Ying-Ying Zhang

Au nanoparticles on ultrathin MoS2 sheets for plasmonic organic solar cells

A novel hole transport layer (HTL) composed of ultrathin two-dimensional, molybdenum disulfide (MoS2) sheets decorated with 20 nm gold nanoparticles (NPs) (MoS2@Au) was developed to make use of plasmonics for organic solar cells (OSCs). Both experimental and theoretical simulations revealed that the device with the MoS2@Au composite as the HTL exhibited enhanced short-circuit photocurrent density (Jsc) and efficiency compared to that with MoS2 alone as the HTL.

Ultra-stable two-dimensional MoS2 solution for highly efficient organic solar cells

A simple and effective procedure was developed to modify chemically exfoliated MoS2 surfaces with a hydrophilic surfactant through electrostatic interaction. The modified ce-MoS2 colloidal solution shows ultra long-term stability, making it a storable solution ready for highly efficient organic solar cells.

Functional poly(carbonate-co-ether) synthesis from glycidyl methacrylate/CO2 copolymerization catalyzed by Zn–Co(III) double metal cyanide complex catalyst

Polycarbonates with pendant functional groups have attracted much attention due to their capability for further chemical modification and post-polymerization. This work describes the synthesis of a poly(carbonate-co-ether) with massive pendant acrylate groups from the copolymerization of glycidyl methacrylate (GMA) with carbon dioxide (CO2), using a nanolamellar zinc-cobalt double metal cyanide complex (Zn–Co(III) DMCC) catalyst. The carbonate linkage content (FCO2) of the poly(carbonate-co-ether) could be varied from 42.2 to 68.0% by changing the polymerization conditions. Of importance, 4-methoxyphenol was applied for regulating the copolymerization. It could not only act as an inhibitor for completely depressing the self-polymerization of GMA via free radical polymerization of the double bond, but also modulate the molecular weight of the resultant copolymers. The obtained copolymer had two terminal hydroxyl groups, which were confirmed by the electrospray ionization-tandem mass spectrometry (ESI-MS) technique. A new thermoset with high glass transition temperature (Tg: 105 or 120 °C) and massive carbonate units as well as hydroxyl (or carboxylic) groups was prepared by the curing reaction of the GMA–CO2 copolymer with allyl alcohol or acrylic acid in the presence of 2,2′-azobisisobutyronitrile (AIBN).

Synthesis of fully alternating polycarbonate with low Tg from carbon dioxide and bio-based fatty acid

The selective copolymerization of CO2 and an epoxide to form fully alternating polycarbonates is a great challenge via catalysis with the zinc–cobalt(III) double metal cyanide complex [Zn–Co(III) DMCC]. We describe the first perfectly alternating copolymerization of CO2 with a bio-based epoxide. The resultant polycarbonate had a low Tgs of −38 to −44 °C and two end hydroxyl groups, which were then used to initiate ring-opening polymerization of L-lactide via metal-free catalysis, affording a biodegradable triblock copolymer. This study provides a new platform copolymer for making various advanced polymers with biodegradable properties.

Two-dimensional MoS2-assisted immediate aggregation of poly-3-hexylthiophene with high mobility

Nanoscale morphology is of significance to the electronic properties of semiconducting polymers. Solution-processed poly-3-hexylthiophene (P3HT) has been demonstrated as a promising active-layer material in organic thin film transistors (OTFTs) and solar cells. Controlling the crystallinity of P3HT chains is critical for gaining high-performance devices. Here we demonstrated the immediate crystallization of P3HT induced by two-dimensional MoS2 nanosheets under ultrasonication. The resulting aggregation was attributed to the presence of interaction between the MoS2 nanosheets and P3HT, which could enhance the inter-chain ordering and association of P3HT. The crystallization of P3HT contributed to the 38-fold enhancement in the hole mobility of the thin film as compared to the non-crystallized thin films because of the absence of MoS2. Our approach of using 2D MoS2 nanosheets to induce immediate aggregation of P3HT provides a facile process to control the crystallization of conjugated polymers for the development of high-performance organic electronics.

Fixation of carbon dioxide concurrently or in tandem with free radical polymerization for highly transparent polyacrylates with specific UV absorption

It is still a challenging issue to combine the coupling reaction and free radical polymerization (FRP) for well-controlled and efficient synthesis of polyacrylates bearing the cyclic carbonate group from carbon dioxide (CO2) and vinyl epoxides. This work describes the efficient catalytic synthesis of poly(2-oxo-1,3-dioxolane-4-yl)methyl methacrylate (PDOMA) from CO2 and glycidyl methacrylate (GMA) via concurrent or tandem combination of the coupling reaction and FRP. In a concurrent reaction, GMA/CO2 coupling with 100% oxirane conversion was achieved by using a nanolamellar zinc–cobalt(III) double metal cyanide complex [Zn–Co(III) DMCC] (0.30 mol% Zn related to GMA) with cetyltrimethylammonium bromide (CTAB) (0.65 mol% related to GMA) as the catalyst, and PDOMA was obtained via the concurrent free radical polymerization of carbon–carbon double bonds in the presence or absence of additional free radical initiator. In the tandem process, (2-oxo-1,3-dioxolane-4-yl)methyl methacrylate (DOMA) was firstly synthesized via GMA/CO2 coupling catalyzed by Zn–Co(III) DMCC/CTAB and purified by simply passing through a basic aluminum oxide column. DOMA could be polymerized via solution or emulsion polymerization, leading to linear PDOMA or PDOMA nanoparticles with minimized metal residues. The obtained PDOMAs were soluble in strong polar solvents and presented excellent light transmittance in a wavelength range of 314–800 nm (93%) and perfect ultraviolet (UV) absorption in a wavelength range of 200–313 nm (close to 100%), whilst most of the common polyacrylates cannot absorb UV light. In addition, the PDOMAs had tunable number-average molecular weights (Mns) of 12.0–132.0 kg mol−1 and high glass transition temperatures (Tgs) of 121.0–140.4 °C. Such CO2-based PDOMAs could be potentially used as wavelength-specific UV-absorbing materials. This work provides a simple and useful synthetic path to directly utilize CO2 by combining two reaction mechanisms.

Regio-selective synthesis of polyepichlorohydrin diol using Zn–Co(III) double metal cyanide complex

A simple one-pot ring-opening polymerization (ROP) of epichlorohydrin (ECH) was successfully performed by a heterogeneous Zn–Co(III) double metal cyanide complex (Zn–Co(III) DMCC) catalyst, affording regio-regular poly(ECH) diol with a head-to-tail content of >99% in the absence of organic solvent and/or protic compound. No cyclic or oligomer by-product was observed, and the employed Zn–Co(III) DMCC catalyst was recyclable. ROP of (R)- or (S)-ECH led to the generation of semi-crystalline poly(ECH) diol with a melting point of 81 °C or 102 °C, respectively. These regio-regular poly(ECH)s with two end hydroxyl groups are versatile platforms for ECH-based functionalized polymers.

HCAII-inspired catalysts for making carbon dioxide-based copolymers: The role of metal-hydroxide bond

The general characteristics of the active center of the catalysts (including zinc-cobalt(III) double metal cyanide complex [Zn-Co(III) DMCC]) for the copolymerization reaction of carbon dioxide (CO2) with epoxide are summarized. By comparing the active center, catalytic performance of the Zn-Co(III) DMCC (and other catalysts) with HCAII enzyme in the organism for activating CO2 (COS and CS2), we proposed that the metal-hydroxide bond (M-OH), which is the real catalytic center of human carbonic anhydride II (HCAII), is also the catalytic (initiating) center for the copolymerization. It accelerates the copolymerization and forms a closed catalytic cycle through the chain transfer reaction to water (and thus strictly meets the definition of the catalyst). In addition, the metal-hydroxide bond catalysis could well explain the oxygen/sulfur exchange reaction (O/S ER) in metal (Zn, Cr)-catalyzed copolymerization of COS (and CS2) with epoxides. Therefore, it is very promising to learn from HCAII enzyme to develop biomimetic catalyst for highly active CO2/epoxide copolymerization in a well-controlled manner under mild conditions.

Alternating and regioregular copolymers with high refractive index from COS and biomass-derived epoxides

This study describes the catalytic formation of alternating and regioregular copolymers from carbonyl sulfide (COS) and epoxides along with eugenol-based glycidyl ether (EGE) and guaiacol-based glycidyl ether (GGE), derived from eugenol and guaiacol, respectively. The (salen)CrCl [salen = N,N′-bis(salicylidene) cyclohexanediimine] complex, accompanied with various organic bases, was highly active towards the EGE/COS, GGE/COS copolymerization and EGE/GGE/COS terpolymerization. The turnover of frequency (TOF) of the (salen)CrCl complex for the EGE/COS copolymerization was up to 12 000 h−1. The number-average molecular weight (Mn) of the resultant EGE/COS copolymer was up to 62.2 kg mol−1. In the presence of 0.5–1.5 mol% chlorohydrin, which was a by-product of the synthetic process of EGE, α-Cl, ω-OH EGE/COS copolymers were obtained. This result suggests that chlorohydrin could act as a very efficient chain transfer agent for the copolymerization. The EGE/COS, GGE/COS, and EGE/GGE/COS copolymers were soluble in most of the common solvents and exhibited a high refractive index of more than 1.58 with high Abbe numbers of up to 40.4. This study provides an unprecedented and sustainable synthetic route for making soluble sulfur-rich polymers with high optical properties.