectroscopy

Attenuated total reflection infrared (ATR-IR) spectroscopy was performed on glycerol/water solutions in order to gain a better understanding of the strong hydrogen bonding of glycerol as a humectant. The OH stretching band after eliminating the contribution of glycerol OH in the glycerol/water solutions was decomposed using three Gaussian components. With increasing glycerol concentrations up to 50 volume %, the decrease of the 3428 cm(-1) component (middle H-bond component) and the increase of the 3562 cm(-1) component (longer H-bond component) suggested the breaking of H bonds among water molecules. On the other hand, the 3242 cm(-1) component (shorter H-bond component) remained unchanged. It was expected that water molecules surrounding glycerol molecules are retained by strong H bonding between H atoms of water and O atoms in C-O of glycerol when aqueous solutions containing glycerol are introduced in human skin.     

Design of nanoscale molecular wire based on diphenylacetylene: Role of linkage

Theoretical investigation has been performed on electron transport properties of diphenylacetylene-based molecules sandwiched between two gold surfaces. Different linkers such as sulfur, nitrogen, oxygen, CS, CO, CN, NS, NO and NN have been considered to study the role of linkage in the conduction properties of the molecular wire. The charge transfer across the metal–molecule and bonding nature at the interfacial contact are illustrated by natural bond orbital analysis. It is found that Au can covalently bond to diphenylacetylene through nitrogen or sulfur linkages while its weak interaction through oxygen linkage has non-covalent character in nature. The dependence of the molecular electronic structure of the gold–molecule complexes on the external electric field has been also studied. The electronic conduction has been analyzed from the change in the shape of molecular orbitals and the evolution of the HOMO–LUMO gap of the molecule-gold complexes under the influence of the electric filed.     

Molecular orbital calculations of hydrogen storage in carbon and boron nitride clusters

Hydrogen gas storage ability in carbon and boron nitride (BN) clusters was investigated by molecular orbital calculations. From single point energy calculations, H₂ molecules would enter from hexagonal rings of C₆₀ and B₃₆N₃₆ clusters and octagonal rings of B₂₄N₂₄ cluster because of lower energy barrier. Chemisorption calculation of hydrogen for BN clusters showed that hydrogen bonding with nitrogen atoms was more stable than that with boron atoms. Stability of H₂ molecules in BN clusters seems to be higher than that of carbon clusters.     

PAN基ACF的结构表征-XPS与元素分析

采用Ｘ射线光电子能谱与元素分析研究了聚丙烯腈基活性炭纤维的表面与本体的元素组成,相对含量以及表面含氧官能团的类型。实验结果表明：ＰＡＮ基ＡＣＦ的主体元素组成为Ｃ、Ｏ、Ｎ、Ｈ。ＡＣＦ的表面Ｃ含量大于本体平均Ｃ含量,表面氧含量与Ｏ／Ｃ比小于本体氧含量与Ｏ／Ｃ比。其中Ｃ元素大多以类石墨中性碳形式存在,本体与表面碳氧基团则以羟基、醚基为主并伴有一定数量的羰基、羧基、内酯基等。实验表明可采用ＸＰＳ技术定量研究ＡＣＦ表面官能团的组成、类型、变化与数量。     

Chemical and photoluminescence analyses of new carbon-based boron oxynitride phosphors

Analyses of newly developed carbon-based boron oxynitride phosphors using an electron energy-loss spectrometer and a spectroflurophotometer were carried out. The results showed that the prepared phosphor powder has covalently bonded boron, nitrogen, and oxygen atoms with a soft carbon framework. Photoluminescence characterization revealed that the resultant phosphor has a direct bandgap transition with defect broadened band edges, resulting in a high quantum efficiency, because the atomic distances of the phosphor are smaller than those of conventional carbon-based boron nitride compounds, which have an indirect bandgap transition and a low quantum efficiency. The atomic distances of the phosphor are smaller owing to the presence of oxygen atoms, which have a higher electron affinity and a smaller covalent bond radius compared with boron, carbon and nitrogen.     

Theoretical and spectroscopic investigations on the structure and bonding in B-C-N thin films

In this study, we have synthesized boron, carbon, and nitrogen containing films using RF sputter deposition. We investigated the effects of deposition parameters on the chemical environment of boron, carbon, and nitrogen atoms inside the films. Techniques used for this purpose were grazing incidence reflectance-Fourier-transform infrared spectroscopy (GIR-FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). GIR-FTIR experiments on the B-C-N films deposited indicated presence of multiple features in the 600 to 1700 cm^− 1 range for the infrared (IR) spectra. Analysis of the IR spectra, XPS and the corresponding EELS data from the films has been done in a collective manner. The results from this study suggested even under nitrogen rich synthesis conditions carbon atoms in the B-C-N films prefer to be surrounded by other carbon atoms rather than boron and/or nitrogen. Furthermore, we have observed a similar behavior in the chemistry of B-C-N films deposited with increasing substrate bias conditions. In order to better understand these results, we have compared and evaluated the relative stability of various nearest-neighbor and structural configurations of carbon atoms in a single BN sheet using DFT calculations. These calculations also indicated that structures and configurations that increase the relative amount of C-C bonding with respect to B-C and/or C-N were energetically favorable than otherwise. As a conclusion, carbon tends to phase-segregate in to carbon clusters rather than displaying a homogeneous distribution for the films deposited in this study under the deposition conditions studied.     

Effects of hydroxyl group distribution on the reactivity, stability and optical properties of fullerenols

We investigate the impact of hydroxyl groups on the properties of C(60)(OH)(n) systems, with n = 1, 2, 3, 4, 8, 10, 16, 18, 24, 32 and 36 by means of first-principles density functional theory calculations. A detailed analysis from the local density of states has shown that adsorbed OH groups can induce dangling bonds in specific carbon atoms around the adsorption site. This increases the tendency to form polyhydroxylated fullerenes (fullerenols). The structural stability is analyzed in terms of the calculated formation enthalpy of each species. Also, a careful examination of the electron density of states for different fullerenols shows the possibility of synthesizing single molecules with tunable optical properties.     

Preferential adsorption followed by spontaneous desorption of 1-octadecanol at a solution/graphite interface

The dynamical behavior of adsorption/desorption of 1-octadecanol on graphite was investigated by scanning tunneling microscopy under the existence of 3-imino-4,5,6,7-tetrachloroisoindolin-1-one (ITCII) in a 1-phenyloctane solution. The monolayer of 1-octadecanol was first formed preferentially, as it was the rich component, with many domains at the solution/graphite interface. The molecules at the domain boundaries were then spontaneously replaced by the ITCII molecules, keeping the hydrogen bonding of the OH head groups of 1-octadecanol. The driving force of this replacement can be explained by the difference in heats of adsorption per unit area between those two molecules.     

Thermal stability of magnetron sputtering amorphous carbon nitride films

Magnetron sputtered amorphous carbon nitride films were annealed at different temperatures (450-900°C) and time (30-120 min). Compositional, bonding structural and surface morphological modifications of the films were characterized by Fourier transformation infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy. The as-deposited film was found to have nitrogen content of 30 at%, and the carbon atoms were bonded to nitrogen atoms in the chemical structure state of CN, CN and CN bonds. The FTIR and XPS results showed that the films were thermally stable without an obvious change in the films as annealing temperature was lower than 600°C. The relative intensity ratio of CN over CN bonds reached a maximum at annealing temperature of 750°C, and then decreased gradually at annealing temperature up to 900°C. The CN bonds in the films decreased with the increase of annealing temperature and eliminated completely at annealing temperature of 900°C. These results revealed that annealing caused a substantial decrease in the number of weak bonds between carbon and nitride atoms. The CN bonds have higher thermal stability than CN bonds and CN bonds in the films. Simultaneously annealing also led to the formation of a large fraction graphitic-like carbon in the films while nitrogen escaped from the film. Besides, the surface roughness of the films increased with annealing temperature. However, when annealing time was increased from 30 to 120 min at annealing temperature of 750°C, only a slight effect of the annealing time on composition, bonding structure and the surface roughness of the films was observed.     

双模聚氨酯交联体系的力学性能

以端羟基聚丁二烯(HTPB)、环氧乙烷-四氢呋喃共聚醚(PET)以及聚叠氮缩水甘油醚(GAP)为粘合剂,多异氰酸酯(N100)、异佛尔酮二异氰酸酯(IPDI)为固化剂,三羟甲基丙烷(TMP)为交联剂,制备了PETS/PETL/N100、GAP/PETL/N100、GAP/PET/IPDI/TMP、GAP/HTPB/IPDI/TMP四种双模聚氨酯交联体系,研究了双模网络对聚氨酯弹性体力学性能的影响。结果表明,双模体系较之于短链单模体系,力学性能有了较大的改善。双模聚氨酯交联体系力学性能的提高主要是非仿射变形的结果,非仿射变形程度主要取决于交联点之间的氢键数。单组分固化反应速率的差异对双模体系的力学性能影响较大。     

X-ray-diffraction characterization of Pt(111) surface nanopatterning induced by C60 adsorption

Understanding the adsorption mechanisms of large molecules on metal surfaces is a demanding task. Theoretical predictions are difficult because of the large number of atoms that have to be considered in the calculations, and experiments aiming to solve the molecule-substrate interaction geometry are almost impossible with standard laboratory techniques. Here, we show that the adsorption of complex organic molecules can induce perfectly ordered nanostructuring of metal surfaces. We use surface X-ray diffraction to investigate in detail the bonding geometry of C(60) with the Pt(111) surface, and to elucidate the interaction mechanism leading to the restructuring of the Pt(111) surface. The chemical interaction between one monolayer of C(60) molecules and the clean Pt(111) surface results in the formation of an ordered sqrt[13] x sqrt[13]R13.9 degrees reconstruction based on the creation of a surface vacancy lattice. The C(60) molecules are located on top of the vacancies, and 12 covalent bonds are formed between the carbon atoms and the 6 platinum surface atoms around the vacancies. In-plane displacements induced on the platinum substrate are of the order of a few picometres in the top layer, and are undetectable in the deeper layers.     

Fe Isolated Single Atoms on S,N Codoped Carbon by Copolymer Pyrolysis Strategy for Highly Efficient Oxygen Reduction Reaction

Heteroatom‐doped Fe‐NC catalyst has emerged as one of the most promising candidates to replace noble metal‐based catalysts for highly efficient oxygen reduction reaction (ORR). However, delicate controls over their structure parameters to optimize the catalytic efficiency and molecular‐level understandings of the catalytic mechanism are still challenging. Herein, a novel pyrrole–thiophene copolymer pyrolysis strategy to synthesize Fe‐isolated single atoms on sulfur and nitrogen‐codoped carbon (Fe‐ISA/SNC) with controllable S, N doping is rationally designed. The catalytic efficiency of Fe‐ISA/SNC shows a volcano‐type curve with the increase of sulfur doping. The optimized Fe‐ISA/SNC exhibits a half‐wave potential of 0.896 V (vs reversible hydrogen electrode (RHE)), which is more positive than those of Fe‐isolated single atoms on nitrogen codoped carbon (Fe‐ISA/NC, 0.839 V), commercial Pt/C (0.841 V), and most reported nonprecious metal catalysts. Fe‐ISA/SNC is methanol tolerable and shows negligible activity decay in alkaline condition during 15 000 voltage cycles. X‐ray absorption fine structure analysis and density functional theory calculations reveal that the incorporated sulfur engineers the charges on N atoms surrounding the Fe reactive center. The enriched charge facilitates the rate‐limiting reductive release of OH* and therefore improved the overall ORR efficiency.     

Synthesis of fluorescent carbon nanoparticles directly from active carbon via a one-step ultrasonic treatment

Water-soluble fluorescent carbon nanoparticles were synthesized directly from active carbon by a one-step hydrogen peroxide-assisted ultrasonic treatment. The carbon nanoparticles were characterized by transmission electron microscopy, optical fluorescent microscopy, fluorescent spectroscopy, Fourier transform infrared spectroscopy and ultraviolet-visible spectrophotometer. The results showed that the surface of carbon nanoparticles was rich of hydroxyl groups resulting in high hydrophilicity. The carbon nanoparticles could emit bright and colorful photoluminescence covering the entire visible-to-near infrared spectral range. Furthermore, these carbon nanoparticles also had excellent up-conversion fluorescent properties.     

Grafting electrosprayed silica microspheres on cellulosic textile via cyanuric chloride reactive groups

A novel method of covalently grafting solid or hollow microcapsules on cellulosic textiles was developed by surface functionalisation of capsules with reactive triazine moieties. Demonstrative silica microspheres, with 454 nm average particle size, were developed by electrospraying silica sol prepared via sol–gel process. The chemical–physical properties of submicron particles were characterised by Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TGA) and scanning (SEM) and transmission electron microscopy (TEM). As a potential process towards functional textiles, the micro/nanosphere surface was modified with chlorotriazine ligands in a two-step procedure to react with the hydroxyl groups in cellulose under mild conditions. The first amine functionalisation was demonstrated by evaluation with FTIR and silicon-29 nuclear magnetic resonance (²⁹Si-NMR), as well as using TGA. Subsequent chemical functionalisation of an amine–silica surface with triazine moieties was analysed by FTIR, proton solid-state NMR spectroscopy (¹H-NMR) and TEM coupled to an X-ray detector. Finally, the covalent bonding of silica nanoparticles to cellulose was performed under simulated dying conditions and it was evaluated by SEM in combination to energy dispersive X-ray spectroscopy.     

Fenton-enhanced gamma-radiolysis of cyanuric acid

Degradation of cyanuric acid (OOOT), a stable end product of oxidative decomposition of atrazine, is investigated in a combined field of gamma radiolysis and fenton reaction. The reaction of hydroxyl radical (OH) at pH 6 was carried out by irradiating N(2)O saturated aqueous solutions containing OOOT (1 x 10(-3) mol dm(-3)), and this resulted only a marginal degradation (20%). However, when the same reaction was carried out in the presence of varying concentrations of ferrous sulfate ((5-10)x10(-5) mol dm(-3)), the decay of OOOT has been enhanced to more than 80%. This decay followed a first order kinetics. Nearly similar effects were observed with another triazine derivative, 2,4-dioxohexahydro-1,3,5-triazine (DHT). Two major reaction mechanisms are proposed for the enhanced decay of OOOT. The formation of unstable hydroxyl radical adducts from the reaction of .OH which is the result of gamma radiolysis and the Fenton reaction (resulting from the reaction of the added Fe(II) and of the H(2)O(2) from the radiolysis of water), is proposed as the first mechanism. The second mechanism, which is likely the major contributor to degradation, is proposed as the reaction of a nucleophilic adduct, Fe(II)OOH, which could directly react with the electron deficient triazine ring. It is highlighted that such degradation reactions must be explored for the complete degradation of the byproducts of the oxidative decomposition of atrazine.     

Understanding Defect‐Stabilized Noncovalent Functionalization of Graphene

The noncovalent functionalization of graphene by small molecule aromatic adsorbates, phenanthrenequinone (PQ), is investigated systematically by combining electrochemical characterization, high‐resolution interfacial X‐ray scattering, and ab initio density functional theory calculations. The findings in this study reveal that while PQ deposited on pristine graphene is unstable to electrochemical cycling, the prior introduction of defects and oxygen functionality (hydroxyl and epoxide groups) to the basal plane by exposure to atomic radicals (i.e., oxygen plasma) effectively stabilizes its noncovalent functionalization by PQ adsorption. The structure of adsorbed PQ molecules resembles the graphene layer stacking and is further stabilized by hydrogen bonding with terminal hydroxyl groups that form at defect sites within the graphene basal plane. The stabilized PQ/graphene interface demonstrates persistent redox activity associated with proton‐coupled‐electron‐transfer reactions. The resultant PQ adsorbed structure is essentially independent of electrochemical potentials. These results highlight a facile approach to enhance functionalities of the otherwise chemically inert graphene using noncovalent interactions.     

Selective Chemical Modification of Graphene Surfaces: Distinction Between Single‐ and Bilayer Graphene

Graphene modifications with oxygen or hydrogen are well known in contrast to carbon attachment to the graphene lattice. The chemical modification of graphene sheets with aromatic diazonium ions (carbon attachment) is analyzed by confocal Raman spectroscopy. The temporal and spatial evolution of surface‐adsorbed species allows accurate tracking of the chemical reaction and identification of intermediates. The controlled transformation of sp² to sp³ carbon proceeds in two separate steps. The presented derivatization is faster for single‐layer graphene and allows controlled transformation of adsorbed diazonium reagents into covalently bound surface derivatives with enhanced reactivity at the edge of single‐layer graphene. On bilayer graphene the derivatization proceeds to an adsorbed intermediate, which reacts slower to a covalently attached species on the carbon surface.