Chemical Society Reviews Blog

Hollow micro-/nanostructures have a wide range of potential applications, including catalysis, drug delivery, sensors and fuel cells. This is thanks to their unique array of properties such as high specific surface area, low density and high loading capacity.   

As any child will tell you, two sweets are better than one, while three or four are better still, and the same holds true for the number of shells in a multi-shelled hollow micro-/nanostructure. These multi-shelled structures should have significantly prolonged release times for drug delivery and improved performance in heterogeneous catalysis, lithium ion batteries and photocatalysis applications. However, with increased complexity come increased synthetic challenges.  

In their recent review, titled, ‘Multi-shelled hollow micro-/nanostructures’, Dan Wang et. al. describe the myriad of synthetic approaches for multi-shelled hollow micro-/nanostructures, before focusing on their compositional and geometric manipulation, as well as the range of potential applications. Finally, the authors look at the future challenges in the area, which include: expanding the components that can be used to make multi-shells, multi-shells whose individual shells are different, and control of inter-shell spacing.  

Preparation of a multi-shelled microstructure

Although other recent review articles have discussed hollow micro-/nanostructured materials, this is the first to focus exclusively on multi-shelled hollow structures.  

If you are interested in working on any of these challenges or others that the authors highlight, this review is a perfect starting place to get up to speed.  

To read the details, check out the Chem Soc Rev article in full:
Multi-shelled hollow micro-/nanostructures
Jian Qi, Xiaoyong Lai, Jiangyan Wang, Hongjie Tang, Hao Ren, Yu Yang, Quan Jin, Lijuan Zhang, Ranbo Yu, Guanghui Ma, Zhiguo Su, Huijun Zhao and Dan Wang
Chem. Soc. Rev., 2015, 44, DOI: 10.1039/C5CS00344J  

Chemical reactions often have reaction barriers that must be overcome in order for reactants to become products. Appreciating the origins of these barriers and more importantly quantifying their heights from raw data is of significant use to the Chemist. Therefore, the Chemist would like to have these features in the general model of reactivity which they use. A model that can predict barriers from raw data is the Valence Bond model, the focus of this quality Tutorial Review.

Sason Shaik from The Hebrew University of Jerusalem and colleagues share with the reader their insight from the development of the Valence Bond model. They focus on hydrogen atom transfer, the step most chemical oxidations begin with and which is therefore immensely important. They begin from the simplest hydrogen exchange reaction and work up to the more complex hydroxylation by Cyctochrome P450.

Valence Bond Models and the effect of different intermediates on the energy profile (bold line).

The authors take the reader through the preparation and use of valence bond diagrams and thus equip the reader with the tools required to understand mechanisms and predict chemical reactivity patterns. The authors have taken their role as tutors seriously and have provided the reader with supplementary data which they can use to work through problems and reconstruct results on their own. This focus on the reader, as a student, is very welcome and will ensure the interested reader appreciates the quality of the Valence Bond model as a useful interface between experiment and theory and between computations and understanding.

Read the Chem Soc Rev Tutorial Review in full now – for free*

A Tutorial for Understanding Chemical Reactivity Through The Valence Bond Approach
Dandamudi Usharani, Wenzhen Lai, Chunsen Li, Hui Chen, David Danovich and Sason Shaik
Chem. Soc. Rev., 2014, advance article
DOI: 10.1039/C4CS00043A

*Access is free through a registered RSC account – click here to register

Some people complain that modern life is too focussed on looks; while this may be true we can not ignore the fact that we are visual creatures. However, we have four other senses (sound, touch, smell and taste) which we can exploit. This Chem Soc Rev review by Kenneth Suslick and colleagues from the University of Illinois at Urbana-Champaign and Tehran University of Medical Sciences investigates how the sense of smell has led to developments in optical sensor arrays.

When you smell freshly mown grass, you are not identifying every chemical species, rather the smell originates from recognition of the pattern of responses of several hundred receptors. This response is what you ultimately recognise as freshly mown grass. Rather than using olfactory receptors, it is possible to use chemoresponsive colorants to generate unique optical fingerprints of any odorant or mixture of odorants. Such an approach combines the benefits of the olfactory sensing system with our preference for a visual display.

This very readable review introduces the concept and advances in the use of cross-reactive sensor arrays which allow molecular recognition via recording of unique patterns of response. Such arrays can probe a variety of chemical properties, such as: hydrophilicity, solubility, redox, hydrogen bonding, Lewis donor-acceptor and proton acidity and basicity. The variety of chemical properties that can be probed allows impressive discrimination between similar analytes.

The optoelectronic nose response to a range of volatile organic compounds.

Cross-reactive sensor array patterns can be very complex in nature. This complexity requires the use of more sophisticated statistical analysis than most chemists are comfortable with. However, an overview of the three most common statistical approaches is provided which is both informative and readily digestible by the non-expert.

Having reviewed the fundamentals of the optoelectronic nose the authors turn their attention to a myriad of applications, from the detection of toxic industrial chemicals and explosives to foods and beverages. The final section highlights how the primary limitation of sensor arrays is also their primary strength– but you will have to read the review to find out what that is!

I would strongly recommend this review on the statistical analysis section alone but I can confidently say that there will be something here for everyone.

Read this HOT Chem Soc Rev Review in full now:
Optical sensor arrays for chemical sensing: the optoelectronic nose
Jon Askim, Morteza Mahmoudi and Kenneth Suslick
Chem. Soc. Rev., 2013, Advance article
DOI: 10.1039/C3CS60179J

Iain Larmour is a guest web writer for Chem Soc Rev. He has researched a wide variety of topics during his years in the lab including nanostructured surfaces for water repellency and developing nanoparticle systems for bioanalysis by surface enhanced optical spectroscopies. He currently works in science management with a focus on responses to climate change.  In his spare time he enjoys reading, photography, art and inventing.