Archive for the ‘Blog writer’ Category

Deep sight into the brain: organic nanoparticles for imaging in the second near-infrared window

Researchers have long been interested in peering into the brain. Added to the inherent challenge of imaging through biological medium, the skull presents a major barrier that highly attenuates light.

To overcome this barrier, in a recent communication in Materials Horizons, Guo et al. have synthesized an organic nanoparticle for photoacoustic imaging with absorbance in the second near-infrared window. At this wavelength, there is relatively low scattering from tissue allowing for deeper penetration of light.

Photoacoustic images of a brain tumor after nanoparticle injection. The grey ultrasound image shows the skin and the skull margin, and the green signal indicates the nanoparticle distribution. Image adapted from Guo et al., Mater. Horiz., 2017, Advance Article with permission from The Royal Society of Chemistry. 

Nanoparticles were made from benzodithiophene-benzobithiadiazole donor-acceptor pairs co-polymerized and nanoprecipitated using biocompatible materials. When these imaging nanoparticles were applied to mice with orthotopic brain tumors, tumors 3.4 nm below the skull were resolved with a nearly 100-fold increase in photoacoustic signal compared to before intravenous administration of nanoparticles. The stable, high contrast photoacoustic imaging nanoparticle presented in this work offers a versatile platform for simple chemical modifications such as ligand targeting or drug loading.

Future work remains on the horizon to advance these materials for imaging through the ~5 mm thickness of human skulls.

 

Read the full article here:
Bing Guo, Zonghai Sheng, Kenry, Dehong Hu, Xiangwei Lin, Shidang Xu, Chengbo Liu, Hairong Zheng and Bin Liu

 

Ester Kwon is a member of the Community Board for Materials Horizons. Currently, she works as an Assistant Professor in the Department of Bioengineering at University of California San Diego, USA. Check out her personal website here.

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The pursuit of solid-state electrolytes for lithium batteries: from comprehensive insight to emerging horizons

Conventional lithium rechargeable batteries contain solid electrodes and liquid electrolytes, which can have potential security risks concerning volatilization, flammability and explosion. Because of the widely acknowledged safety benefits of solid electrolytes over their liquid counterparts, the application of solid-state batteries has been widely envisioned. Recently, a review of solid-state electrolytes for lithium batteries has been published in Materials Horizons, by Renjie Chen’s group at Beijing Institute of Technology.
They discuss existing solid electrolytes including inorganic solid electrolytes, solid polymer electrolytes, and composite solid electrolytes, and present conductive mechanisms of these conductors in detail. However, large-scale implementation of all-solid-state batteries is still some way off because unsolved severe limitations have been encountered. This review systematically summarizes and visually displays the current limitations of solid electrolytes and efforts to overcome them with the objective of large-scale development. Given that the issues limiting solid electrolytes mainly derive from their structure activity relationships, so the main part has been divided into four sections: bulk, surface, interface and grain boundary.
Though this review, Professor Renjie Chen intends to convey the messages that the field of solid-state lithium batteries is multidisciplinary and joint experimental, computational and practical investigations could provide comprehensive insight into solid electrolytes. If the current limitations are broken though, it is hoped that this field will advance to large-scale development in the near future.

Categories of the existing solid electrolytes

Read the full article here:
The pursuit of solid-state electrolytes for lithium batteries: from comprehensive insight to emerging horizons
Renjie Chen, Wenjie Qu, Xing Guo, Li Li and Feng Wu
Mater. Horiz., 2016, 3, 487-516

 

Mengye Wang is a member of the Community Board for Materials Horizons. Currently, she works as a postdoctoral fellow in the Department of Applied Physics at The Hong Kong Polytechnic University. She has a keen interest in advanced materials for environmental and energy applications, including photocatalysis and electrocatalysis.

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A skin-like sensor based on a stimuli-responsive hydrogel

A novel type of multifunctional skin-like sensor based on a 3D printed thermo-responsive hydrogel has been reported in a new article, published in Materials Horizons. This study presents a simple strategy to transduce the volume phase transition behaviors of stimuli-responsive hydrogels into reliable electrical signals, which might be helpful to develop biocompatible skin-like sensors based on hydrogels with a wide range of sensory capabilities.

 

The strategy, developed by Professor Peiyi Wu and colleagues at Fudan University,  is based on two key points:

  1. Capacitive sensors in a parallel-plate configuration are sensitive to changes of the conductive area, thus allowing area changes (corresponding to volume phase transition behaviors) of stimuli-responsive ion-conducting hydrogels to be transduced into capacitance signals.
  2. Microstructuring the conductive layers with a sub-millimeter resolution enhances the relative area changes upon stimulation, thereby magnifying the capacitive response signals.

A thermo-responsive hydrogel was used in this work and the microstructure was fabricated by an advanced 3D printing technique. Wu’s group demonstrated that the microstructured hydrogel effectively magnified the capacitive area changes upon external stimuli (i.e., temperature and pressure). The prepared skin-like sensor could sense body temperatures, gentle finger touches and finger bending motion.

 

This work not only indicates that stimuli-responsive hydrogels are promising candidates for artificially intelligent skins, but might also enrich the design of skin-like sensors for future artificial intelligence, wearable devices and human/machine inter-action applications.

 

A 3D printed thermo-responsive hydrogel is designed as a novel multifunctional skin-like sensor, which could sense body temperature, gentle finger touches and finger bending motion.

 

Read the full article here:
Zhouyue Lei, Quankang Wang and Peiyi Wu
Mater. Horiz., 2017, Advance Article

 

Mengye Wang is a member of the Community Board for Materials Horizons. Currently, she works as a postdoctoral fellow in the Department of Applied Physics at The Hong Kong Polytechnic University. She has a keen interest in advanced materials for environmental and energy applications, including photocatalysis and electrocatalysis.

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Band-engineering in lead-free double perovskites

Hybrid double perovskites have recently gained a vast amount of attention in the research area of photovoltaics as lead-free alternatives to the ground-breaking parent material [CH3NH3]PbI3.1 In double perovskites with the general formula A2B’B’’X6, two Pb2+ cations are effectively replaced with a monovalent B’ and a trivalent B’’ cation. Among the many fascinating properties of hybrid inorganic-organic perovskites, it is arguably the combination of strong light absorbance and long carrier lifetimes that make them so interesting for photovoltaic applications and light-emission devices. Recent experimental and theoretical studies on [CH3NH3]PbI3 revealed a direct-indirect character of the bandgap, i.e. [CH3NH3]PbI3 exhibits a direct band gap which is only approximately 47-60 meV higher in energy than the indirect band gap. Presumably, this is the origin of the paradox of strong absorption and long charge carrier lifetimes. When now turning our attention to lead free double perovskites, examples such as [CH3NH3]2KBiCl6 and [CH3NH3]2AgBiBr6 exhibit an indirect band gap,1 hence unfavourable light absorption properties. The symmetry mismatch that leads to the indirect band gap in such materials was recently studied by D. O. Scanlon and A. Zunger theoretically.2,3 Consequently, it is important to ask the question: is it possible to experimentally design a direct band gap in double perovskites?

In the recent article in Materials Horizons, ‘Designing Indirect-Direct Bandgap Transitions in Double Perovskites’,4 T. M. McQueen and co-workers have tackled this important question, studying the solid solution Cs2AgIn1-xSbxCl6 as a prototypical example. By wisely choosing B’ and B’’, a direct band gap in Cs2AgInCl6 has been achieved. The beauty lies in the simplicity of the concept – the understanding of band theory, i.e. symmetry and formation of bands with s-type and p-type character, see Figure 1. Going along the solid solution Cs2AgIn1-xSbxCl6, the valence band remains basically unchanged, whilst the character of the conduction band is continuously altered from s-type to p-type character. Clearly, the use of a chloride and in turn the ionic character of the solid with a band-gap larger than 3.5 eV limits the application of Cs2AgInCl6 in optoelectronics. However, the results depict a textbook example of how to manipulate properties in crystalline materials and open exciting opportunities for going forward in the field. For instance, one can easily envision a computational screening study of potential A2B’B’’X6 perovskites by using symmetry-based descriptors. Furthermore, it is important to note, that band engineering is a common concept in related areas of materials science, such as thermoelectrics and magnetic materials, and is a common tool for solid state chemists in general. Therefore, it is refreshing to see that band engineering now enters arguably one of the most fascinating developments of materials science within the last decade.

 

Figure 1. Schematic presentation of the orbital overlap (a) and the energy as a function of k for bands of s and p-σ orbitals (b) in a linear chain.

 

[1] F. Wei, Z. Deng, S. Sun, F. Xie, G. Kieslich, D. M. Evans, M. A. Carpenter, P. D. Bristowe, A. K. Cheetham ‘The synthesis, structure and electronic properties of a lead-free hybrid inorganic-organic double perovskites (MA)2KBiCl6 (MA = methylammonium)Mater. Horiz. 2016, 3, 328.

[2] C. N. Savory, A. Walsh and D. O. Scanlon ‘Can Pb-Free Halide Double Perovskites Support High-Efficiency Solar Cells?’ ACS Energy Lett. 2016, 1, 949.

[3] X.-G. Zhao, D. Yang, Y. Sun, T. Li, L. Zhang, L. Yu, A. Zunger ‘Cu-In Halide Perovskite Solar Absorbers’ J. Am. Chem. Soc. 2017, 139, 6718.

[4] T. Thao Tran, J. R. Panella, J. R. Chamorro, J. R. Morey, T. M. McQueen ‘Designing Indirect-Direct Bandgap Transitions in Double PerovskitesMater. Horiz. 2017, DOI: 10.1039/C7MH00239D.

 

Dr Gregor Kieslich is a Liebig-Fellow at Department of Chemistry, Technical University of Munich and is a member of the Community Board for Materials Horizons. He is an inorganic chemist focusing on crystal chemistry and structure–property relations in functional solids and hybrid frameworks: https://kieslichresearch.wordpress.com/

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A laser “writing” method for easily adjustable and complex 3D structures – a new HOT article

Different 3D structures created

Photographs of different 3D shapes generated from the same stretched Nafion/PDA films treated with a NIR laser with different facular region shapes.

A new and highly adaptable way to make 3D structures in a wide range of different shapes has been reported in a new HOT article, published in Materials Horizons. The technique allows adjustment of both the shape transition process and the final shape at the same time.

The strategy, which Jian Ji’s group at Zhejiang University describe as a “writing” process, uses polymer nanosheets as blank “paper”. These are guided into making specific shape changes with a near infra-red laser beam “pen”. By controlling which shape changes happen at which time, several sheets can be woven together into a complex interlocking structure. Unlike previous techniques, the order of these changes can be easily altered to change the interlocking pattern.

Ji’s group used pre-stretched composite sheets of Nafion, a shape memory polymer, and polydopamine. When a NIR laser was applied to specific parts of the nanosheet, the polydopamine converted the light energy into heat. This caused internal stress between the heated and non-heated parts, triggering a shape transition of the sheet to relieve the stress. Changing the shape or intensity of the laser beam or where it was applied modulated the shape change, giving rise to a huge number of possible shapes.

Because the nanosheets don’t require special pretreatment before forming each particular shape, a variety of shapes can be made from the same starting material in quick succession. The technique could in future be used to make “personalised” components for the healthcare industry.

Read the full article here:
A ‘‘writing’’ strategy for shape transition with infinitely adjustable shaping sequences and in situ tunable 3D structures
Tingting Chen, Huan Li, Zuhong Li, Qiao Jin and Jian Ji
Mater. Horiz., 2016, DOI: 10.1039/C6MH00295A

Susannah May is a guest web writer for the RSC Journal blogs. She currently works in the Publishing Department of the Royal Society of Chemistry, and has a keen interest in biology and biomedicine, and the frontiers of their intersection with chemistry. She can be found on Twitter using @SusannahCIMay.

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