Effect Of Chemical Functionalization Research Articles

Chemical functionalization of low-buckled SiGe monolayer: Effects on the electronic and magnetic properties

Surface modification has been widely employed to modify fundamental properties of two-dimensional (2D) materials and create new multifunctional candidates for practical applications. In this work, the effects of chemical functionalization on silicon germanide (SiGe) monolayer have been investigated using first-principles calculations. Pristine monolayer exhibits good dynamical stability and a Dirac cone at K point in the band structure. The nearly semimetallic nature and absence of magnetic properties represent great challenge for SiGe monolayer applications. Our results show that these deficiencies can be overcome with oxygenation and hydrogenation processes. Oxygen (O) and hydrogen (H) atoms prefer to be adsorbed on-top of bridge and Si atom, respectively. The non magnetic nature is preserved under oxygenation, however a significant band gap up to 1.35 eV can be introduced depending on the O concentration. Meanwhile, the ferromagnetic semiconducting is induced by hydrogenation, where magnetic properties are produced mainly by Ge atoms, regardless the H coverage. In fact, efficient methods have been introduced to make SiGe monolayer promising 2D material for optoelectronic and spintronic applications through adsorbing O and H atoms.

Buckling of functionally graded hydrogen-functionalized graphene reinforced beams based on machine learning-assisted micromechanics models

Nanocomposite reinforced with functionalized graphene is a novel class of high-performance materials with great potential in developing advanced lightweight structures in a wide range of engineering applications. However, accurate estimation of its material properties at different temperature conditions remains a great challenge as existing micromechanics models fail to capture the effects of chemical functionalization and temperature. This paper develops machine learning (ML)-assisted micromechanics models by employing genetic programming (GP) algorithm and molecular dynamics (MD) simulation to address this key scientific problem. The well-trained ML-assisted Halpin-Tsai model and rule of mixture can accurately and efficiently predict the temperature-dependent material properties including Young's modulus, Poisson's ratio, coefficient of thermal expansion (CTE), and density of hydrogen-functionalized graphene (HFGr) reinforced copper nanocomposites with high coefficients of determination (R2). Then, the buckling behavior of functionally graded (FG) HFGr nanocomposite beams is studied with the aid of the ML-assisted micromechanics models. A detailed parametric study is performed with a particular focus on the effects of hydrogenation percentage, graphene content, and temperature on the buckling performance of the FG-HFGr beam. Results show that bonding more hydrogen functional groups on the HFGr can effectively improve the buckling resistance of the beam.

Enhancing the Surface Reactivity of Black Phosphorus on Hydrogen Evolution by Covalent Chemistry

Covalent functionalization has been demonstrated to be an effective strategy to improve the stability of monolayer black phosphorus (BP); however, the effect of chemical functionalization on the ca...

Versatile Synthetic Platform for Polymer Membrane Libraries Using Functional Networks

Poly(ethylene glycol) (PEG) diacrylate copolymer networks containing pentafluorophenyl active esters can be quantitatively substituted with a wide variety of primary amines, enabling the development of a versatile synthetic platform for the preparation of polymer hydrogel and membrane libraries. By tuning the starting network, a high degree of control over cross-linking density, water uptake, and functional group incorporation can be reproducibly achieved, which is vital for elucidating structure–property relationships in ion transporting membranes. From the same cross-linked scaffold, a diversity of basic, acidic, and solute-chelating moieties were obtained through functionalization, which allows for tailored uptake of basic and acidic organic dyes and metal chloride salts. Ion permeation and sorption measurements for a series of polymer networks with controlled cross-linking density and varied imidazole grafting densities illustrate the ability of this platform to isolate the effect of chemical functionality on ion transport from the effects of cross-linking density and water content.

Covalently bonded surface functional groups on carbon nanotubes: from molecular modeling to practical applications.

The aim of this work was to investigate how chemical functionalization affects the electronic properties of multi-walled carbon nanotubes, altering the electrophoretic deposition process: a method of choice for the fabrication of high quality, all-carbon nanotube (CNT) layers. Wet chemistry methods were applied to modify the surfaces of CNTs by insertion of various oxygen- and nitrogen-containing groups. Transmission electron microscopy revealed no significant changes in the material morphology, while X-ray photoelectron spectroscopy and Raman spectroscopy showed that changes in the chemical composition did not translate to the changes in the structure. Molecularly modelled optimized surface functional group geometries and electron density distributions allowed the calculation of the dipole moments (-COOH = 0.77; -OH = 1.65; -CON(CH3CH2)2 = 3.33; -CONH2 = 2.00; -NH2 = 0.78). Due to their polarity, the introduction of surface functional groups resulted in significant modifications of the electronic properties of CNTs, as elucidated by work function measurements via the Kelvin method and ultraviolet photoelectron spectroscopy. The work function changed from 4.6 eV (raw CNTs) to 4.94 eV for the -OH functionalized CNTs and 4.3 eV for the CNTs functionalized with -CON(CH3CH2), and was inversely proportional to the dipole moment values. Finally, using CNT dispersions, electrophoretic deposition was conducted, allowing the correlation of the work function of CNTs and the measured electrophoretic current with the impact on the deposits' qualities. Thus, a rational background for the development of carbon-based biomaterials was provided.

Functionalization of carbon nanomaterials: Dispersion and thermal conductivity measurement

Carbon nanomaterials (CNs) have attracted greater deal of interest due to their precise and remarkable bodily properties. The present painting proposes to observe the Multi-walled Carbon Nanotube (MWCNT) and Multi-walled Carbon Nano-coil (MWCNC) as capability carbon nanomaterials for the nanofluids. Our effort has been devoted to analyze structural changes, dispersion and thermal conductivity measurement. Covalent and non-covalent modifications of CNs were investigated on the way to obtain accurate dispersion and conductivity.The outcomes demonstrated that very much scattered Cu/MWCNTs nanofluids with shifting grouping of Cu/MWCNTs can be combined utilizing the current technique. A most extreme warm conductivity at a low volume portion of Cu/MWCNTs has come about because of the homogeneous scattering of Cu finished MWCNTs in base liquids and arrangement of increasingly hydrophilic MWCNTs because of the connection of oxygen containing utilitarian gatherings prompting a decent co-operations of MWCNTs with another. Oxidative adjustment of nanomaterial delivered about by using corrosive remedy and achieve of oxidative ultra-sonication on improvement of beneficial at the carbon nanomaterials became explored for numerous timeframes. Structural stability has been monitored through thermo gravimetric evaluation (TGA) and morphological characterization through scanning electron microscopy (SEM). Hydrophilic effect of chemical functionalization on CNs turned into investigated by means of FT-IR and Raman spectroscopy. The heating conductivity execution of CN based totally nanofluids turned into concentrated with differed quantity quantities and temperature not exceeding (25–50 °C).

Effects of defects on the interfacial shear characteristics between graphene and poly (methyl methacrylate)

AbstractPullout simulations were conducted to investigate the interfacial shear properties between defective graphene (DGr) and polymethyl methacrylate (PMMA) through molecular dynamics simulations with ReaxFF reactive force fields. The effects of number of defects (Stone‐Wales [SW] and double‐vacancy [DV] defects) were investigated. Our results showed that these two types of defects can obviously enhance the interfacial shear strengths of DGr /PMMA nanocomposites. And the DV defects have a greater contribution to the interfacial shear strength enhancement compared to the SW defects. Analysis of the morphology of DGr indicated that surface roughness, which was induced by defects, plays an important role in enhancing the interfacial shear strength at the interface between the DGr and PMMA. Moreover, the effects of chemical functionalization at the defect sites were also investigated. We observed that the CO bonds of functional groups (hydroxyls) at defect sites inclined from the datum plane (z = 0 plane) of the graphene sheet. The inclination of CO bonds, which weakened the mechanical interlocking between functional graphene and PMMA matrix, differently influenced by the DV defect and SW defect.

Toughening of graphene-based polymer nanocomposites via tuning chemical functionalization

Previous experiments on the mechanics of graphene-based polymer nanocomposites report their mechanical properties far below theoretical predictions. A critical factor in this regard is the nature and strength of nanofiller/matrix interfacial bonding. Herein, beneficial effects of chemical functionalization on the interfacial mechanical properties of graphene-based polymer nanocomposites are investigated using complementary experiments and molecular dynamics (MD) simulations. We report that by tuning the extent and chemistry of the functionalized species, (approximately 10%), graphene-PMMA nanocomposites can achieve superior mechanical properties by improving the interfacial load transfer. Compared to pure PMMA, an increase of 46% in Young's modulus and 119% in energy absorbed per unit volume during fracture, respectively, were achieved for 10% functionalized nanocomposites. Such an increase in energy absorbed was caused by a transition in crack propagation mechanism from interfacial slippage to crack arresting behavior, owing to the enhanced interfacial bonding. MD simulations revealed that such a change in mechanism is caused by the formation of both hydrogen bond networks and physical entanglements at the interface. While the methodology can be applied for different nanocomposite systems, the present results may provide an avenue for more efficient design of graphene-based nanocomposite structures.

Lipid-functionalized porous oxide nanoparticles for acoustic imaging and site-directed therapy

While most US contrast agents are fluid-filled micro- or nanoparticles, their stability of fluid-filled particles is limited by inherent Laplace pressure and equilibrium with the surroundings. Here, I will present our work designing silica nanoparticles of ∼100 nm with specifically tailored surfaces that can nucleate the formation of ultrasound-responsive microbubbles under reduced acoustic pressures. I will discuss the underlying materials science behind their activity, the effects of chemical functionalization on acoustic contrast (with the potential for stimulus-responsiveness), and applications in imaging and directed mechanical cell killing.

Molecular dynamics study for CH4/H2S separation through functionalized nanoporous graphyne membrane

Molecular dynamics simulations were employed to investigate the effect of chemical functionalization and applied pressure on the CH4/H2S separation performance using graphyne as a membrane. A pore was created on the graphyne surface and then functionalized with hydroxyl group and fluorine. The number of methane and hydrogen sulfide molecules in the simulated systems was 100 molecules from each of them, which were placed between graphyne and graphene nanosheet as a barrier. The results indicated that nanoporous graphyne can be suitable membrane for gas separation, especially in the absence of applied pressure, which is an acceptable condition for gas separation systems.

Effect of chemical functionalization on charge transport of multiwall carbon nanotube

We have studied the effect of chemical functionalization on charge transport property of multiwall carbon nanotube (MWNT) down to the temperature 4.2 K and magnetic field up to 5 T. The resistivity ratio (ρr = [ρ(T)/ρ(100 K)]) increases with the increment of degree of functionalization at low temperature as the effect of inclusion of disorder in the samples. The variation of resistivity with temperature has been explained by 3D variable range hopping model and Coulomb gap Efros-Shklovskii model, and the result shows that higher degree of functionalization enhances the disorder induced electron-electron interaction. For all the measured temperature and degree of functionalization, MWNTs show negative magnetoresistance. Negative magnetoresistance has been explained by 3D weak localization model.

Edge functionalization of finite graphene nanoribbon superlattices

The effect of chemical functionalization on the electronic properties of graphene nanoribbon superlattices with zigzag and armchair terminations is investigated using the density functional theory. The calculated positive binding energies imply that all the considered structures are stable before and after chemical modifications. The superlattices with armchair edges are characterized by a wide energy gap while those with zigzag edges have a narrow energy gap. The energy gap in superlattices with armchair edges nearly independent of their length while it strongly decreases and almost closes in superlattices with zigzag edges. The energy gap is comparably sensitive to the width variations in both types of the superlattices. It was found that the electric dipole moment increases with increasing the width in the case of armchair while it oscillates in zigzag superlattices. The electric dipole moment can be enhanced by chemical functionalization with COOH and NH2 groups. The effect of this functionalization is moderate for the energy gap, but the adsorption of tetracyanoquinodimethane transforms the system from insulator (Eg = 2.66 eV) to a narrow band gap semiconductor (Eg = 0.25 eV). The adsorption energy of tetracyanoquinodimethane and tetrathiafulvalene molecules can be enhanced by chemical functionalization which makes graphene superlattices useful for sensor applications and wastewater treatment.

Effect of APTMS modification on multiwall carbon nanotube reinforced epoxy nanocomposites

In this present investigation, we have studied the effect of chemical functionalization, and mechanical dispersion of carbon nanotube (CNT) reinforced epoxy resin. The chemical function of the CNT has been done by silane treatment. Silane modification has been done first by acid treatment on ball-milled CNT followed by chemical treatment of amine-based silane. FTIR spectra exhibit that silane chemically interacts with the CNT and epoxy resin. Mechanical dispersion of CNT in the epoxy was performed in the planetary ball mill. Ball milled CNT shows some degree of exfoliation. Mechanical properties of ball-milled and silane modified CNT reinforced epoxy is characterized in terms of fracture toughness and tensile modulus. Silane-modified CNT/epoxy shows an increase of 38% and 42% compared to the neat resin for fracture toughness and tensile modulus values respectively. Increase in the mechanical properties for silane modified CNT/epoxy is due to the excellent adhesion between CNT-matrix as well as significant dispersion of CNT in the epoxy resin provided by silane molecule as observed from TEM images. AFM indentation on the nanocomposites exhibits the presence of CNT agglomerates through adhesion and corresponding modulus map at the nanoscale level. SEM images indicate an increase in surface roughness with CNT inclusion which relates to the existence of an extrinsic mechanism. Additionally, better adhesion between CNT and matrix due to silane modification indicate a higher Tg value of silane modified CNT/epoxy than ball milled CNT/epoxy.

Effect of chemical functionalization on the thermal conductivity of 2D hexagonal boron nitride

Hexagonal boron nitride nanosheets (h-BNNSs) are excellent candidates as fillers of polymer-based thermal interface materials for electronic packaging. Chemical functionalization of h-BNNSs is necessary to improve the dispersity of the h-BNNSs and reduce the interfacial thermal resistance (ITR) in the composites. However, though studied extensively, the thermal conductivity (TC) of the chemically functionalized h-BNNS/polymer composites is still well below expectations. Among the possible reasons, the TCs of the functionalized h-BNNSs themselves need to be considered thoroughly, as it has been shown that TC of graphene could be dramatically reduced to less than 10 W m−1 K−1 by point defects. Here, we investigate the TCs of hexagonal boron nitride (h-BN) monolayers covalently adsorbed with -OH and -O(CH2)4CH3 groups based on equilibrium molecular dynamics simulations. The TC of the functionalized h-BN decreases monotonically with the increasing concentration of adsorbed groups and tends to saturate at high concentrations. We surprisingly find that the almost-saturated TCs of the functionalized h-BN monolayers are still over 100 W m−1 K−1, about 25% of the value of the pristine h-BN monolayer. The different functional groups have a similar effect on the TCs, which are mostly determined by the extent of distortion of the local 2D structure, and the functionalization introduces no additional anisotropy to the TC. Therefore, we conclude that the chemically functionalized h-BNs themselves are sufficiently thermally conductive as fillers of composites, and the chemical functionalization should be encouraged, with the focus on digging into how to reduce the ITR more effectively.

Effect of Chemical Functionality on the Mechanical and Barrier Performance of Nanocellulose Films

In the present work, we have partially modified fibrils chemically to create a shell of derivatized cellulose that surrounds the crystalline core of native cellulose. Through the different modifications, we aimed at creating a toolbox to enable the properties of CNF materials and materials containing CNFs to be tuned to meet specific material demands. In total, nine different chemical modifications using different aqueous-based procedures were used as chemical pretreatments before CNF production through homogenization. Eight of these modifications included periodate oxidation with an average of 27% of the anhydroglucose units in the cellulose chain being cleaved into dialdehydes. The presence of aldehydes then facilitated a conversion to other functional groups. TEMPO oxidation was also performed, alone or combined with either periodate oxidation or periodate oxidation followed by borohydride reduction or chlorite oxidation. The nine different CNFs produced after chemical modifications were characterized ...

Effects of Chemical Functionalization of MWCNTs on the Structural and Physical Properties of Elastomeric Copolyetherester-based Composite Fibers

Elastomeric copolyetherester (CPEE)-based composite fibers incorporating various neat and functionalized multiwalled carbon nanotubes (MWCNTs) were prepared through a conventional wet-spinning and coagulation process. The influence of functionalized MWCNTs on the morphological features, and the thermal, mechanical properties and electrical conductivity of CPEE/MWCNT (80/20, w/w) composite fibers were investigated. FE-SEM images show that a composite fiber containing poly(ethylene glycol)-functionalized MWCNTs (MWCNT-PEG) has a relatively smooth surface owing to the good dispersion of MWCNT-PEGs within the fiber, whereas composite fibers including pristine MWCNTs (p-MWCNT), acid-functionalized MWCNTs (a-MWCNT), and ethylene glycol-modified MWCNTs (MWCNT-EG) have quite a rough surface morphology owing to the presence of MWCNT aggregates. As a result, the CPEE/MWCNT-PEG composite fiber exhibits noticeably increased thermal and tensile mechanical properties as well as a faster crystallization behavior, which stems from an enhanced interfacial interaction between the CPEE matrix and MWCNT-PEGs.

Tailoring water stability of cellulose nanopaper by surface functionalization.

Cellulose nanopaper (CNP) features appealing properties, including transparency, flatness, a low thermal expansion coefficient and thermal stability, often outperforming conventional paper. However, free-standing crystalline cellulose films usually swell in water or upon moisture sorption, compromising part of their outstanding properties. This remains a major problem whenever working in a water environment is required. Freestanding cellulose nanopaper is prepared by solution casting water suspensions of cellulose nanocrystals with an average width of 10 nm and an average aspect ratio of 28, isolated from Avicel by acid hydrolysis and extensively characterized by AFM and FE-SEM measurements and GPC detection of their degree of polymerization. We demonstrate by elemental analyses, FT-IR, Raman spectroscopy, XRD measurements and water contact angle detection that wet treatment with lauroyl chloride results in surface hydrophobization of nanopaper. The hydrophobized nanopaper, C12-CNP, shows a more compact surface morphology than the starting CNP, due to the effect of chemical functionalization, and presents enhanced resistance to water, as assessed by electrochemical permeation experiments. The new hydrophobized nanopaper is a promising substrate for thin film devices designed to work in a humid environment.

Tuning the Swing Effect by Chemical Functionalization of Zeolitic Imidazolate Frameworks.

Many zeolitic imidazolate frameworks (ZIFs) are promising candidates for use in separation technologies. Comprising large cavities interconnected by small windows they can be used, at least in principle, as molecular sieves where molecules smaller than the window size are able to diffuse into the material while larger molecules are rejected. However, "swing effect" or "gate opening" phenomena resulting in an enlargement of the windows have proven to be detrimental. Here, we present the first systematic experimental and computational study of the effect of chemical functionalization of the imidazole linker on the framework dynamics. Using high-pressure (HP) single-crystal X-ray diffraction, density functional theory, and grand canonical Monte Carlo simulations, we show that in the isostructural ZIF-8, ZIF-90, and ZIF-65 functional groups of increasing polarity (-CH3, -CHO, and -NO2) on the imidazole linkers provide control over the degree of rotation and thus the critical window diameter. On application of pressure, the substituted imidazolate rings rotate, resulting in an increase in both pore volume and content. Our results show that the interplay between the guest molecules and the chemical function of the imidazole linker is essential for directing the swing effect in ZIF frameworks and therefore the adsorption performance.

Evaluation of electrospun nanofibrous mats as materials for CO2 capture: A feasibility study on functionalized poly(acrylonitrile) (PAN)

We fabricated a new type of nanostructured materials for CO2 capture processes, based on poly (acrylonitrile), PAN, a polymer almost impermeable to CO2, but easily functionalizable and spinnable. The preparation involved amine functionalization of PAN powder, electrospinning of the powder to form a nanofibrous mat with a large surface area, and compression of the mat to obtain dense membranes for facilitated transport of humid CO2. The functionalization step was carried out with different routes: amination with hexamethylene diamine or ethylene diamine, and basic hydrolysis. The final amine content in the polymer could be tuned varying the reaction type and conditions, although high functionalization degrees led to crosslinking, which made the powder insoluble.The dry CO2 uptake was measured at various stages of the preparation, in order to assess separately the effect of chemical functionalization and surface area enhancement on the material capture ability. Such tests indicated that both chemical and morphological changes of the neat polymer enhanced the dry CO2 sorption capacity, although the increase of surface area yielded the largest improvement.CO2 permeation tests in humid conditions were carried out on the compacted membranes, indicating that the materials functionalized via direct amination exhibit a behavior compatible with the facilitated transport mechanism, with CO2 permeability reaching 83 Barrer, increasing by 17 times with respect to the dry state value, at a relative humidity of 50%. Membranes functionalized via hydrolysis did not show such a behavior, maybe because the amine functionalities were consumed by an unwanted reaction. The procedure can be further improved by optimizing each processing step, or changing the order of the steps. The electrospinning process seemed the key factor of the approach, as the large surface area of electrospun mats allowed to obtain membranes with a higher permeability than the original ones, and a large availability of amine groups useful for humid CO2 capture.

Thermal conductivity of penta-graphene: The role of chemical functionalization

Penta-graphene (PG) has recently been identified as a novel two-dimensional carbon allotrope comprising entirely of pure pentagons and possessing many unique properties beyond graphene. Herein we investigate the thermal conductivity of hydrogenated and oxidized PGs at different levels of coverage by using non-equilibrium molecular dynamics simulations. Our simulation results show that the oxidized PG possesses a higher thermal conductivity than the hydrogenated counterpart at the same coverage. Interestingly, both functionalized PGs exhibit an unusual down-and-up trend in the thermal conductivity with the increase of coverage level, and the fully functionalized PGs (at 100% coverage) possess almost the same thermal conductivity as the pristine PG. We further explore the underlying mechanisms for the coverage-dependent thermal conduction. Our work provides important insights into the effect of chemical functionalization on the thermal conductivity of this new carbon allotrope.