Non-covalent Functionalization Method Research Articles

Enhancement of oxygen evolution reaction by in situ growth PMo12@ZIF-67 on MWCNTs via perylene bisimide-based dispersant

The combination of metal organic frameworks (MOFs) and multi-walled carbon nanotubes (MWCNTs) can significantly improve their electrochemical performance. However, in most cases, chemical pre-treatment of MWCNTs is inevitable, which may compromise the ideal performance of the final composites. Herein, via a noncovalent functionalization method, PMo12@ZIF-67 was in situ grown on the surfaces of MWCNTs with the assistance of a new dispersant containing two triethylenetetramine (TETA) segments. In order to enhance the coordination of Co metal ions with the surface of MWCNTs, phenolic hydroxyl groups were incorporated into the dispersant through reaction with gallic acid (GA). After annealing, homogeneous CNT/Co6Mo6C2/Co composites were obtained, and they showed excellent performance on oxygen evolution reaction (OER). At a current density of 10 mA cm−2, the lowest overpotential is 263 mV, of which the performance is superior to that achieved by other in situ growth methods. The uniform distribution of coordination sites and subsequent in situ growth of MOFs on MWCNTs improved the electrical conductivity of the derivatives, thereby enhanced the utilization of catalytic active sites. This study presents a novel approach for synthesizing carbon-doped electrocatalytic materials, which demonstrates significant potential in various electrochemical applications.

Experimental investigation of an automobile radiator using carbon based hybrid nano coolant

Comprehensive experimentation on the heat transfer performance of a vehicle radiator with a novel hybrid nanofluid (HyNf) comprising Graphene nanoplatelets (GnP) and Multi-walled carbon nanotubes (MWCNT) nanoparticles in 1:1 ratio, dispersed in radiator coolant oil (base fluid), has been performed. Non-covalent functionalization method was implemented to prepare steady nanofluids for volume concentrations of 0.05%, 0.1%, 0.15%, 0.2%, 0.3%, 0.4%, and 0.5%. Tests were conducted for different nanofluid flow rates from 20 g/s to 100 g/s in 5 steps, three different nanofluid entry temperatures of 30 °C, 50 °C and 70 °C and three different air velocities viz. 1, 3 and 5 m/s. The enhancement in thermal conductivity (TC) was observed as 59% for 0.5 vol % compared to base fluid, which leads to an augmentation in the convective heat transfer coefficient (CHTC) of nanofluid. The maximum improvement in overall heat transfer coefficient (OHTC) was found as ∼ 124% at 0.5% volume concentration, 5 m/s air velocity, compared to the base fluid. A rise in the pressure drop is found as 23.72% compared to base fluid. Due to these enhanced heat transfer behaviours of the synthesized GnP-MWCNT/coolant oil HyNf, it can be an alternate to the existing coolant oil.

Effects of Non-covalent Functionalization and Initial Mixing Methods on SWNT/PP and SWNT/EVOH Composites.

We report that a simple, low-cost type of spray-freeze drying (SFD) significantly improves the dispersion of single-walled carbon nanotubes (SWNTs) in thermoplastic polymers. Conventional SFD requires costly specialized equipment and large amounts of material, both of which are impediments to laboratory research on nanomaterial composites. Our method uses more readily available equipment and can be adapted to use milligrams to grams of material. A household spray bottle containing an aqueous nanomaterial dispersion is used to spray the dispersion into a dish of liquid nitrogen. The resulting material is then lyophilized in a standard laboratory freeze dryer. The usefulness of this simplified method was explored by comparing the properties of polypropylene (PP) composites produced by this method to those produced by a previously reported rotary evaporation method in which the dispersion is vacuum-dried onto the polymer. The role of the initial dispersion state was explored by using pristine SWNTs as well as SWNTs stabilized by two common SWNT stabilizers: polyvinylpyrrolidone (PVP) and sodium dodecyl sulfate. Based on rheological, thermal, and morphological characterization, the porous friable structures produced by SFD resulted in better SWNT dispersion compared to composites produced by a previously reported rotary evaporation method. However, the PP/PVP-SWNT nanocomposites produced by both methods contained large aggregates. To verify that this aggregation behavior was the result of thermodynamic incompatibility between PP and PVP, ethylene vinyl alcohol (EVOH) nanocomposites containing PVP-SWNT were also produced using the SFD method. The results of this research show how a low-cost alternative to SFD along with careful consideration of compatibility is a promising approach to produce nanocomposites.

Synthesis and Characterization of Clarithromycin-Graphene Oxide for Antibacterial Drug Delivery

The conventional oral formulation of the antibacterial drug clarithromycin has always been a major challenging task to overcome due to its low bioavailability, short circulation half-life, poor aqueous solubility, and acidic instability inside the stomach. Therefore, targeted drug delivery system is one of the key solutions to overcome these pharmaceutical limitations. A study was conducted to formulate and optimize the clarithromycin loading efficiency of a novel nanoparticle-mediated drug delivery system based on graphene oxide as the carrier. The clarithromycin-graphene oxide nanohybrid was synthesized using a simple, non-covalent functionalization method and characterized by ultraviolet-visible and Fourier transform infrared spectroscopies. The drug loading efficiency of graphene oxide was estimated to be around 56.0 wt% and the Fourier transform infrared spectra suggested that clarithromycin was successfully conjugated onto graphene oxide as evidenced by the characteristic absorption peaks of both graphene oxide and clarithromycin. The findings herein strongly indicate that graphene oxide, as a multifunctional and versatile nanomaterial, can be a potential drug carrier for enhancing the pharmacokinetic profiles of poorly water-insoluble drugs like clarithromycin.&nbsp

Synthesis of carboxymethyl chitosan-functionalized graphene nanomaterial for anticorrosive reinforcement of waterborne epoxy coating

In this study, a carboxymethyl chitosan functionalized graphene (CMCS-rGO) nanomaterial was successfully synthesized in aqueous solution by non-covalent functionalization method. Fourier transform infrared, Raman, ultraviolet visible spectroscopy and thermogravimetric analysis confirmed that carboxymethyl chitosan had been successfully anchored on the surface of graphene. In addition, the CMCS-rGO was used as an anticorrosive nanofiller to be added to waterborne epoxy (EP) coatings to protect steel substrates. The corrosion protection behavior of all coatings was tested by electrochemical workstation, and the results proved that the incorporation of well-dispersed CMCS-rGO nanomaterials could significantly improve the anti-corrosion performance of waterborne epoxy coatings. Furthermore, even after 180 days of immersion, the impedance modulus value of the 0.2 % CMCS-rGO/EP at |Z|f =0.01 Hz was still approximately 2 orders of magnitude higher than that of the EP.

Recent Advances in Chemical Functionalization of 2D Black Phosphorous Nanosheets.

Owing to their tunable direct bandgap, high charge carrier mobility, and unique in‐plane anisotropic structure, black phosphorus nanosheets (BPNSs) have emerged as one of the most important candidates among the 2D materials beyond graphene. However, the poor ambient stability of black phosphorus limits its practical application, due to the chemical degradation of phosphorus atoms to phosphorus oxides in the presence of oxygen and/or water. Chemical functionalization is demonstrated as an efficient approach to enhance the ambient stability of BPNSs. Herein, various covalent strategies including radical addition, nitrene addition, nucleophilic substitution, and metal coordination are summarized. In addition, efficient noncovalent functionalization methods such as van der Waals interactions, electrostatic interactions, and cation–π interactions are described in detail. Furthermore, the preparations, characterization, and diverse applications of functionalized BPNSs in various fields are recapped. The challenges faced and future directions for the chemical functionalization of BPNSs are also highlighted.

Recent Advances in Characterization Techniques for the Interface in Carbon Nanotube-Reinforced Polymer Nanocomposites

The current state of characterization techniques for the interface in carbon nanotube-reinforced polymer nanocomposites is reviewed. Different types of interfaces that exist within the nanocomposites are summarized, and current efforts focused on understanding the interfacial properties and interactions are reviewed. The emerging trends in characterization techniques and methodologies for the interface are presented, and their strengths and limitations are summarized. The intrinsic mechanism of the interactions at the interface between the carbon nanotubes and the polymer matrix is discussed. Special attention is given to research efforts focused on chemical functionalization of carbon nanotubes. The benefits and disadvantages associated with covalent and noncovalent functionalization methods are evaluated, respectively. Various techniques used to characterize the properties of the interface are extensively reviewed. How the mechanical and thermal properties of the nanocomposites depend on the physical and chemical nature of the interface is also discussed. Better understanding and design of the interface at the atomic level could become the forefront of research in the polymer community. Potential problems going to be solved are finally highlighted.

Interest of molecular functionalization for electrochemical storage

Despite great interests in electrochemical energy storage systems for numerous applications, considerable challenges remain to be overcome. Among the various approaches to improving the stability, safety, performance, and cost of these systems, molecular functionalization has recently been proved an attractive method that allows the tuning of material surface reactivity while retaining the properties of the bulk material. For this purpose, the reduction of aryldiazonium salt, which is a versatile method, is considered suitable; it forms robust covalent bonds with the material surface, however, with the formation of multilayer structures and sp3 defects (for carbon substrate) that can be detrimental to the electronic conductivity. Alternatively, non-covalent molecular functionalization based on π–π interactions using aromatic ring units has been proposed. In this review, the various advances in molecular functionalization concerning the current limitations in lithium-ion batteries and electrochemical capacitors are discussed. According to the targeted applications and required properties, both covalent and non-covalent functionalization methods have proved to be very efficient and versatile. Fundamental aspects to achieve a better understanding of the functionalization reactions as well as molecular layer properties and their effects on the electrochemical performance are also discussed. Finally, perspectives are proposed for future implementation of molecular functionalization in the field of electrochemical storage.

Overall heat transfer coefficient improvement of an automobile radiator with graphene based suspensions

In the present work, we report the enhancement in overall heat transfer coefficient of an automobile radiator using graphene nanoplatelets based nanofluid as the coolant. Water-ethylene glycol mixture (70:30 by volume) was used as the base fluid and stable nanofluids were synthesized by non-covalent functionalization method with volume concentrations of graphene nanoplatelets varying from 0.1% to 0.5%. Experiments were performed in an automobile radiator for varying nanofluid mass flow rates viz. 12.5g/s, 25g/s, 37.5g/s, 50g/s, 62.5g/s and two nanofluid inlet temperatures viz. 35°C, 45°C and air velocity. For each condition the ambient air velocity was varied from 1m/s to 5m/s in steps of 1m/s. The convective heat transfer coefficient of nanofluid and overall heat transfer coefficient are found to increase with respect to mass flow rate, inlet temperature of nanofluid and graphene nanoplatelets loading. The improvement in convective heat transfer coefficient of nanofluid play a significant role in the enhancement of overall heat transfer coefficient. The maximum enhancement in OHTC with respect to concentration is found to be ∼104% at 35°C while it is found to be ∼81% at 45°C for 0.5vol%, 62.5g/s flow rate and 5m/s air velocity. Further, the pressure drop of nanofluids increases with increase in mass flow rate and graphene loading. The increase in pressure drop is significantly influenced by the mass flow rate than by graphene nanoplatelets loading.

Evaluation of chemical modification effects on DNA plasmid transfection efficiency of single-walled carbon nanotube-succinate- polyethylenimine conjugates as non-viral gene carriers.

Polyethylenimine (PEI) is a widely used non-viral vector for DNA delivery. One major obstacle of higher molecular weight PEIs is the increased cytotoxicity despite the improved transfection efficiency and numerous chemical modifications that have been reported to overcome this problem. Carbon nanotubes (CNT) are carbon nanomaterials capable of penetrating into cell membranes with no cytotoxic effects. Covalent and noncovalent functionalization methods have been used to improve their solubility in aqueous media. The idea of conjugating PEIs and CNT through different chemical bonds and linkers seems promising as it may result in highly effective carriers due to combination of the transfection ability of PEI with cell internalization of CNT. In this study, six different water-soluble PEI conjugates of single-walled carbon nanotubes (SWNTs) were prepared by grafting PEI with one of three molecular weights (1.8, 10 and 25 kDa) through succinate as a linker which refers to "an organic moiety through which a SWNT is conjugated to PEI." The succinate linker was introduced to the surface of SWNTs through two different chemical strategies: a) ester and b) acyl linkages. The resulting SWNT-PEI vectors were characterized by IR spectroscopy, thermogravimetric analysis (TGA) and SEM imaging. All synthesized carriers were evaluated and compared for their cytotoxicity and transfection efficiency in murine neuroblastoma cells as polyplexes with plasmid DNA for luciferase and green fluorescent protein (GFP). The most efficient carriers were prepared by attaching PEI with the lowest molecular weight (1.8 kDa) through acyl linkage, which gave a transfection efficiency 190-fold greater than that of the corresponding free PEI. Transfection efficiency was the highest in polyplexes prepared with acyl-linked conjugates in all the plasmid/vector ratios studied.

(Invited) Interfacial Engineering of Two-Dimensional Nanomaterials: Chemical Functionalization and Scanning Probe Characterization

Atomically thin two-dimensional (2D) materials have recently emerged as promising materials for electronic and photonic devices due to their unique layer-number-dependent properties. Because they are atomically thin, interfacial interactions between 2D materials and their surroundings play an important role in regulating their properties for device applications. The electronic and optical properties of 2D materials can be readily engineered by covalent and non-covalent chemical functionalization methods, and can be characterized with atomic-scale precision using scanning probe microscopies. In this work, we demonstrate the functionalization of MoS2 and WSe2 by covalent and non-covalent chemistries, which result in charge transfer, layer-dependent reactivities, and molecular rearrangements at their surfaces. We characterize the structural, electronic, and optical changes to the 2D materials using ultrahigh vacuum scanning tunneling microscopy (UHV STM), atomic force microscopy (AFM), and Raman and photoluminscence (PL) spectroscopic mapping. By controlling the chemical groups that are used in the functionalization reactions, we can engineer their effect on the interfacial properties of 2D materials, which will be important to the processing of novel electronic and photonic devices.

Preparation and characterization of trihydroxamic acid functionalized carbon materials for the removal of Cu(II) ions from aqueous solution

The main objective of this study is to prepare and characterize two functionalizated carbon materials with enhanced adsorptive properties for Cu(II). Thus, two novel hybrid materials have been prepared by a non-covalent functionalization method based on the adsorption of a pyrimidine-desferrioxamine-B conjugate compound (H4L) on two activated carbons, ACs (labelled Merck and F). The adsorption of H4L on the ACs is pH-dependent and highly irreversible. This is due to strong π-π interactions between the arene centers of the ACs and the pyrimidine moiety of H4L. The textural characterization of the AC/H4L hybrids shows large decreases of their surface areas. Thus the values of Merck and F are 1031 and 1426m2/g respectively, while these of Merck/H4L and F/H4L hybrids are 200 and 322m2/g. An important decrease in the micropore volumes is also found, due to the blockage of narrow porosity produced by the adsorption of H4L molecules. The ACs/H4L hybrids show larger adsorption capacities for Cu(II) (0.105(4) and 0.13(2) mmol/g, at pH 2.0, and 0.20(3) and 0.242(9)mmol/g, at pH 5.5, for Merck/H4L and F/H4L, respectively) than those of the ACs (0.024(6) and 0.096(9)mmol/g, at pH 2.0, and 0.10(2) and 0.177(8)mmol/g, at pH 5.5, for Merck and F respectively), which is explained on the basis of the complexing ability of the trihydroxamic acid functions. The desorption of Cu(II) from the ACs/H4L/Cu(II) materials in acid solution allows the regeneration of most active sites (78.5% in the case of Merck/H4L/Cu(II) and 83.0% in the case of F/H4L/Cu(II)).

Crystallization Behavior of Poly(sodium 4-styrenesulfonate)-Functionalized Carbon Nanotubes Filled Poly(ε-caprolactone) Nanocomposites

Multiwalled carbon nanotubes (MWCNTs) were modified with a noncovalent functionalization method via ultrasonication in the presence of poly(sodium 4-styrenesulfonate) (PSS) as a modifier. The PSS-functionalized MWCNTs dispersed well in PCL matrix and showed good interfacial adhesion with PCL after being incorporated by solution coagulation. The isothermal crystallization kinetics of neat PCL and PCL/MWCNT nanocomposites were comparatively investigated by DSC. It was found that the overall crystallization rate of PCL was enhanced significantly, while the crystallization mechanism was unchanged by incorporation of the functionalized MWCNTs. The addition of only 0.1 wt % MWCNT caused 23.4 times improvement in overall crystallization rates, ascribing to the efficient nucleating effect of well-dispersed PSS-functionalized MWCNTs toward crystallization of PCL in the nanocomposites. The spherulitic morphology observation by polarizing optical microscope confirmed the nucleating effect. X-ray diffraction investig...

Enhanced capacitance of a nitrogen-containing carbon-based nanocomposite via noncovalent functionalization method

Ordered carbon (OC) with large surface area was prepared via replication by using Santa Barbara Amorphous-15 as a template and sucrose as a carbon precursor. The prepared OC was then noncovalently functionalized with Basic Red 2 dye precursor (BR2) to obtain OC–BR2, a nitrogen-containing carbon-based nanocomposite with enhanced electrical properties. The functionalization was explained through adsorption isotherm, kinetic, and thermodynamic studies performed under variable conditions. The electrochemical performance test results demonstrated that the nanocomposite presents enhanced capacitance (48.4%) compared with the original OC, with maximum specific capacitance of 227Fg−1 at 0.5Ag−1 in 1M KOH electrolyte.

Direct noncovalent conjugation of folic acid on reduced graphene oxide as anticancer drug carrier

Conjugate of reduced graphene oxide with folic acid (rGO/FA) was prepared through a completely noncovalent functionalization method. rGO/FA conjugate was soluble in physiological media with high dispersion stability and enabled the accumulation of hydrophobic doxorubicin (DOX) and CdSe quantum dot (QD) as an anticancer drug and a fluorescent tag, respectively. rGO/FA conjugate loaded with DOX showed specific targeting to MDA-MB 231 cells, excellent drug-release efficiency and cytotoxicity in vitro. Considering the simplicity and extendibility of noncovalent functionalization methods, rGO/FA conjugate can be widely utilized for the designing of new graphene-based nanocarriers.

埃洛石纳米管增强聚合物复合材料研究进展

Halloysite nanotubes (HNTs) are naturally occurring inorganic nanotubes, which have similar chemical constitution with Kaolinite. Due to their abundance and low cost, combined with superiorelastic modulus and high aspect ratio, HNTs have been widely employed to reinforce and toughen polymer materials. In this review, we briefly summarize the structural characteristics and surface chemical properties of HNTs. Moreover, to improve HNTs dispersion and increase the interfacial interaction between HNTs and polymers, covalent or non-covalent surface functionalization methods for HNTs are utilized. Most importantly, the research progressin the past decade on HNTs reinforced polymer materials which includethermosetting resins, polyamides, polyolefins and rubbers are carefully shown and discussed in detail. Finally, the scientific trends of HNTs/Polymer nanocomposites are proposed.

Electrically conducting polyolefin composites containing electric field-aligned multiwall carbon nanotube structures: The effects of process parameters and filler loading

The characteristics of network formation of multiwall carbon nanotubes (MWCNTs) inside ethylene–octene copolymer (EOC) melts under an alternating current (AC) electric field and the resulting electrical conductivity improvements are studied by combining dynamic and steady state resistivity measurements. Fine MWCNT dispersion during melt compounding of the samples is accomplished by means of a novel non-specific, non-covalent functionalization method. It is found that the electrified composite films exhibit nanotube assembly into columnar structures parallel to the electric field, accompanied by dramatic increases in electrical conductivity up to eight orders of magnitude. Experimentally acquired resistivity data are used to derive correlations between the characteristic insulator-to-conductor transition times of the composites and process parameters, such as electric field strength (E), polymer viscosity (η) and nanotube volume fraction (ϕ). Finally, a criterion for the selection of (η,E,C) conditions that enable MWCNT assembly under an electric field controlled regime (i.e., minimal Brownian motion-driven aggregation effects) is developed. The correlations presented herein not only provide insights in the MWCNT assembly process, but can also guide the experimental design in future studies on electrified composites or assist in the selection of process parameters in composites manufacturing.

Non-covalently functionalized single walled carbon nanotube/poly(3,4ethylenedioxythiophene):poly(styrenesulfonate) nanocomposites for organic photovoltaic cell

In this study, we developed a non-covalent functionalization method to disperse single walled CNTs (SWNTs) with minimal loss of electrical properties. SWNTs were non-covalently functionalized by 1-aminopyrene (AP-SWNTs), and covalently functionalized SWNTs (carboxylate-SWNTs) were fabricated by strong acid treatment for comparing the properties of functionalized SWNTs. By using functionalized SWNTs, SWNT/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) nanocomposites were fabricated as transparent conductive films. AP-SWNT/PEDOT:PSS nanocomposites showed higher electrical conductivity (sheet resistance: 634Ω/sq) at a similar optical transmittance compared to raw PEDOT:PSS (1555Ω/sq) and carboxylate SWNT/PEDOT:PSS nanocomposites (933Ω/sq) due to homogeneously dispersed AP-SWNTs in matrix with minimal damages during the functionalization. We also applied the AP-SWNT/PEDOT:PSS nanocomposites as a hole conducting layer in an organic photovoltaic cell (OPVC) application. Power conversion efficiency (PCE) of the OPVC using AP-SWNT/PEDOT:PSS was enhanced from 2.3% to 3.0% compared to an OPVC using raw PEDOT:PSS. The main reason for this enhancement of the PCE was thought to be the increase of JSC due to effective hole transport and collection by highly conductive, AP-SWNT/PEDOT:PSS nanocomposites.

The effect of non-covalent functionalization on the thermal conductance of graphene/organic interfaces

The intrinsic interfacial thermal resistance at graphene/organic interfaces, as a result of mismatches in the phonon vibrational spectra of the two materials, diminishes the overall heat transfer performance of graphene/organic nanocomposites. In this paper, we use molecular dynamics (MD) simulations to design alkyl-pyrene molecules that can non-covalently functionalize graphene surfaces in contact with a model organic phase composed of octane. The alkyl-pyrene molecules possess phonon-spectra features of both graphene and octane and, therefore, can serve as phonon-spectra linkers to bridge the vibrational mismatch at the graphene/octane interface. In support of this hypothesis, we find that the best linker candidate can enhance the out-of-plane graphene/organic interfacial thermal conductance by ∼22%, attributed to its capability to compensate the low-frequency phonon mode of graphene. We also find that the length of the alkyl chain indirectly affects the interfacial thermal conductance through different orientations of these chains because they dictate the contribution of the out-of-plane high-frequency carbon–hydrogen bond vibrations to the overall phonon transport. This study advances our understanding of the less destructive non-covalent functionalization method and design principles of suitable linker molecules to enhance the thermal performance of graphene/organic nanocomposites while retaining the intrinsic chemical, thermal, and mechanical properties of pristine graphene.

Synthesis and photoluminescence properties of polybenzoxazoles containing perylenebisimide functionalized graphene nanosheets via stacking interactions

The stable acidic dispersion of reduced graphene oxide (RGO) is prepared by a non-covalent functionalization method using perylenebisimide-modified fluorinated poly(hydroxyamide) (PTCDA-6FPHA). Then a series of RGO–polybenzoxazole (PBO) composites were prepared by a solution blending method in MSA. The change of perylenebisimide absorption peaks in the UV-Vis absorption spectra indicates that π–π stacking indeed occurs between graphene and perylene rings. The conjugation between functionalized RGO and PBO molecular chains increases the conjugation degree of the composite, since the PTCDA-6FPHA-containing perylene rings have a high π-electron delocalization degree. The energy gap of RGO–PBO composite is 2.72 eV with the absorption edge at 456 nm. The corresponding data of pure PBO film are 2.78 eV and 446 nm, respectively. Moreover, the intensity of the two emission peaks at 442 and 467 nm in the PL emission spectra of RGO–PBO decreases rapidly along with the increase of RGO–PBO ratio. The intensity of the weak emission peak at 622 nm increases with the increase of the RGO–PBO ratio. This behavior can be attributed to the energy transfer between benzoxazole chromophore units and functionalized RGO. Meanwhile, the RGO–PBO composite has outstanding thermal stability.