Archive for the ‘Physical’ Category

Buckyball’s Hydrogen Spillover Effect at Ambient Temperature Observed Experimentally for the First Time

A group of scientists from Tohoku University, Japan experimentally demonstrated the hydrogen spillover effect of buckyball (a.k.a. fullerene or C60). They achieved this breakthrough using mass spectroscopy, and their findings were published recently in Chem. Commun.

Certain transition metal nanoparticles (e.g. Ru, Pt and Ni) can capture hydrogen molecules. The capture process generally involves three sequential steps. Firstly, hydrogen molecules split into hydrogen atoms on the metal surface. Secondly, the yielded hydrogen atoms migrate on the surface towards substrates under the metal nanoparticles and, finally, these atoms fix onto the substrates. The second step is termed the “spillover effect” (Figure 1a). Previous studies predicted that curved graphene sheets could enhance the hydrogen spillover effect at ambient temperatures, but solid experimental evidence has remained inadequate.

To gather evidence for this prediction, Nishihara et al. studied the material buckyball, a spherical carbon nanosphere that represents an extremely curved graphene sheet. The researchers selected ketjenblack (KB), a type of porous carbon sheet, as the substrate, and deposited Pt nanoparticles (1-3 nm in diameter) and buckyball molecules onto it (Figure 1b). They found that the Pt and buckyball-decorated KB stored a higher amount of hydrogen compared to the Pt-loaded KB. This observation indirectly confirmed the previous prediction, as hydrogen storage capacity may be improved by enhancing the spillover effect.

Figure 1. (a) A schematic illustration showing how a hydrogen molecule is split on Pt surface [process (1)] followed by the spillover effect [processes (2) and (2′)]. (b) A schematic illustration of the structure of Pt and buckyball-decorated KB. The inset panel displays two forms of hydrogen bound to the composite: the physically adsorbed di-hydrogen molecules, and the spillover hydrogen atoms anchored on the KB substrate and buckyballs.

 

The authors then sought time-of-flight mass spectroscopy to obtain more evidence. This spectroscopic technique is capable of identifying molecules with different mass to charge ratios (m/z). As shown in Figure 2, after treating the buckyball and Pt-loaded KB with deuterium molecules (D2), the spectrum (red) exhibited two additional peaks with m/z of ~723.5 and ~724.5 (highlighted by arrows in the figure) compared to those of the buckyball reference (black) and the buckyball and Pt-loaded KB prior to D2 dosage (blue). The authors ascribed these two new peaks to single D atom-adsorbed buckyballs with different amounts of carbon isotopes (12C and 13C). The presence of the two new peaks clearly showed that buckyballs could host hydrogen atoms to enhance the spillover effect. In addition, upon exposing the D-containing buckballs to air, both of the newly-merged peaks disappeared, suggesting that D atom adsorption was reversible.

Figure 2. The time-of-flight mass spectroscopy spectra of buckyball (black), Pt and buckyball-decorated KB before (blue) and after (red) exposure to D2, and after exposure to air (green). Pictures on the right show the molecular structure of a buckyball molecule and two deuterium-incorporated buckyball molecules (with different number of 13C isotope). Deuterium is used to avoid the interference from the 13C isotope.

This work could serve as a reference for future studies of the spillover effect induced by buckyballs interacting with other metal nanoparticles. The increasing availability of in-depth fundamental insight could refine our understanding of ambient-temperature hydrogen storage.

To find out more please read:

Enhanced Hydrogen Spillover to Fullerene at Ambient Temperature

Hirotomo Nishihara, Tomoya Simura and Takashi Kyotani

Chem. Commun. 2018, DOI: 10.1039/c8cc00265g

About the blogger:

Tianyu Liu obtained his Ph.D. (2017) in Physical Chemistry from University of California, Santa Cruz in United States. He is passionate about scientific communication to introduce cutting-edge research to both the general public and scientists with diverse research expertise. He is a blog writer for Chem. Commun. and Chem. Sci. More information about him can be found at http://liutianyuresearch.weebly.com/.

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Anchoring Arynes on Graphene with Microwave but No Solvents

Recently in ChemComm, an international team from Italy and Spain reported a non-conventional way to anchor arynes onto graphene surface using microwave. Their developed method is fast, efficient, mild and solvent-free.

Attaching functional groups onto graphene surface, i.e. functionalization, allows the physical and chemical properties of graphene to be fine-tuned, such as electrical conductivity and solubility. Conventional solvent-based functionalization strategies usually involve time-consuming reactions and tedious purification steps. The poor suspension stability of graphene in solvents, particularly in polar organic solvents, greatly hinders the overall functionalization efficiency. Therefore, establishing easy and solvent-free functionalization protocols for graphene is highly needed.

M. Prato, A. Criado and coworkers made a breakthrough in addressing this challenge by developing a microwave-assisted functionalization method. Their method to functionalize graphene consists of cycloaddition reactions between few-layer graphene (FLG) and arynes (Figure 1). These reactions proceed by mixing the dry powder of FLG and arylene anhydrides, the precursors of arynes, followed by rapid heating under microwave irradiation. The whole process is solvent-free and occurs within half a minute. It is also applicable to a variety of arynes (Figure 2).

Figure 1. The schematic illustration of the microwave-assisted functionalization of graphene with arynes. This process can be carried out within half a minute and is solvent-free.

Figure 2. A variety of arynes capable of being anchored on graphene surface. 1~6 represent the arylene anhydrides and f-G(7)~f-G(12) are corresponding arynes attached onto graphene.

The most unique feature of the demonstrated method is the dual role of FLG. In addition to being one of the reactants, FLG is capable of absorbing microwave energy, and enables its surface to rapidly reach high temperatures that significantly accelerate the cycloaddition reactions.

This microwave-assisted functionalization method shows great promise as a stepping stone for the fast and efficient modulation of graphene surface and subsequently, the performance of graphene-based electronics.

 

To find out more please read:

Microwave-Induced Covalent Functionalization of Few-Layer Graphene with Arynes Under Solvent-Free Conditions

V. Sulleiro, S. Quiroga, D. Peña, D. Pérez, E. Guitián, A. Criado and M. Prato

Chem. Commun. 2018, DOI: 10.1039/C7CC08676H

About the blogger:

Tianyu Liu obtained his Ph.D. (2017) in Physical Chemistry from University of California, Santa Cruz in United States. He is passionate about scientific communication to introduce cutting-edge research to both the general public and scientists with diverse research expertise. He is an online blog writer for Chem. Commun. and Chem. Sci. More information about him can be found at http://liutianyuresearch.weebly.com/.

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Single-Crystalline NiFe-Hydroxide Nanosheets for Catalyzing Oxygen Evolution

A group of scientists led by Prof. Shizhang Qiao has synthesized an oxygen evolution reaction (OER) catalyst combining the merit of low cost, excellent catalytic activity and long lifetime. This OER catalyst is composed of single-crystalline NiFe-hydroxide nanoflakes directly grown on nickel foams. The work has been published recently in ChemComm.

OER, the reaction of producing oxygen gas from water, is an indispensable component of electricity-generation devices using sustainable energy (e.g. fuel cells and photoelectrochemical water splitting cells). OER is usually the bottleneck limiting the overall energy conversion efficiency due to its sluggish kinetics and complex reaction pathways. As such, OER catalysts are needed to accelerate the OER reaction rate. Among the various OER catalysts, noble metal oxides stand out owing to their ultrahigh catalytic activity. However, the “shining” performance is dimmed by their high cost and short lifetime. Thus, obtaining alternatives with comparable OER catalytic activity as well as long-term stability is required to advance the utilisation of sustainable energy.

To address this challenge, the authors turned their attention to a low-cost transition metal, nickel. They developed a hydrothermal method using nickel foams to grow highly crystalline and near-vertically aligned NiFe-hydroxide nanosheets as OER catalysts (Figure 1a). The seamless integration between the hydroxide nanosheets and the nickel substrates reduces the contact resistance and facilitates interfacial electron transfer. The near-vertical orientation (Figure 1b) allows water molecules to fully contact the catalysts. Both of the characteristics render excellent OER catalytic activity. Additionally, the high crystallinity (Figure 1c) ensures the catalysts are robust enough to withstand extensive use without degradation in performance.

Figure 1. (a) The schematic illustration of the synthetic procedures of the NiFe-hydroxide [Fe-Ni(OH)2] nanosheets supported on nickel foams (NF). (b) The scanning electron microscopy image shows the near-vertically aligned nanosheets on a piece of nickel foam. (c) The transmission electron microscopy image reveals the crystallinity of the synthesized catalyst.

The NiFe-hydroxide nanosheets outperform most of the state-of-the-art OER catalysts, including those containing noble metal elements. Specifically, the nanosheets exhibit an onset potential of 1.497 V (Figure 2). The onset potential is a measure of the catalytic activity that equals the magnitude of potential required to yield a current density of 10 mA/cm2 (when appreciable amount of oxygen gas is evolved). Outstandingly, the onset potential of the NiFe-hydroxide is the smallest among the catalysts selected for comparison.

Figure 2. The polarisation curves of different OER catalysts. The onset potential is marked by the dotted line in the inset.

The catalytic activity is also highly stable, with no loss in performance after at least 100 h of measurement. Interestingly, the onset potential further shifts to a lower value of 1.465 V after 100 h. The authors attributed this observation to a “self-activation” process that involves the formation and accumulation of nickel oxyhydroxide (NiOOH) on the surface of the nanosheets.

The hydrothermal method demonstrated here could be used to synthesize other cost-effective crystalline catalysts to develop catalysts for reactions beyond OER, such as hydrogen evolution and carbon dioxide reduction.

To find out more please read:

Free-Standing Single-Crystalline NiFe-Hydroxide Nanoflake Arrays: A Self-Activated and Robust Electrocatalyst for Oxygen Evolution

Jinlong Liu, Yao Zheng, Zhenyu Wang, Zhouguang Lu, Anthony Vasileff and Shi-Zhang Qiao

Chem. Commun. 2017, DOI: 10.1039/c7cc08843d

About the blogger:

Tianyu Liu obtained his Ph.D. (2017) in Physical Chemistry from University of California, Santa Cruz in United States. He is passionate about scientific communication to introduce cutting-edge research to both the general public and scientists with diverse research expertise. He is a blog writer for Chem. Commun. and Chem. Sci. More information about him can be found at http://liutianyuresearch.weebly.com/.

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Binder-free Integration of Bismuth Nanoflakes onto Nickel Foams for Sodium-ion Batteries

A new type of bismuth-based electrode material for sodium-ion batteries has been synthesized. This electrode consists of bismuth metal nanoflakes seamlessly integrated onto nickel foams. The electrode contains no polymer binders, a crucial component required to retain the structural integrity of most battery electrodes. This binder-free feature improves the amount of charge being stored (i.e. capacity) at fast charging rates.

Sodium-ion batteries are attracting worldwide research efforts as electric energy storage devices, in addition to the prevalent lithium-ion batteries, due to the abundance of sodium. Similar to the preparation of other battery electrodes, fabricating sodium-ion battery electrodes generally requires binders, e.g. polyvinylidene fluoride (PVDF), to hold powdered electrode materials together and glue them to metal supporting substrates. However, the electrically insulating nature of the binders impedes fast electron transport between electrode materials and supporting substrates, consequently degrading the capacity of the batteries at fast charging rates.

Now in ChemComm, researchers from Nankai University & the Collaborative Innovation Center of Chemical Science and Engineering in China demonstrate a bismuth-based electrode material that does not involve a binder. This characteristic is realized by the in-situ growth of bismuth nanoflakes onto nickel foams through a solution-based replacement reaction (Figure 1). Because the nanoflakes grow directly from the nickel foam surface and firmly anchor onto nickel (Figure 2a), the resultant Bi/Ni composite can be directly used as an electrode. Specifically, the bismuth nanoflakes and nickel foam serve as the active material and supporting substrate, respectively.

The Bi/Ni composite exhibited excellent electrochemical performance. It achieved a high capacity of 377.1 mAh/g at a current density of 20 mA/g. Significantly, when the current density increased 100-fold, its capacity could still retain 206.4 mAh/g, which is more than half of the capacity obtained at 20 mA/g (Figure 2b). This outstanding capacity retention is a benefit of the binder-free characteristic that reduces the resistance of electron transport.

The authors then elucidated the working mechanism of the bismuth nanoflakes by in-situ Raman spectroscopy. They concluded that a two-step alloying process was responsible for the charge storage activity.

Figure 1. A schematic illustration showing the synthetic process of the binder-free Bi/Ni electrode. By inserting a piece of nickel foam into an ethylene glycol (EG) solution containing bismuth(III) nitrate, Bi3+ can replace Ni metal, be reduced to Bi metal and deposit on the Ni metal surface.

 

Figure 2. (a) A scanning electron microscopy image of the bismuth nanoflakes. (b) A plot showing the capacity of the Bi/Ni electrode at different current densities.

 

The successful synthesis of the binder-free electrode is expected to encourage future works on the design and synthesis of integrated electrode materials to advance the performance of sodium-ion batteries.

 

To find out more please read:

In situ Synthesis of Bi Nanoflakes on Ni Foam for Sodium-ion Batteries

Liubin Wang, Chenchen Wang, Fujun Li, Fangyi Cheng and Jun Chen

Chem. Commun. 2017, DOI: 10.1039/c7cc08341f

About the blogger:

Tianyu Liu obtained his Ph.D. in Physical Chemistry from University of California, Santa Cruz in United States. He is passionate about scientific communication to introduce cutting-edge research to both the general public and scientists with diverse research expertise. He is a web blog writer for Chem. Commun. and Chem. Sci. More information about him can be found at http://liutianyuresearch.weebly.com/.

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Commemorating Michael Faraday (1791-1867) – call for papers in physical chemistry

This year we are commemorating the 150th anniversary of the death of Michael Faraday, perhaps one of the most prolific and influential scientists who ever lived. His ground-breaking research into the relationship between electricity and magnetism ultimately led to the invention of the electric motor.

One of his most well-known creations, the Faraday cage, is the basis of MRI machines which are routinely used for a range of medical diagnoses. He also discovered benzene, pioneered research into nanotechnology, and gave his name to the Faraday Effect, Faraday’s Law, and the SI unit of capacitance, the farad.

At the Royal Society of Chemistry, we are honouring Michael Faraday with a special Chemical Communications web themed issue, highlighting key discoveries and developments in physical chemistry.

We encourage you to submit your best research to be included in this unique collection! More information about our article types can be found here. Submit at www.rsc.org/ChemComm by 31st July 2017! Please note that all submissions will be subject to peer review in accordance with the journal’s quality and standards. If you are interested in this opportunity, please email chemcomm-rsc@rsc.org

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Fluorescently finding a specific disease marker needle in a biological haystack

The early detection and monitoring of disease is a somewhat recent advancement in healthcare that offers the significant advantage of being able to treat an illness in its initial stages, rather than once it has already manifested itself in the patient. Such a feat requires, however, the ability to see very specific and characteristic disease markers in situ, not unlike the search for a needle in a haystack.
 
Luckily, with the advent of fluorescence (and other) imaging techniques, methods have been developed whereby, in combination with contrast agents that are able to interact with specific molecules in the body, cell chemistry and function can be observed with high sensitivity, and, more importantly, abnormalities in these processes noticed in real time.
 
The art and ultimate success of this fluorescence imaging comes from the design of the contrast agent employed – the probe should be able to selectively recognise and target the relevant disease marker reversibly and under biological conditions. A number of approaches currently exist that meet these requirements, one of which is the boronic acid recognition motif that is able to act as a molecular receptor for the 1,2- and 1,3-diols commonly expressed in carbohydrates and complex glycoproteins. Tony James and his team from the University of Bath, whose own research focuses on such use of boronic acid receptors in the detection of carbohydrates, have summarised the recent and exciting advances in this particular field of selective biological imaging.
 
The well-known and strong affinity of boronic acids for carbohydrates offers a convenient means of detecting commonly expressed markers in diseases including some cancers, as well as Alzheimer’s, autoimmune, and heart diseases. As such, the attachment of this relatively simple chemical moiety to fluorescent small molecular, polymeric or benzoxaborale-based probes offers a diagnostic tool that is able to detect, monitor, and aid in the personalised treatment of such significant and life-changing diseases.
 
This Feature Article convincingly highlights the impact that boronic acid-based fluorescence imaging will ultimately have on a range of important clinical and theranostic practices and their successes.
  
Read this hot ChemComm article in full:
X. Sun, W. Zhai, J. S. Fossey and T. D. James
Chem. Commun., 2016, 52, 3456–3469
DOI: 10.1039/C5CC08633G

About the Writer:
Anthea Blackburn is a guest Web Writer for Chemical Communications. Anthea hails from New Zealand, carried out her graduate studies in mechanostereochemistry under the guidance of Prof. Fraser Stoddart in the US, and has recently relocated to live in London. She is a recent addition to the Econic Technologies team, where she is working on the development of new catalysts for the environmentally beneficial preparation of polycarbonates from CO2.
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ChemComm Emerging Investigator Lectureship: Marina Kuimova

Dr Marina Kuimova (Imperial College London) was a recipient of the 2013 ChemComm Emerging Investigator Lectureship.

Marina has just completed her lectureship tour which took place in three locations in Europe from 7 – 13 July:

Kuimova

ChemComm Lectureship recipient Marina Kuimova giving her lecture at the IUPAC Symposium on Photochemistry

Our annual lectureship recognises an emerging scientist in the early stages of their independent academic career.

Professor Louise Berben (University of California Davis, USA) was the other recipient of the lectureship last year and we have just announced the 2014 winners – look out for further details of their lectureship tours soon.

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Mind the gap – Enhancing intercalation of luminescent aggregates

Particular molecules, which are not luminescent in solution, can luminesce intensely upon molecular aggregation; this is known as aggregation-induced emission (AIE). AIE luminogens are used widely as efficient electroluminescent materials, sensitive chemosensors, and as bioprobes. The main cause of the AIE effect is the restriction of intramolecular rotation. Therefore it can be promoted by introducing the molecules into inorganic materials with a rigid skeleton such as α-zirconium phosphate layers.

Jihong Yu and colleagues from Jilin University in China have published a method describing the intercalation of a quaternary tetraphenylethene (TPEN) cation, an AIE chromophore, into α-zirconium phosphate. At first glance, this does not seem to be too difficult a task– after all, the TPEN has two permanent positive charges on either end suitable to interact with the negatively charged phosphate layers. But, in this case, size does matter. The chromophore is almost three times larger than the distance between phosphate layers, more than a tight fit!

Stretching the layers of α-zirconium phosphate by preintercalation of butylamine before introduction of the chromophore

To overcome this problem, Yu and colleagues carried out a preintercalation step with butylamine before performing a cation exchange step to place the TPEN chromophore within the phosphate layers. Ultimately, they stretched the layer before putting the final molecule inside, just like you would stretch a pair of shoes in an effort to make them fit before placing your sensitive feet inside.

The intercalated product was found to be highly emissive in the blue region of the electromagnetic spectrum and was readily internalized by cells. The system also showed good biocompatibility, suggesting that it would make an excellent base for fluorescent labels in future biomedical imaging applications.

To read the details, check out the HOT Chem Comm article in full:

AIE cation functionalized layered zirconium phosphate nanoplatelets: ion-exchange intercalation and cell imaging

Dongdong Li, Chuanlong Miao, Xiaodan Wang, Xianghui Yu, Jihong Yu and Ruren Xu
Chem. Commun., 2013, 49, Accepted Manuscript
DOI: 10.1039/C3CC45041D

Iain Larmour is a guest web writer for ChemComm.  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 and art.

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Mechanochemistry: ChemComm web theme and Faraday Discussion 170 abstracts deadline 12 August

ChemComm Mechanochemistry web collection

We are delighted to present our ChemComm web themed issue on Mechanochemistry: fundamentals and applications in synthesis, guest edited by Stuart James (Queen’s University Belfast, UK) and Tomislav Friščić (McGill University, Canada).  Check out this special online collection now!

C3CC90136J

Faraday Discussion 170 on Mechanochemistry– deadline for oral abstracts 12 August 2013

We also invite you to submit your oral abstract for Faraday Discussion 170– Mechanochemistry: From Functional Solids to Single Molecules by Monday, 12 August 2013.  Stuart and Tomislav co-chair the FD170 Scientific Committee; they are joined by Jon Steed, James Mack, Elena Boldyreva and Carsten Bolm.

FD170banner

Submit your abstract now and register to secure your place at this exciting event!

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A cloak of many carbons

Catalysts can be exceedingly useful in the real world, from treating our car’s exhaust fumes to creating fertilisers.  There are many ways to make catalysts and even multiple ways to make the same catalyst.  The path that you choose to a catalyst can have a significant impact on the quality of the end product.

Eloy del Rio and team from the Structure and Chemistry of Nanomaterials group at the University of Cadiz in Spain have investigated ceria-based oxide-supported gold catalysts for carbon monoxide oxidation.  The routine for depositing the metal phase onto the oxide support and the subsequent catalyst activation step can ultimately affect the activity of the catalyst.  Catalysts prepared by deposition-precipitation with urea followed by activation under oxidising conditions result in significantly more activity than those prepared under reducing conditions.

Variation in catalyst activity under oxidising and reducing activation protocols.

This had previously been observed by others, but the reason for the difference was never discussed.  The authors set out to find out why the activity differed.  They used a suite of nano-analytical and nano-structural techniques to probe the catalysts, finding that the catalyst prepared under reducing conditions had a coat of amorphous carbon which severely hampered the catalyst activity.  This could be removed by a re-oxidation treatment that burnt away the carbon layer and produced an active catalyst similar to the one produced under oxidising conditions.

The precipitating agent used in the synthesis can also influence the resulting activities of catalysts prepared via the deposition-precipitation method.  No difference between oxidising and reducing activations is observed when sodium carbonate is used in place of urea.

To read the details, check out the ChemComm article in full:

Dramatic effect of redox pre-treatments on the CO oxidation activity of Au/Ce0.50Tb0.12Zr0.38O2-x catalysts prepared by deposition-precipitation with urea: a nano-analytical and nano-structural study
E. del Rio, M. López-Haro, J.M. Cies, J.J. Delgado, J.J. Calvino, S. Trasobares, G. Blanco, M.A. Cauqui and S. Bernal
Chem. Commun., 2013, 49, Accepted Manuscript
DOI: 10.1039/C3CC42051e

Iain Larmour is a guest web writer for ChemComm.  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 and art.

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