RSC Advances

Chen, Daomei; Li, Bin; Jiang, Liang; Duan, Deliang; Li, Yizhou; Wang, Jiaqiang; He, Jiao; Zeng, Yanbo

doi: 10.1039/c5ra18115apmid: N/A

Early diagnosis and the timely treatment of cancer are key to improving patient survival rates at present. Metal–organic frameworks (MOFs) consisting of infinite crystalline lattices with metal clusters and organic linkers may provide opportunities for the detection of cancer cells which have remained undiagnosed. Herein, we report that Fe-MIL-101 possesses an intrinsic enzyme mimicking activity similar to that found in natural horseradish peroxidase and shows highly catalytic activity even at neutral pH. The Michaelis constant (Km) of Fe-MIL-101 with H2O2 as the substrate is about 616-fold (at pH 4.0) and 20-fold (at pH 7.0) smaller than free natural horseradish peroxidase (HRP), indicating a much higher affinity for H2O2 than HRP and most of the peroxidase mimetics. Moreover, Fe-MIL-101 was successfully used to detect cancer cells by conjugating folic acid onto Fe-MIL-101 without any surface modification. The detection limit of the method for HeLa cells was estimated to be 50 cells and the reaction colour produced with 10 cells could also be observed by the naked eye. The proposed method holds considerable potential for simple, sensitive, universal, and specific cancer cell detection.

Impeng, Sarawoot; Khongpracha, Pipat; Sirijaraensre, Jakkapan; Jansang, Bavornpon; Ehara, Masahiro; Limtrakul, Jumras

doi: 10.1039/c5ra17984jpmid: N/A

Methane activation and direct oxidation to methanol on graphene (GP) and boron nitride sheet (BN) embedded Fe and FeO have been carefully studied by means of dispersion corrected DFT (PBE-D2). The strong orbital interactions between methane and the Fe active center through σ-donation and π-backdonation were found to facilitate the C–H bond dissociation. In the Fe-BN system, the π-backdonation is more dominant than that in the Fe-GP resulting in the facile C–H bond breaking with a lower energy barrier of 10.0 kcal mol−1, compared to that of 20.2 kcal mol−1. As a result, the methane C–H bond cleavage is kinetically and thermodynamically favorable on the Fe-BN system. For methane oxidation to methanol on FeO-BN compared to FeO-GP (results from RSC Adv., 2014, 4, 12572), the results reveal that the oxygen-center radical can activate the C–H bond in methane through a homolytic cleavage mechanism with reaction barriers of 20.9 kcal mol−1 and 17.5 kcal mol−1 for FeO-BN and FeO-GP, respectively. These barriers are comparable with reports on effective enzymatic systems. For methanol formation through the combination of methyl- and hydroxyl-grafted Fe-BN intermediate, the product derived from the C–H bond cleavage, required a very large energy barrier of 44.9 kcal mol−1, whereas in the Fe-GP system, the barrier was only 16.4 kcal mol−1 owing to its intermediate being less energetically stable. As a result, the conversion of methane to methanol over FeO-BN would be impeded by the incorrect stability of the intermediate. Overall, the supports play a significant role in the catalytic activity of Fe and FeO active sites for methane C–H bond cleavage and direct oxidation to methanol. This implies that the activity of the catalyst could be suitably designed by the selection of appropriate supports.

Li, Yunqi; Bastakoti, Bishnu Prasad; Abe, Hideki; Liu, Zongwen; Minett, Andrew; ALOthman, Zeid A.; Yamauchi, Yusuke

doi: 10.1039/c5ra17340jpmid: N/A

Hollow mesoporous silica (HMS) decorated with fine Pt nanoparticles is directly prepared through a dual soft-template system using a triblock copolymer, poly(styrene-b-2-vinyl pyridine-b-ethylene oxide), and a cationic surfactant, cetyltrimethylammonium bromide. The Pt nanoparticles of uniform particle size are stably embedded inside the mesoporous silica shell and possess both a huge surface area and a large total pore volume. The Pt nanoparticles supported by the mesoporous silica exhibit excellent thermal stability, which enables their application in high-temperature CO oxidation.

Stoller, Michael A.; Konda, Abhiteja; Kottwitz, Matthew A.; Morin, Stephen A.

doi: 10.1039/c5ra22742apmid: N/A

Microfluidic channels are typically fabricated in polydimethylsiloxane (PDMS) using a combination of photolithography and soft lithography. Photolithography, while ubiquitous in the fabrication of microfluidic devices, generally requires skilled technicians, expensive chemicals, and specialized equipment. This manuscript describes a simple method for the fabrication of masters for use in soft lithography that is based on combining thermoplastic “building blocks” using thermal “welding.” This approach is applicable to the fabrication of an array of devices that possess many of the basic functionalities (e.g., droplet generation, mixing, and splitting) required in microfluidics. In addition to these systems, which are routinely fabricated using photolithographically produced masters, this manuscript describes how thermoplastic building blocks can be stacked, assembled, and replicated to fabricate microfluidic devices with channel crossings and/or channels of variable cross-sectional height—geometries that normally require multiple steps of photolithography. The methods described here enable a range of scientists of varying expertise to prototype a variety of functional microfluidic devices easily and rapidly, even when access to traditional fabrication techniques or time is limited, or when an optimized design is not available.

Han, Dandan; Xiao, Ningru; Hu, He; Liu, Bao; Song, Gengxin; Yan, He

doi: 10.1039/c5ra19816jpmid: N/A

Ternary FeNi@C@polyaniline (PANI) nanocomposites, in which FeNi@C nanocapsules are surrounded by PANI, are synthesized by combining the arc-discharge process and an in situ chemical oxidative polymerization reaction. The strong interactions between the carbon shell and PANI result in the blue shift of the Raman spectrum. The effect of PANI on the electromagnetic properties of the FeNi@C nanocapsules is investigated at 2–18 GHz. The bandwidth (reflection loss (RL) < −10 dB) of the FeNi@C@PANI nanocomposites keeps constant at 3.0 GHz, but the frequency range (RL < −10 dB) shifts to a lower frequency with increasing thickness from 1.7 to 3.0 mm. For a thickness of 1.4 mm, the bandwidth of the FeNi@C@PANI nanocomposites reaches a maximum value of 5 GHz (13–18 GHz). For the FeNi@C@PANI nanocomposites, a minimum RL (RLmin) of −49.2 dB is observed at 16.6 GHz for a thickness of 1.3 mm. The RLmin of the FeNi@C@PANI nanocomposites is larger than that of the FeNi@C nanocapsules and the RLmin shifts from low to high frequency under the same absorbing thickness. The FeNi@C@PANI nanocomposite can be seen as a good candidate for lightweight, thin and strongly absorptive microwave absorbents with a broad bandwidth.

Liu, Hong; Jin, Zhitong; Xu, Zhengzheng; Zhang, Zhe; Ao, Dan

doi: 10.1039/c5ra17028apmid: N/A

ZnIn2S4–g-C3N4 sheet-on-sheet nanocomposites with different g-C3N4 contents were synthesized by a facile hydrothermal method and characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), high-resolution transmission electron microcopy (HRTEM), N2 adsorption–desorption, ultraviolet-visible diffuse reflection spectroscopy (DRS), photoluminescence (PL) spectroscopy and photoelectrochemical (PEC) experiments. The photocatalytic activities of these samples were evaluated by the photocatalytic H2-production and degradation of organic pollutants (methyl orange and phenol) under visible-light illumination (λ > 420 nm). The results showed that the ZnIn2S4–g-C3N4 composite photocatalysts displayed higher photocatalytic activity than the pristine g-C3N4 and ZnIn2S4 both for H2-evolution and degradation of pollutants. The optimal g-C3N4 content was determined to be 40 wt%, and the corresponding H2-production rate was 953.5 μmol h−1 g−1, which was about 1.91 times higher than that of pure ZnIn2S4. The enhanced photocatalytic activity of ZnIn2S4–g-C3N4 composites should be attributed to the well-matched band structure and intimate contact interfaces between ZnIn2S4 and g-C3N4, which led to the effective transfer and separation of the photogenerated charge carriers. Moreover, the ZnIn2S4–g-C3N4 composites showed excellent stability during the photocatalytic reactions under visible light. A possible mechanism of the enhanced photocatalytic activity of ZnIn2S4–g-C3N4 composites was proposed and supported by the PL and PEC results.

Bueno, Lígia; Cottell, Alison; Reddy, Subrayal M.; Paixão, Thiago R. L. C.

doi: 10.1039/c5ra19874gpmid: N/A

We report the use of a colorimetric plastic-based device to discriminate four pathogenic bacteria: Klebsiella pneumoniae, Proteus vulgaris, Proteus mirabilis and Escherichia coli. The colour changes of the plastic membranes were analysed with RGB values extracted from dye-integrated polymeric membrane images obtained with a smartphone and used as input data for non-supervised pattern recognition methods.

Lai, Chenhuan; Tu, Maobing; Yong, Qiang; Yu, Shiyuan

doi: 10.1039/c5ra22308cpmid: N/A

The roles of solvent extractable lignin and residual bulk lignin in enzymatic hydrolysis of Avicel and lignocellulosic biomass were distinguished in this study. Solvent extractable lignin removal reduced the 72 h hydrolysis yields of dilute acid pretreated sweetgum (DASG) and organosolv pretreated sweetgum (OPSG) from 38.1% to 31.8% and from 69.9 to 49.3%, respectively. On the contrary, residual bulk lignin removal enhanced the 72 h hydrolysis yields of DASG and OPSG to 91.7% and 90.5%, respectively. The isolated lignins were added into enzymatic hydrolysis of Avicel, which revealed the positive effect of extractable lignin and the negative effect of residual bulk lignin on enzymatic hydrolysis. The cellulase distribution during the hydrolysis and cellulase adsorption indicated that the extractable lignin could counter the negative effect of residual bulk lignin by reducing the non-productive binding between cellulase and bulk lignin.

Luan, Jiabin; Shen, Wenjia; Chen, Chang; Lei, Kewen; Yu, Lin; Ding, Jiandong

doi: 10.1039/c5ra22307epmid: N/A

A novel coordination-responsive block copolymer composed of polyether and polyester with selenium at the center was designed and synthesized for controlled drug delivery. The aqueous system of the new copolymer was a free-flowing solution at ambient temperature and turned into a semi-solid thermogel at body temperature. We demonstrate that the selenium-containing copolymer is capable of coordinating with the antitumor drug cisplatin. The efficient coordination between them significantly increased the loading capacity of cisplatin in the selenium-containing thermogel matrix, and the presence of glutathione in the release medium triggered the cisplatin release by coordination competition in a sustained release manner.

Qian, Weijin; Li, Mengjie; Chen, Lihong; Zhang, Jianghui; Dong, Changkun

doi: 10.1039/c5ra19182cpmid: N/A

The application of carbon nanotubes (CNTs) as a thermo-electrochemical cell (TEC) electrode is still difficult due to their weak contact with the substrate during the electrophoretic deposition (EPD) method. In this study, by doping the suspension of the CNTs with Mg2+ and Ag powder, Ag–MgO–CNT nanocomposites were successfully prepared on a stainless steel (SS) substrate using the EPD method. The products were confirmed using characterization by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray and X-ray photoelectron spectroscopy. The TEC performance of the Ag–MgO–CNTs nanocomposite electrodes was significantly improved due to their higher conductivity, thermal conductivity and improved adhesion between the composite film and the SS substrate, depending on the concentrations of the Ag powder. The results suggest that constructing Ag–MgO–CNTs nanocomposite electrodes can effectively enhance the performance of CNTs-based TECs, which might be a promising way for energy harvesting using CNTs-based TECs prepared via the EPD technique.