RSC Advances

Yakacki, C. M.; Saed, M.; Nair, D. P.; Gong, T.; Reed, S. M.; Bowman, C. N.

doi: 10.1039/c5ra01039jpmid: N/A

This study introduces an unexplored method to synthesize and program liquid-crystalline elastomers (LCEs) based on a two-stage thiol–acrylate Michael addition and photopolymerization (TAMAP) reaction. This methodology can be used to program permanently-aligned monodomain samples capable of “hands-free” shape switching as well as offer spatio-temporal control over liquid-crystalline behaviour. LCE networks were shown to have a cytocompatible response at both stages of the reaction.

Rostami, Ali; SalmanOgli, Ahmad; Farhadnia, Farshad; Dolatyari, Mahbobeh; Rostami, Ghassem; Pişkin, Erhan

doi: 10.1039/c4ra15867apmid: N/A

In this study, a portable nanosensor for the early and easy detection of carcinoma tumors was designed and simulated. The nanosensor consists of deposited nanoparticles, which have a regular distance from each other. It has high sensitivity to the alteration of electromagnetic fields, which are scattered from different tissues (normal and tumor). Normal tissue permittivity differs from the permittivity of tumors; hence, their interaction with electromagnetic waves will lead to different results in the case of an electrical field and its gradient profile. It means that non-uniformity will occur and this is a meaningful signal for detection. Nevertheless, it is obvious that due to the tissue absorption coefficient, scattered photons will be very negligible and a small fraction of the photons will reach the detector. Hence, in this paper, a sensor based on nanoparticles is proposed, which has enough sensitivity to pick up scattered photons, amplify, and detect them. It should be noted that the roles of the nanosensor between the body surface and detector are signal amplification and sampling via the nanoparticle plasmonic effect. This means that the designed nanoparticles sample the scattered waves and amplify them in the near-field. Finally, our design and simulation results show that the digitized signals could be easily and clearly detected by force or temperature detectors. Thus, easy breast tomography will be carried out with no need for clinics and their equipment.

Saravanan, K.; Kao, C.-H.; Shao, Y.-C.; Wang, Y.-F.; Wang, B.-Y.; Wang, H. T.; Tsai, C.-J.; Lin, W.-C.; Pao, C.-W.; Tsai, H.-M.; Jang, L.-Y.; Lin, H. J.; Lee, J.-F.; Pong, W.-F.

doi: 10.1039/c4ra15683hpmid: N/A

We study the magnetic anisotropic properties of as-grown and annealed Pd/Co/Pd trilayer films based on their atomic and electronic structures using extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES) spectroscopy and magnetic circular dichroism (XMCD) measurements. The annealed film exhibits interesting perpendicular magnetic anisotropy (PMA) whereas the as-grown film exhibits in-plane anisotropy. Cross-sectional transmission electron microscopic analysis together with the Co K-edge EXAFS results confirm the formation of an ordered-alloy CoPd phase in the annealed film, whereas the as-grown film has an hcp Co-like phase. Co L3,2-edge XMCD measurements reveal an enhanced ratio of the Co 3d orbital to spin moments of the annealed film providing evidence of the observed PMA upon annealing.

Liang, Feng-Xia; Zhang, Deng-Yue; Zou, Yi-feng; Hu, Han; Zhang, Teng-Fei; Wu, Yu-Cheng; Luo, Lin-Bao

doi: 10.1039/c4ra16781cpmid: N/A

In this study, we present a simple oxide assisted p-type doping of Si nanostructures by evaporating a mixed powder composed of SiB6 and SiO. It was found that Si nanoribbons (Si NRs) which can be obtained at high SiB6 content, will give way to Si nanowires (Si NWs) when the content of SiB6 in the mixed powder was reduced. According to our transport measurement of field effect transistors (FETs) assembled on individual Si nanostructures, the as-prepared Si nanostructures with different boron doping levels all exhibit typical p-type conduction characteristics. Additionally, the electrical conductivity of the Si nanostructures can be tuned over 7 orders of magnitude from 8.98 × 102 S cm−1 for the highly doped sample to 3.36 × 10−5 S cm−1 for the lightly doped sample. We also assembled a nano-photodetector based on monolayer graphene and the as-prepared Si nanostructures, which exhibits ultra-sensitivity to 850 nm near infrared light (NIR) illumination with a nanosecond response speed (τrise/τfall: 181/233 ns). The generality of the above results suggest that the Si nanostructures are promising building blocks for future electronic and optoelectronic device applications.

Sawant, Ratnnadeep C.; Liao, Ying-Ju; Lin, Yi-Jyun; Badsara, Satpal Singh; Luo, Shun-Yuan

doi: 10.1039/c4ra17050dpmid: N/A

A concise route to access the key disaccharide repeating unit (IdoA–GlcN) of heparan sulfate is described. The synthesis was accomplished by commercially available diacetone α-d-glucose to functional group transformations, which led to the formation of a l-iduronate donor. This l-iduronate donor was subsequently coupled with a glucosyl acceptor to form the corresponding key disaccharide repeating unit (IdoA–GlcN) of heparan sulfate in good overall yield.

Jiang, Xiang; Tao, Bo; Yu, Xiaoli; Wang, Yunhong; Xia, Hua

doi: 10.1039/c4ra16545dpmid: N/A

Three cyano-bridged nickel(ii) complexes, namely, [NiL1][Ni(CN)4]·3H2O (1), [NiL2][Ni(CN)4]·H2O·CH3CN (2) and [NiL3][Ni(CN)4]·3H2O (3) (L1 = 1,3,6,8,11,14-hexaazatricyclo[12.2.1.18,11]octadecane, L2 = 1,3,6.8.12,15-hexaazatricyclo[13.3.1.18,12]eicosane and L3 = 1,3,6,9,11,14-hexaazatricyclo[12.2.1.16,9]octadecane), have been synthesized and characterized based on different macrocyclic metallic tectons and diamagnetic [Ni(CN)4]2−. Single crystal X-ray analyses reveal that complexes 1–3 exhibit a similar cyano-bridged one-dimensional chain structure, in which one nickel(ii) ion is coordinated by four nitrogen atoms from the macrocyclic ligand and two nitrogen atoms from the bridging cyanide ligands, while the residual nickel(ii) ion is coordinated by four cyanide ligands. Interestingly, regulated by the peripheral macrocyclic ligand, complex 1 features an unexpected large porous structure with a pore size of 1 nm, which shows pronounced two-step adsorption of CO2 gas at 195 K. In additional, the magnetic properties of complexes 1–3 show the presence of weak intrachain ferromagnetic interactions between the paramagnetic nickel(ii) ions through the diamagnetic [Ni(CN)4]2− anions.

Li, Hui; Chen, Qi; Schönbeck, Christian; Han, Bao-Hang

doi: 10.1039/c4ra07523dpmid: N/A

Pillar[5]arenes have attracted much attention as a new member of macrocycles due to their unique symmetrical pillar architecture. Pillar[5]arenes are mostly soluble in organic solvents and slightly soluble in water, thus their application in aqueous media has been limited as a result. It is therefore necessary to design water-soluble pillar[5]arene derivatives. Herein, by the introduction of neutral sugar moieties at both upper and lower rims via click reaction, a neutral water-soluble pillar[5]arene (P5AG) was prepared and characterized well. Furthermore, the host–guest interaction between P5AG and fullerene was investigated in both organic medium and aqueous solution. The host–guest complexation was confirmed by fluorescence, nuclear magnetic resonance, ultraviolet-visible, and Raman spectroscopy.

Sun, JiaQin; Wei, Wei; Xu, YaZhen; Qu, JieHao; Liu, XiangDong; Endo, Takeshi

doi: 10.1039/c4ra16582apmid: N/A

Five commercially available amines: m-phenylenediamine (A1), m-xylylenediamine (A2), isophorone diamine (A3), trimethylhexamethylenediamine (A4), and 4,4′-diaminodiphenyl sulfone (A5), were examined as nucleophilic hardeners for bis-benzoxazine monomers based on aniline paired with bisphenol-A (BA-a) or bisphenol-F (BF-a). The reactivities and reaction mechanisms of their mixtures with BA-a were investigated using FTIR and NMR spectroscopy, DSC, and HPLC techniques. It was found that BA-a rapidly cured with the amines upon heating at 120 °C or 150 °C. The cure rate was similar to the amine/epoxy curing process in practical uses, and significantly faster than the ring-opening polymerization of bulk BA-a. The possible reaction mechanism was supported by the experimental results and includes three successive steps: (i) nucleophilic substitution at the carbon atom (O–C–N) in the oxazine ring by the amine, (ii) thermal decomposition of the resulting aminomethanaminium structure, and (iii) electrophilic addition of the newly formed iminium ion with the aromatic ring to form stable aminomethylphenol structures. These findings are helpful to improve the thermosetting resins in terms of their chemical structure, material properties, and processability.

Bao, Rui-Ying; Yang, Wei; Liu, Zheng-Ying; Xie, Bang-Hu; Yang, Ming-Bo

doi: 10.1039/c5ra00691kpmid: N/A

The effect of melt blending with poly(methyl methacrylate) (PMMA), a miscible polymer with polylactide (PLA), on the crystallization and melting behaviors and crystalline structure of high-molecular-weight poly(l-lactide)/poly(d-lactide) (PLLA/PDLA) blend was investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). Due to the decreased segmental mobility of PLA chains and the dilution effect of the introduced PMMA, the crystallization of PLA is hindered. The polymorphic crystallization of the PLLA/PDLA blend can be tailored by the amount of PMMA and dynamic and isothermal crystallization conditions. The formation of stereocomplex (sc) crystallites is favored for the blends containing PMMA lower than 50 wt% during cold crystallization. During isothermal melt crystallization, the formation of sc crystallites is always accompanied by the generation of homochiral (hc) crystallites at a crystallization temperature (Tc) ranging from 110 to 160 °C for neat PLLA/PDLA blend, while the crystallization window for exclusive sc crystallites is widened to 160 °C, 140–160 °C, and 110–150 °C for PLLA/PDLA blends containing 10, 25, and 50 wt% PMMA, respectively. Especially, the formation of sc crystallites can be enhanced over the entire Tc range of 110–160 °C when the PMMA content is lower than 25 wt%. The enhanced sc crystallite formation can be ascribed to the reduced crystallization competition resulting from highly restricted hc crystallization. With the PMMA content increasing to 75 wt%, the inhibition effect on the crystallization of PLA suppresses either hc or sc crystallization.

Gao, Yong; Rafaniello, William; Toksoy, Muhammet Fatih; Munhollon, Tyler; Haber, Richard

doi: 10.1039/c4ra16279jpmid: N/A

In the processing of crystalline boron carbide, boron oxide and carbon precursors are used as feedstock into a carbothermal reduction process reactor. The uniformity of the precursor blends has a dramatic effect on the homogeneity of the resultant boron carbide. In boron carbide precursor preparation via a wet process, boric acid is usually dissolved into water at 80 °C and then mixed with carbon and dried at 120 °C, followed by calcination then comminution to obtain the desired feed particle size. However, controlling the crystallization and particle size of boric acid is challenging and there are no prior published studies dealing with this issue. In this study, a simple process demonstrated that adding hexane to the boric acid water solution during the drying can achieve a highly crystallized powder with a narrow particle size distribution. Hexane generates supersaturation during the recrystallization of boric acid by increasing boric acid nucleation. The hexane can inhibit boric acid crystal growth by isolating the formed nuclei thus providing a barrier to molecular diffusion. The water to hexane volumetric ratio, suitable processing parameters, and optimized dispersant amount were investigated. It was found that the process of mixing the optimum solution at room temperature and then drying it at 120 °C produced the relatively uniform 0.3 μm particles. By adding 1.5 wt% dispersant (Triton X-100) to the mixture, 20 nm boric acid particle size can be obtained. The boron carbide powder fabricated by carbothermal process from the modified precursor demonstrated a finer and more uniform particle size with lower free carbon content. The precursor calcination temperature could be lowered from 600 °C to 450 °C.