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Enhanced Dispersibility of Graphitic Carbon Nitride Particles in Aqueous and Organic Media Via a One Pot Grafting Approach

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Enhanced Dispersibility of Graphitic Carbon Nitride Particles in Aqueous and Organic Media Via a One Pot Grafting Approach View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by MPG.PuRe MPIKG Public Access Author Manuscript Published in final edited form as: Kumru, B., Antonietti, M., & Schmidt, B. V. K. J. (2017). Enhanced Dispersibility of Graphitic Carbon Nitride Particles in Aqueous and Organic Media via a One Pot Grafting Approach. Langmuir, 33(38), 9897-9906. doi:10.1021/acs.langmuir.7b02441. Enhanced Dispersibility of Graphitic Carbon Nitride Particles in Aqueous and Organic Media via a One Pot Grafting Approach Baris Kumru, Markus Antonietti, Bernhard V.K.J. Schmidt ipt Enhanced Dispersibility of Graphitic Carbon Nitride Manuscr · Author · Particles in Aqueous and Organic Media via a One Pot Grafting Approach Baris Kumru, Markus Antonietti, Bernhard V.K.J. Schmidt* Department of Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, Research Campus Golm, 14424 Potsdam (Germany) Max Planck Institute of Colloids and Interfaces Interfaces and Colloids of Institute MaxPlanck KEYWORDS Carbon Nitride, Dispersibility, Grafting ABSTRACT A facile route to synthesize hydrophilically or hydrophobically grafted graphitic carbon nitride (g1CN) is reported. 3or this purpose, functionali0ed olefinic olecules with low poly eri0ation tendency are utili0ed for grafting onto the surface in order to preserve the features of g1CN while i proving its dispersibility. One pot, visible light induced grafting yields highly dispersible g1CNs either in aqueous or organic edia. Moreover, functional groups such as a ine can be introduced, which yields p5 dependent dispersibility in aqueous edia. Co pared with unfunctionali0ed g1CN low sonication ti es are sufficient to redisperse g1CN. In addition, due to increased dispersion stability, higher a ounts of functionali0ed g1CN can be dispersed (up to 107 in aqueous dispersion and 27 in organic dispersion), when co pared to unfunctionali0ed g1CN. 2 Introduction ipt Graphitic carbon nitride (g1CN) is a etal1free photocatalytic aterial significantly active in 1,2 Manuscr the visible light range between 8901480 n . It is generally co posed of repeating tri1s1tria0ine rings8 , and its properties can be adjusted by changing the synthesis conditions, such as · Author · poly eri0ation te perature4,5 and utili0ed precursors.6,7 As heterogeneous catalyst, it raised 8 9111 12 interest e.g. in CO2 reduction, water splitting, designed organic reactions, photodegradation18,14 and very recently as an a phiphile and Pickering e ulsion1dispersion stabili0er.15 The high che ical and ther al stability of g1CN as well as convenient synthesis and low cost precursors ake it also a pro ising candidate for any photocatalytic applications.16 Lately, g1CN was investigated as radical initiator in poly eri0ation reactions together with tertiary a ines as co1catalyst.17 Therein, researchers successfully integrated g1CN as radical Max Planck Institute of Colloids and Interfaces Interfaces and Colloids of Institute MaxPlanck initiator in free radical and controlled poly eri0ations of styrene as well as ethyl ethacrylate. Moreover, ,eber et. al. investigated the for ation of poly er1 esoporous g1CN co posites by aerosol poly eri0ation using N1 ethyldiethanola ine as co1catalyst.18 Recently, our group investigated the role of g1CN in the for ation of reinforced hydrogels and photocatalytically active hydrogels without any co1catalyst.19,20 All these experi ents suggested the for ation of radicals on the surface of g1CN, which are capable of initiation of free radical poly eri0ation. Modification of g1CN is relevant when the activity of un odified g1CN is not at the desired level. There are two routes towards odification, either via changing synthesis conditions or post1synthesis odification.21 Changing synthesis conditions such as preorgani0ation of ono ers,22,28 solvent addition24 and poly eri0ation te perature4,25 yields g1CNs with different specific surface area26 and functional groups.27,28 Post synthetic ethods can be considered as protonation of g1CN,29 doping80 and acro olecular grafting.81 3or heterogeneous catalysis 3 syste s, for ation of active centers and their interaction with the solvent are i portant factors ipt for the rate of reaction.82 These odified g1CNs are used in enhanced visible light 88 84 Manuscr photodegradation and roo te perature esterification of fatty acids to yield biodiesels. 5owever, the ain drawback for the utili0ation of g1CN is weak dispersibility since strong van · Author · der ,aals attractions (@1@ stacking) of sp2 carbons cause re1agglo eration in solvents.85 Therefore, the use of dispersed g1CN is li ited, and only li ited a ounts of g1CN can be dispersed in ti e consu ing processes as reaggregation is a colloidal process which is highly concentration dependent. The ain approaches to enhance dispersibility are hydrophilic odification of g1CN86 or utili0ation of additives, such as surfactants or strong acids, during the dispersion step.87 Yet these additives can be undesirable for ai ed reaction conditions and thus decrease the applicability, e.g. surfactants are challenging to re ove after the reaction, strong Max Planck Institute of Colloids and Interfaces Interfaces and Colloids of Institute MaxPlanck acids can interfere with reactants or with the reaction echanis . Recently, ,ang and coworkers reported the odification of g1CN nanosheets with oxygen plas a treat ent in order to introduce hydroxyla ine groups to enhance the degree of protonation.88 The reaction conditions required long ultrasonication ti es to yield nanosheets first and then plas a treat ent under high pressure and icrowave irradiation. Yet, to the best of our knowledge, there are no reports on g1CN dispersion in organic edia or p51dependent g1CN dispersion in aqueous ediu . Inspired by our recent work on CN photoinitiation for hydrogel for ation,19,20 we here atte pt to utili0e radicals on the CN surface for odificationA radicals are created on the surface of g1CN via visible light, and various functionalities are integrated. In order to suppress poly eri0ation, functional non1propagating allyl co pounds were utili0ed as depicted in Sche e 1. 4 ipt Manuscr · Author · Scheme 1. Overview for g1CN modifications based on light induced grafting. IPAA isopropanol. Max Planck Institute of Colloids and Interfaces Interfaces and Colloids of Institute MaxPlanck 3unctionalities such as sulfonic acids, alkane chains, a ino groups and fluoro groups are introduced to g1CN, which was synthesi0ed fro cyanuric acid1 ela ine (CM) co plex and is annotated as CM. 3acile light induced syntheses together with a convenient purification process yield highly dispersible g1CNs. It is shown that g1CNs odified with various functionalities enables quick dispersion ti es and increased solid contents in the respective solvents co pared to non1functionali0ed reference g1CN (up to 10 wt27 in water and 2 wt27 in acetone). Moreover, it is possible to introduce p5 dependent functionalities via grafting of allyla ine. Experimental Section Materials All aterials were used as purchased unless noted otherwise. Acetone (5PLC grade, Sig a Aldrich), allyla ine (987, Sig a Aldrich), 81allyloxy121hydroxy111propanesulfonic acid 5 sodiu salt solution (40 wt27, A5PA, Sig a Aldrich), cyanuric acid (987, Sig a Aldrich), 11 ipt decene (947, Sig a Aldrich), deuterated chlorofor (CDCl8, Sig a Aldrich), deuteriu oxide Manuscr (D2O, Sig a Aldrich), dichloro ethane (DCM, anhydrous 99.87, Sig a Aldrich), hexafluoroben0ene (997, Alfa Aesar), hexane (anhydrous, 957, Sig a Aldrich), hydrochloric · Author · acid (0.1 N, Alfa Aesar), hydrogen peroxide solution (50 wt27, Sig a Aldrich), isopropyl alcohol (IPA, 99.77, Sig a Aldrich), ela ine (997, Sig a Aldrich), 1H,1H,2H1perfluoro111 decene (997, Alfa Aesar), sodiu hydroxide (Sig a Aldrich), tetrahydrofuran (TH3, anhydrous, 99.97, Sig a Aldrich), triethanola ine (997, Sig a Aldrich) and toluene (anhydrous 99.87, Sig a Aldrich). Bisible light irradiation was perfor ed via two 50 , LED chips (3oxpic 5igh Power 50 , LED Chip .ulb Light DIY ,hite 8800LM 6500 K) connected to a self1 ade circuit and cooling syste . CB light irradiation was perfor ed via 5 , LED Max Planck Institute of Colloids and Interfaces Interfaces and Colloids of Institute MaxPlanck stripes (Chili1Tec, CLS1100CB) containing 80 CB SMD LEDs (type 5050, λ D 895 n ). Sonication was perfor ed in a sonication bath fro El a (Transsonic T310). G1CN was synthesi0ed fro cyanuric acid1 ela ine (CM) co plex according to the literature and was annotated as CM.89 Characterization Eeta potential and si0e (by dyna ic light scattering, λ D 688 n at θ D 90F, E1averaged dia eters are presented) easure ents of colloidal suspensions of CMs were perfor ed with a Eetasi0er Nano ES90 fro Malvern. G1ray diffraction (GRD) patterns were obtained using .ruker D8 Advance G1ray diffracto eter via Cu1KH radiation. Scanning electron icroscopy (SEM) was perfor ed using ISM175003 (IEOL) equipped with an Oxford Instru ents G1MAG 80 2 detector for the deter ination of the ele ental co position of CM sa ples. The structures of aterials were also exa ined by TEM using an EM 912 O ega icroscope at 120 6 kB. 3ourier transfor infrared (3T1IR) spectra were acquired on a Nicolet iS 5 3/1IR ipt spectro eter. Solid state ultraviolet1visible (CB1Bis) spectroscopy was recorded via a Cary 500 Manuscr Scan spectrophoto eter equipped with an integrating sphere. Ato ic 3orce Microscopy (A3M) was perfor ed via Digital Instru ents by dispersing sa ples in water and drying on ica. · Author · Ele ental analyses of the sa ples were recorded via a Bario Micro device. Photolu inescence spectra of the sa ples were obtained by a 5itachi 317000 spectro eter. 15 NMR was recorded at a bient te perature at 400 M50 with a .ruker Ascend400. Sedi entation videos were prepared by taking i ages of dispersions continuously with a ca era fro Logitech connected to co puter in custo made set up and transfor ed into a short video. Time dependent synthesis of AHPA grafted CM 50 g CM was weighted in a glass vial with agnetic stirrer, 1 g A5PA solution (40 wt27 in Max Planck Institute of Colloids and Interfaces Interfaces and Colloids of Institute MaxPlanck water) and 1 g deioni0ed water were added.
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