End-functionalized polymers by controlled/living radical polymerizations: synthesis and applications

This review focuses on end-functionalized polymers synthesized by controlled/living radical polymerizations and the applications in fields including bioconjugate formation, surface modification, topology construction, and self-assembly.

Functionalization of carbon nanotubes by combination of controlled radical polymerization and "grafting to" method

This paper reviews the recent advances in non-covalent and covalent tethering of small molecules and polymer chains onto carbon nanotube (CNT) and its derivatives. The functionalized CNT has recently attracted great attention because of an increasing number of its potential applications. In non-covalent functionalization of CNT, the sp²-hybridized network plays a crucial role. The non-covalent grafting of small molecules and polymers can mainly be carried out through hydrogen bonding and π-stacking interactions. In covalent functionalization of CNT, condensation, cycloaddition, and addition reactions play a key role. Polymer modification has been reported by using three main methods of "grafting from", "grafting through", and also "grafting to". The "grafting from" and "grafting through" rely on propagation of polymer chains in the presence of CNT modified with initiator and double bond moieties, respectively. In "grafting to" method, which is the main aim of this review, the pre-fabricated polymer chains are mainly grafted onto the surface using coupling reactions. The coupling reactions are used for grafting pre-fabricated polymer chains and also small molecules onto CNT. Recent studies on grafting polymer chains onto CNT via "grafting to" method have focused on the pre-fabricated polymer chains by conventional and controlled radical polymerization (CRP) methods. CRP includes reversible activation, atom transfer, degenerative (exchange) chain transfer, and reversible chain transfer mechanisms, and could result in polymer-grafted CNT with narrow polydispersity index of the grafted polymer chains. Based on the mentioned mechanisms, nitroxide-mediated polymerization, atom transfer radical polymerization, and reversible addition-fragmentation chain transfer are known as the three commonly used CRP methods. Such polymer-modified CNT has lots of applications in batteries, biomedical fields, sensors, filtration, solar cells, etc.

Reactive block copolymers for patterned surface immobilization with sub-30 nm spacing

Reactive polystyrene-block-polyisoprene copolymers are synthesized by nitroxide-mediated polymerization, self-assemble within ultra-thin films, and exhibit surface reactivity for patterned immobilization.

Aqueous Solution Processing of Combustible Precursor Compounds into Amorphous Indium Gallium Zinc Oxide (IGZO) Semiconductors for Thin Film Transistor Applications

Combustion synthesis of semiconducting amorphous indium gallium zinc oxide IGZO (In:Ga:Zn, 7:1:1.5) thin films was carried out using urea nitrate precursor compounds of indium(III), gallium(III) and zinc(II). This approach provides further understanding towards the oxide formation process under a moderate temperature regime by employment of well-defined coordination compounds. All precursor compounds were fully characterized by spectroscopic techniques as well as by single crystal structure analysis. Their intrinsic thermal decomposition was studied by a combination of differential scanning calorimetry (DSC) and thermogravimetry coupled with mass spectrometry and infrared spectroscopy (TG-MS/IR). For all precursors a multistep decomposition involving a complex redox-reaction pathway under in situ formation of nitrogen containing molecular species was observed. Controlled thermal conversion of a mixture of the indium, gallium and zinc urea nitrate complexes into ternary amorphous IGZO films could thus be achieved. Thin film transistors (TFTs) were fabricated from a defined compositional mixture of the molecular precursors. The TFT devices exhibited decent charge carrier mobilities of 0.4 and 3.1 cm² /(Vs) after annealing of the deposited films at temperatures as low as 250 and 350 °C, respectively. This approach represents a significant step further towards a low temperature solution processing of semiconducting thin films.

Controllable Multinary Alloy Electrodeposition for Thin-Film Solar Cell Fabrication: A Case Study of Kesterite Cu2ZnSnS4

Electrodeposition (ED) technology is a low-cost industrial candidate for solar cell fabrication. However, the practical aspects of controlling deposit morphology and composition have not been significantly addressed because of the complex co-plating variables that still need to be understood for multinary alloy ED. This work addresses these practical aspects on how to control composition and deposit morphology using co-electrodeposited kesterite alloy precursors as a case study. The alloy precursors co-plated under the optimized conditions from a mixed thiosulfate-sulfite electrolyte bath show uniform, smooth, and compact film morphology as well as uniform distribution of composition, well suited for efficient kesterite absorbers, finally delivering a Cu₂ZnSnS₄ (CZTS) thin-film solar cell with 7.4% efficiency based on a configuration Mo/CZTS/CdS/ZnO/aluminum-doped ZnO. This work underscores that alloy ED, with the advantage of controllable composition and morphology, holds promise for low-cost industrial manufacture of thin-film solar cells.

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Simultaneous control of the composition and morphology of the alloy electrodeposit

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Alloy electrodeposits with superb uniformity in film appearances and compositions

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The best kesterite Cu₂ZnSnS₄ mini solar cell with a 7.4% power conversion efficiency

Ultrasound-promoted direct functionalization of multi-walled carbon nanotubes in water via Diels-Alder "click chemistry"

A facile and environmentally friendly strategy for grafting polymers onto the surface of multi-walled carbon nanotubes (CNTs) was demonstrated by Diels-Alder "click chemistry". Firstly, the copolymers of poly(styrene-alt-maleic anhydride) (PSM) were prepared by the reversible addition-fragmentation chain transfer (RAFT) polymerization and subsequently functionalized with furfuryl amine to introduce anchoring groups. The copolymers were then grafted on CNTs via the Diels-Alder reaction in water through a conventional heating-stirring route and ultrasound-assisted method. The obtained nanocomposite materials were characterized by thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. The results indicated that the reaction rate under ultrasound irradiation was accelerated about 12 times than the one under the conventional heating-stirring condition without losing the grafting efficiency. The direct functionalization of CNTs formed a stably dispersed solution in water, promising a green and effective method for industrial process.

Organic solar cells with graded absorber layers processed from nanoparticle dispersions

The fabrication of organic solar cells with advanced multi-layer architectures from solution is often limited by the choice of solvents since most organic semiconductors dissolve in the same aromatic agents. In this work, we investigate multi-pass deposition of organic semiconductors from eco-friendly ethanol dispersion. Once applied, the nanoparticles are insoluble in the deposition agent, allowing for the application of further nanoparticulate layers and hence for building poly(3-hexylthiophene-2,5-diyl):indene-C60 bisadduct absorber layers with vertically graded polymer and conversely graded fullerene concentration. Upon thermal annealing, we observe some degrees of polymer/fullerene interdiffusion by means of X-ray photoelectron spectroscopy and Kelvin probe force microscopy. Replacing the common bulk-heterojunction by such a graded photo-active layer yields an enhanced fill factor of the solar cell due to an improved charge carrier extraction, and consequently an overall power conversion efficiency beyond 4%. Wet processing of such advanced device architectures paves the way for a versatile, eco-friendly and industrially feasible future fabrication of organic solar cells with advanced multi-layer architectures.

Recent advances in organic–inorganic well-defined hybrid polymers using controlled living radical polymerization techniques

Controlled living radical polymerizations, such as ATRP and RAFT polymerization, could be utilized for the preparation of well-defined organic–inorganic hybrid polymers based on POSS, PDMS, silica nanoparticles, graphene, CNTs and fullerene.

Adsorption of pure SO2 on nanoscaled graphene oxide

Carbon materials are widely used for adsorptive removal of corrosive or green-house gases like SO₂ or CO₂. Graphene oxide is accessible in bulk quantities and thus may represent a viable replacement for other nanostructured carbon materials.

Surface modification of carbon nanotubes by combination of mussel inspired chemistry and SET-LRP

Surface modification of carbon nanotubes by the combination of mussel inspired chemistry and SET-LRP has been reported for the first time.

π-conjugated polymer-fullerene covalent hybrids via ambient conditions Diels-Alder ligation

The established ability of graphitic carbon-nanomaterials to undergo ambient condition Diels-Alder reactions with cyclopentadienyl (Cp) groups is herein employed to prepare fullerene-polythiophene covalent hybrids with improved electron transfer and film forming characteristics. A novel precisely designed polythiophene (M n 9.8 kD, Đ 1.4) with 17 mol% of Cp-groups bearing repeat unit is prepared via Grignard metathesis polymerization. The UV/Vis absorption and fluorescence (λex 450 nm) characteristics of polythiophene with pendant Cp-groups (λmax 447 nm, λe-max 576 nm) are comparable to the reference poly(3-hexylthiophene) (λmax 450 nm, λe-max 576 nm). The novel polythiophene with pendant Cp-groups is capable of producing solvent-stable free-standing polythiophene films, and non-solvent assisted self-assemblies resulting in solvent-stable nanoporous-microstructures. (1) H-NMR spectroscopy reveals an efficient reaction of the pendant Cp-groups with C60 . The UV/Vis spectroscopic analyses of solution and thin films of the covalent and physical hybrids disclose closer donor-acceptor packing in the case of covalent hybrids. AFM images evidence that the covalent hybrids form smooth films with finer lamellar-organization. The effect is particularly remarkable in the case of poorly soluble C60 . A significant enhancement in photo-voltage is observed for all devices constituted of covalent hybrids, highlighting novel avenues to developing efficient electron donor-acceptor combinations for light harvesting systems.