Optimum degree of functionalization for carbon nanotubes

Shiren Wang 한국물리학회 2009 Current Applied Physics Vol.9 No.5

Covalent functionalizations, especially oxidization and derivative functionalization, significantly improve the surface characteristics of carbon nanotubes, but also bring undesired devastation of sidewalls. This paper presents a theoretic model to investigate double-edge effects of covalent functionalization on carbon nanotubes for the polymer composite application. An optimal degree of functionalization is proposed and calculated based on the trade-off of required load-transfer and induced devastation of nanotube sidewalls The negative effect on elastic modulus is also calculated. For oxidization-based functionalization of originally defect-free nanotubes, the calculation results indicate that about 10% functionalization degree is suggested to be optimum for the balance of efficient load-transfer and conspicuous devastation from the highly covalent functionalization. The original defects in nanotube surface also reduce the optimum functionalization degree and the reduction is dependent on the original defect concentration. The computational results indicate that nanotube diameter and percentages in the polymer composites show considerably effect on the optimum functionalization degree. Carbon nanotubes with smaller diameter show lower optimum functionalization degree. Increasing percentage of carbon nanotubes in the polymer composites also leads to lower optimum functionalization degree.

Tandem annulation and dipolar cycloaddition of azomethine imines in catalytic C(sp 2 )–H functionalization

Mishra Neeraj Kumar,Rakshit Amitava,문경원,Singh Pargat,김인수 대한화학회 2024 Bulletin of the Korean Chemical Society Vol.45 No.2

The synthesis and functionalization of privileged nitrogen heterocycles has emerged as a central topic in drug discovery and material science. In this context, the tandem C–H functionalization and intramolecular annulation has received prodigious attention, as it is able to expedite the construction of heteroaromatic frameworks beyond conventional C–H functionalization. In general, significant effort has been made to develop the [3 + 2] dipolar cycloaddition of azomethine imines with π‐unsaturated compounds. Moreover, the [3 + 3], [4 + 3], [3 + 2 + 2], and [5 + 3] cycloaddition reactions of azomethine imines with various dipolarophiles have been demonstrated. To date, however, the combination of catalytic C–H functionalization and intramolecular cyclization using azomethine imines as both directing groups and dipolar units has been less explored. This review focuses on recent progress toward the catalytic tandem C–H functionalization and dipolar cycloaddition of azomethines imines with a range of coupling partners. The synthesis and functionalization of privileged nitrogen heterocycles has emerged as a central topic in drug discovery and material science. In this context, the tandem C–H functionalization and intramolecular annulation has received prodigious attention, as it is able to expedite the construction of heteroaromatic frameworks beyond conventional C–H functionalization. In general, significant effort has been made to develop the [3 + 2] dipolar cycloaddition of azomethine imines with π-unsaturated compounds. Moreover, the [3 + 3], [4 + 3], [3 + 2 + 2], and [5 + 3] cycloaddition reactions of azomethine imines with various dipolarophiles have been demonstrated. To date, however, the combination of catalytic C–H functionalization and intramolecular cyclization using azomethine imines as both directing groups and dipolar units has been less explored. This review focuses on recent progress toward the catalytic tandem C–H functionalization and dipolar cycloaddition of azomethines imines with a range of coupling partners.

Plasma functionalization of powdery nanomaterials using porous filter electrode and sample circulation

Lee, Deuk Yeon,Choi, Jae Hong,Shin, Jung Chul,Jung, Man Ki,Song, Seok Kyun,Suh, Jung Ki,Lee, Chang Young Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.443 No.-

<P><B>Abstract</B></P> <P>Compared with wet processes, dry functionalization using plasma is fast, scalable, solvent-free, and thus presents a promising approach for grafting functional groups to powdery nanomaterials. Previous approaches, however, had difficulties in maintaining an intimate sample-plasma contact and achieving uniform functionalization. Here, we demonstrate a plasma reactor equipped with a porous filter electrode that increases both homogeneity and degree of functionalization by capturing and circulating powdery carbon nanotubes (CNTs) via vacuum and gas blowing. Spectroscopic measurements verify that treatment with O<SUB>2</SUB>/air plasma generates oxygen-containing groups on the surface of CNTs, with the degree of functionalization readily controlled by varying the circulation number. Gas sensors fabricated using the plasma-treated CNTs confirm alteration of molecular adsorption on the surface of CNTs. A sequential treatment with NH<SUB>3</SUB> plasma following the oxidation pre-treatment results in the functionalization with nitrogen species of up to 3.2 wt%. Our approach requiring no organic solvents not only is cost-effective and environmentally friendly, but also serves as a versatile tool that applies to other powdery micro or nanoscale materials for controlled modification of their surfaces.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Our plasma reactor enables uniform functionalization of powdery nanomaterials. </LI> <LI> The reactor is equipped with a porous filter electrode and a gas-blower. </LI> <LI> The porous electrode captures powdery materials and functionalizes them by plasma. </LI> <LI> The sample can be repeatedly circulated via vacuum-filtration and gas-blowing. </LI> <LI> Sample circulation increases the degree and the homogeneity of functionalization. </LI> </UL> </P>

Review on Functionalization of Laser-Induced Graphene

안진우,김희재,이승기 한국전기전자재료학회 2023 전기전자재료학회논문지 Vol.36 No.3

Owing to carbon materials’ diverse functionalization and versatility, the design and synthesis of carbon-based threedimensionalporous structures have become important foundational research topics across various fields. Among the variousmethods for producing porous carbon structures, laser-induced graphene (LIG) has garnered attention because of its large surfacearea, controllable structure, excellent electrical conductivity, scalability, and eco-friendly synthesis process. In addition, recentresearch results have reported more novel functionalities by advancing further from the unique characteristics of LIG through functionalization or compounding of LIG, making it an attractive material for various applications in electronic devices, sensing, catalysis, and energy storage. This review aims to update the research trends in LIG and its functionalization, providing insights to inspire more interesting studies on functional LIG to expand its potential applications ultimately. Starting with the synthesis method and material characteristics of LIG, we introduce the functionalization of LIG, which is classified into surface modification, heteroatom doping, and hybridization based on the interaction mechanism. Finally, we summarize and discuss the prospects of LIG and its functionalization.

Thiol-based chemistry as versatile routes for the effective functionalization of cellulose nanofibers

An, Sol,Jeon, Bokyoung,Bae, Jong Hyuk,Kim, Ick Soo,Paeng, Keewook,Kim, Myungwoong,Lee, Hoik Elsevier 2019 Carbohydrate Polymers Vol.226 No.-

<P><B>Abstract</B></P> <P>We demonstrate effective functionalization chemistry for cellulose nanofiber modification using thiol functionality. Electrospun cellulose acetate nanofibers were deacetylated to obtain cellulose nanofibers, which were modified further to incorporate thiol on their surface by the esterification of hydroxyl groups with 3,3′-dithiodipropionic acid and further reductive cleavage of the disulfide bond. The thiol functionality was highly versatile to bring simple and efficient chemical reactions to attain (i) Ag nanoparticle-adsorbed cellulose nanofibers by Ag ion reduction at surface, (ii) various amine (primary amine and quaternary amine) functionalized cellulose nanofibers by Michael addition, and (iii) complex polymer functionalized cellulose nanofibers by a radical-based thiol-ene reaction, under mild conditions, i.e. in any reaction media, at room temperature, and under ambient atmosphere, evidenced by a variety of characterization methods including a quantitative analysis with X-ray photoemission spectroscopy. These scalable thiol-based chemistries should offer a new generation of well-tailored cellulose nanofiber materials with complex inorganic, organic, and polymeric functionalities, potentially expanding to functionalized surfaces of other carbohydrate-based materials to achieve the desired properties.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Simple, easy, versatile, efficient, scalable thiol-based chemistry for cellulose functionalization. </LI> <LI> Resourcefulness of thiol: metal adsorption, radical stability, and strong nucleophilicity. </LI> <LI> Functionalization of inorganic particles, complex functional molecules and polymers. </LI> <LI> Expandability for functionalization of carbohydrate-based materials achieving desired properties. </LI> </UL> </P>

The effect of surface functionalization of PLGA nanoparticles by heparin- or chitosan-conjugated Pluronic on tumor targeting

Chung, Y.I.,Kim, J.C.,Kim, Y.H.,Tae, G.,Lee, S.Y.,Kim, K.,Kwon, I.C. Elsevier Science Publishers 2010 Journal of controlled release Vol.143 No.3

The poly (lactide-co-glycolide) (PLGA)-based nanoparticles, coated by the heparin- or chitosan-Pluronic conjugate, were used to improve a relatively low tumor-targeting efficiency of the bare PLGA nanoparticles. The prepared nanoparticles were in the size range of 100-150nm, and the surface exposure of the functional moiety (heparin or chitosan) was confirmed by negatively or positively increased zeta potential values, respectively. The viability tests for both normal and tumor cells displayed minimal cytotoxicity of the nanoparticles. The stable surface coating, which was evident from no change in the size distribution profiles in spite of the surface charge changes in serum environment, effectively provided the desired functionalized surface that clearly enhanced the in vitro cellular uptake of the nanoparticles for both heparin and chitosan functionalization. The in vivo tumor model study, which was carried out in SCC7 tumor-bearing athymic mice, demonstrated that there was a limited, but positive effect of surface functionalization, more effective for chitosan functionalization. The accumulation of chitosan-functionalized PLGA nanoparticles in tumor was 2.4 folds higher than that of the control, PLGA nanoparticles coated with bare Pluronic, and the accumulation in liver was lower than the control. In the case of heparin functionalization, the mean value was 2.2 folds higher than that of the control, but the accumulation in liver was similar to that of the control. Therefore, the surface-functionalization by the chitosan- or heparin-conjugated Pluronic may be an effective approach for the hydrophobic nanoparticle systems aiming for the enhanced tumor imaging and therapy.

다중벽 탄소나노튜브의 표면처리 방법에 따른 특성비교

박기룡,김준석,정영진,Park, Gi-Ryoung,Kim, Jun-Suk,Jeong, Young-Jin 한국섬유공학회 2008 한국섬유공학회지 Vol.45 No.6

Functional groups on multi-walled carbon nanotubes (MWNTs) were introduced by UV/ozone treatment, reacting with $HNO_3$ alone or with $H_2SO_4/HNO_3$ mixture followed by drying under different conditions. The resulting MWNTs were characterized using a UV-visible spectrometer, SEM, FT-IR, elemental analyzer, and TGA. The amount of oxygen was measured with elemental analyzer and used to check the degree of functionalization on the MWNT surface. Among the various methods tested, the one using $H_2SO_4/HNO_3$ introduced highest amount of carboxyl groups on the carbon nanotubes, while it damaged the MWNTs. Also, even with the similar amount of functional groups, dispersibility of the functionalized MWNTs in water was differed according to the functionalization method. The carbon nanotubes functionalized by reacting with $H_2SO_4/HNO_3$ started to degrade at lower temperature than the ones treated by other methods, which was due to the defects introduced during functionalization.

실리카의 이온성 액체 기능화가 메탈로센 담지촉매의 에틸렌 중합 거동에 미치는 영향

이정숙 ( Jeong Suk Lee ),이창일 ( Chang Il Lee ),고영수 ( Young Soo Ko ) 한국공업화학회 2016 공업화학 Vol.27 No.1

Three amorphous silicas and SBA-15 were employed as supports, which were capable of confining ionic liquid (IL) and metallocene in the nanopore. Ionic liquid functionalized silica was prepared by the interaction between the chloride anions of 1,3-bis(cyanomethyl) imidazolium chloride and the surface OH groups. Metallocene and methylaluminoxane (MAO) were subsequently immobilized on the ionic liquid functionalized silica for ethylene polymerization. The metallocene supported on ionic liquid functionalized XPO-2412 and XPO-2410 having a larger pore diameter compared to SBA-15 showed higher activity than that of using supported catalyst without ionic liquid functionalization. However, the activity of metallocene supported on SBA-15 decreased after ionic liquid functionalization, suggesting that the diffusion of ethylene monomer and cocatalyst to the active site of nanopore was restricted during ethylene polymerization. This could be resulted from significant reduction of the pore diameter due to the immobilization of ionic liquid and (n-BuCp)2ZrCl2 and MAO. The effect on polymerization activity in accordance with the concentration of hydroxyl groups on the surface was also investigated. The polymerization activity increased as the concentration of hydroxyl groups on amorphous silica increased. The polymerization activities of metallocene supported on silica showed the similar trend after ionic liquid functionalization.

Tuning the Photoluminescence of Graphene Quantum Dots through the Charge Transfer Effect of Functional Groups

Jin, Sung Hwan,Kim, Da Hye,Jun, Gwang Hoon,Hong, Soon Hyung,Jeon, Seokwoo American Chemical Society 2013 ACS NANO Vol.7 No.2

<P>The band gap properties of graphene quantum dots (GQDs) arise from quantum confinement effects and differ from those in semimetallic graphene sheets. Tailoring the size of the band gap and understanding the band gap tuning mechanism are essential for the applications of GQDs in opto-electronics. In this study, we observe that the photoluminescence (PL) of the GQDs shifts due to charge transfers between functional groups and GQDs. GQDs that are functionalized with amine groups and are 1–3 layers thick and less than 5 nm in diameter were successfully fabricated using a two-step cutting process from graphene oxides (GOs). The functionalized GQDs exhibit a redshift of PL emission (<I>ca</I>. 30 nm) compared to the unfunctionalized GQDs. Furthermore, the PL emissions of the GQDs and the amine-functionalized GQDs were also shifted by changes in the pH due to the protonation or deprotonation of the functional groups. The PL shifts resulted from charge transfers between the functional groups and GQDs, which can tune the band gap of the GQDs. Calculations from density functional theory (DFT) are in good agreement with our proposed mechanism for band gap tuning in the GQDs through the use of functionalization.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-2/nn304675g/production/images/medium/nn-2012-04675g_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn304675g'>ACS Electronic Supporting Info</A></P>

Fabrication of pore-selective carboxyl group functionalized polyimide honeycomb-patterned porous films using KOH humidity

Cao, Thuy Thi,Male, Umashankar,Huh, Do Sung Elsevier 2018 Polymer Vol.153 No.-

<P><B>Abstract</B></P> <P>Carboxyl group functionalization in honeycomb-patterned porous (HCP) films was obtained by breath figure process using polyimide (PI) which can react with KOH humidity at the polymer solution/aqueous alkali droplet interface to form carboxyl groups. PI containing CO-NR<SUB>2</SUB> imide ring group reacts with KOH for imide ring-cleavage reaction by interfacial reaction. In order to obtain pore-selective carboxyl group functionalized PI HCP films, we have suggested a new strategy introducing KOH humidity with time interval after using initial water humidity during breath figuring process. The carboxyl group functionalized pores can be applied to obtain ordered microarray of biological and inorganic materials, which have potential applications in biosensors, separations, medical biology, etc.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new strategy was developed for the pore selective carboxyl functionalization. </LI> <LI> Polyimide reacts with KOH humidity to form carboxyl functionalized porous films. </LI> <LI> Pore functionalization was enhanced by delayed introduction of KOH humidity. </LI> <LI> Reactive carboxyl pores can be used as a template for further functionalization. </LI> <LI> Silver functionalized porous polyimide films by ion-exchange self-metallization. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>