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Archive for the ‘Materials’ Category

Nanoconfinement leads to increased catalytic stability

29 Nov 2012

Steam reforming, where hydrogen gas is produced from hydrocarbon fuels such as natural gas, is an important industrial catalytic process. Nickel is the catalyst of choice due to its low cost and high C-C bond rupture activity, and zirconia (ZrO₂) is widely used as the catalytic support due to its thermal and chemical stability, moderate acidity and surface oxygen mobility. The same supported Ni/ZrO₂ catalyst is a promising candidate for ethanol steam reforming (ESR), but its deactivation caused by sintering and coke deposition remains a problem.

Jinlong Gong and researchers from Tianjin University used a surfactant-assisted method to prepare a nanocomposite Ni@ZrO₂ catalyst made up of nickel nanoparticles distributed evenly throughout a similarly sized zirconia matrix. The new catalyst demonstrated higher activity and selectivity for the conversion of ethanol into CO₂ and H₂. Almost complete conversion of ethanol over a 50 hour period was observed, while the activity of the traditional Ni/ZrO₂ catalyst decreased continually after just six hours.

The even distribution of metal nanoparticles throughout the matrix allows the pore structure of the solid to be maintained while increasing the accessibility of the catalytically active nickel. The larger metal-oxide interface promotes the removal of carbon deposits while the “confinement effect” prevents the nickel metal from sintering. As highlighted in a recent C&EN article, these promising catalytic properties suggest that the synthetic methodology may be useful for the design of metal catalysts for other processes, such as dehydrogenation, that encounter similar problems.

Read this HOT Chem Comm article today (free to access until the 27th December):

A Ni@ZrO₂ nanocomposite for ethanol steam reforming: enhanced stability via a strong metal-oxide interaction
Shuirong Li, Chengxi Zhang, Zhiqi Huang, Gaowei Wu and Jinlong Gong
Chem Commun., 2013, Advance Article
DOI: 10.1039/C2CC37109J

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Medicinal hope for injectable hydrogels

08 Oct 2012

Injectable hydrogels with dual ionic properties, biodegradability and low cytotoxicity have been developed by South Korean scientists to deliver proteins therapeutically.

Doo Sung Lee and colleagues from Sungkyunkwan University developed an amphoteric copolymer to form dually cationic and anionic hydrogels, in response to pH and temperature changes. The amphoteric nature of the polymer means it should bind to both cationic and anionic biomolecules, and helps sustained co-delivery of them.

The copolymer changing from sol to gel

Read more in Chemistry World or download Lee’s communication in ChemComm.

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Metal-free resins can drive down cost of solar energy

08 Oct 2012

Solar farm Costly metals in some solar cells could be replaced by cheap resins, according to Korean research.

Dye-sensitised solar cells (DSSCs) are an important class of solar cells, which demonstrate a number of important attributes, such as low cost, flexibility and good efficiency. It is perhaps the most actively researched solar cell technology. However, it is still hindered by expensive components.

Currently, a third of the cost of DSSCs could go towards the noble metal-based dyes used to sensitise the titania photocatalyst, allowing it to harvest the more useful visible part of the spectrum. However, Wonyong Choi and his group at Pohang University of Science and Technology have replaced these dyes with a simple and cheap phenolic resin.

Read more in Chemistry World or read Choi’s communication in ChemComm.

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Refinery test for mesostructured zeolite

12 Sep 2012

The Y zeolite is used as a catalyst for fluid catalytic cracking. It has a high surface area and large pores and is thermally and hydrothermally stable. But scientists are working on improving the catalyst for a better performance. One reason is that the 7.4Å micropores are limited in terms of size of hydrocarbon that they can take in. The process involves diffusion of large hydrocarbon molecules into the crystals and diffusion of the desired intermediate cracking products (diesel or light oil, gasoline and liquefied petroleum gases) out.

Introducing wider pores allows large hydrocarbon molecules to go through the process. Scientists from Spain had recently carried out a templating process (using a surfactant) to introduce highly controlled mesoporosity into zeolites. This led to improved catalytic selectivity, in which more gasoline, light oil and liquefied petroleum gas were obtained.

The team have now scaled up the catalyst and tested its hydrothermal stability and catalytic cracking performance in a refinery. The catalyst showed much better product selectivity compared to the current catalyst, says the team.

Link to journal article
A mesostructured Y zeolite as a superior FCC catalyst – from lab to refinery
J Garcia-Martinez, K Li and G Krishnaiah
Chem. Commun., 2012, DOI: 10.1039/c2cc35659g

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Overcoat makes carbon quantum dots biocompatible

22 Aug 2012

Quantum dots are currently being developed for a variety of applications, including as sensors and cellular tags. Semiconductor quantum dots are attractive for their high fluorescence quantum yields but the toxicity of some of the metals involved, such as cadmium, pose a problem for biological applications.

Carbon quantum dots (CQDs) offer an alternative however when transferred into aqueous solution they possess low quantum yields. The problem is how do you harness the higher fluorescence of CQDs prepared in an organic solvent for biological applications?

To answer this question John Callan and his team have employed an amphiphilic polymer to act as an overcoat and transfer agent for the CQDs. Surprisingly they found that the transfer actually improved the quantum yield rather than the normally expected repression when ligand exchange is used. These aqueous carbon quantum dots were taken up into cells and were found to be non-toxic.

The development of inexpensive and biocompatible quantum dots with an improved quantum yield holds great potential for a wide range of future biological applications.

To find out more, download the ChemComm article today (free to access for a limited period).

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Lab-in-a-syringe approach to separating biomarkers from blood samples

16 Aug 2012

Scientists in China have developed a novel method to prepare ordered mesoporous silica fibres. The fibres can enrich endogenous peptides in under three minutes with a lab-in-syringe approach. The technique does not need electrical devices such as a centrifugal machine or vortex shaker.

The team says that the lab-in-syringe approach could be applied to separation sciences and it could be used in drug delivery, catalysis, and sensor and optical devices.

Electrospinning-based synthesis of highly ordered mesoporous silica fiber for lab-in-syringe enrichment of plasma peptides
Gangtian Zhu, Xiao-Shui Li, Xiao-Meng Fu, Juan-Yuan Wu, Bi-Feng Yuan and Y.-Q. Feng
DOI: 10.1039/C2CC34761J

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Cheaper dye-sensitised solar cells

16 Aug 2012

Scientists in Germany and Switzerland have used metal-free plastic cathodes to replace expensive transparent conducting oxide-coated electrodes in dye-sensitised solar cells.

The team says that a record metal-free plastic cathode cell performance of 4.22% can be achieved at full sun, which is 27% less than the standard value of platinised transparent conducting oxide-coated electrodes, but at a fraction of the cost.

Towards flexibility: Metal free plastic cathodes for Dye sensitized solar cells
Shahzada Ahmad, Elisa Dell’Orto, Jun-Ho Yum, Florian Kessler, Mohammad Khaja Nazeeruddin and Michael Gratzel
DOI: 10.1039/C2CC35038F

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Making light work of hydrogel formation

14 Aug 2012

UK scientists have developed a new way to make hydrogels using light. The hydrogels could be used in a range of applications from cell culture to biosensors.

Graphical abstract: Dipeptide hydrogelation triggered via ultraviolet light Dave Adams, at the University of Liverpool, and colleagues made the hydrogels from dipeptide conjugates using UV light to trigger the gelation. Unlike previous light-activated gelations, the team used a photoacid generator (a molecule that is photolysed by light to produce an acid) to lower the pH of the gelator solution below the apparent pKa of the gelators, resulting in gelation.

The team showed that they could pattern the hydrogel using a photomask. The patterned channels of gels could be used in microfluidics, biosensors and synthetic biomaterials, the team suggest.

Read more about this research in Adams’ ChemComm communication, free to access for a limited period.

Also of interest:
Chem Soc Rev critical review: Supramolecular gels formed from multi-component low molecular weight species

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Luminogenic materials have a bright future

30 Jul 2012

Luminogenic materials are a hot topic of research due to their potential applications in biotechnology and memory systems. But most luminogenic materials undergo aggregation-caused quenching (ACQ) in the solid state. This is when the dye molecules near each other aggregate and form species that weaken the material’s emission.

Ben Zhong Tang and his team have been researching materials that instead exhibit aggregation-induced emission (AIE). This makes the preparation of solid state luminogens much simpler as aggregation increases the activity. Unfortunately, there are few AIE-active emitters in the longer wavelength region, which is of interest for biotechnology applications.

Tang’s team have addressed this oversight by developing a novel luminogen which couples the AIE property of tetraphenylethene and the longer wavelength activity of a hemicyanine dye. The emission properties of the resultant crystals can be readily tuned by the solvent molecules in the solution they are grown from.

: Crystochromism of the novel luminogen

Most interestingly, the prepared luminogen shows crystochromism: a strong yellow emission in its thermodynamically stable crystalline form and a red colour in its metastable amorphous form. These changes are fully reversible, with grinding, heating or fuming causing the change in the luminogen’s crystallinity.

To find out more, download the ChemComm article today.

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Silica sheets to deliver DNA into cells for disease prevention and treatment

17 Jul 2012

Scientists in Japan have made a new DNA delivery substrate based on networks of bio-friendly upright silica sheets. The network of sheets forms a porous film on to which they can immobilise DNA, ready for delivery (transfection) into cells. The transfection efficiency of the silica film is approximately double that of solution-based transfection. Gene transfection is a potential method for preventing and treating diseases and analysing cell functions.

Link to journal article
Silica-based Gene Reverse Transfection: Upright Nanosheet Network for Promoted DNA Delivery to Cell
Q Ji et al
Chem. Commun., 2012, DOI: 10.1039/c2cc34289h

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