Archive for the ‘Analytical’ Category

Gold nanoparticles reveal fingerprints

Gold nanoparticles capped with mercaptocarboxylic acids, followed by silver precipitation, have been used to develop latent fingerprints on paper as high quality negative images. Scientists writing in the journal ChemComm say that the effect stems from hydrogen bonding between the carboxylic group and the paper cellulose.

Recovering fingerprints from paper is a common task for forensic scientists, but often the developed marks are faint. A common approach, therefore, is to use a developing agent that sticks to the clean paper substrate, rather than the fingerprint itself, yielding a reversed image.

The technique described in this study is much less affected by sweat composition, and could improve the yield of latent fingerprints.

Read the ‘HOT’ ChemComm article today for free:

A novel approach to fingerprint visualization on paper using nanotechnology: reversing the appearance by tailoring the gold nanoparticles’ capping ligands
Sanaa Shenawi , Nimer Jaber , Joseph Almog and Daniel Mandler
Chem. Commun., 2013, DOI: 10.1039/C3CC41610K

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Lewis acidity of metal ions investigated in the gas phase

In aqueous solutions metal ions can promote acidity via the hydrolysis reaction. This is measured by a hydrolysis constant, which has previously been correlated to the ratio of the ion’s charge to size. Unfortunately lead and tin stubbornly refuse to fit this correlation; additional factors must be at work.

Anthony Stace and team investigated further by studying the minimum number of water molecules needed to stabilise a dication complex in the gas phase against spontaneous hydrolysis (called Coulomb fission in the gas phase). They found an extraordinarily good correlation between the number of water molecules required and the metal ion’s hydrolysis constant in aqueous solution.

What about those stubborn dications, lead and tin? They fit within the trend, requiring a surprising 11 and 26 water molecules to stabilise them respectively. This work suggests that Lewis acidity of metal ions is determined, in part, by the requirement that the ions remain fully solvated.

Plot of acidity constant against minimum number of water molecules required to stabilise the complex against Coulomb fission.

To find out more, download the ChemComm article today.

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Personal glucose sensors can be adapted to detect cancer too

Personal glucose sensors (PGS) can be used to detect cancer, say Chinese scientists.

The team loaded magnetic beads with invertase (an enzyme that catalyses the hydrolysis of sucrose to glucose) and an antibody. The beads acted as a label for a lung cancer biomarker that had been captured on an antibody-coated ELISA plate. By monitoring the production of glucose from sucrose with a PGS, they could indirectly measure the amount of the biomarker down to the sub-nanogram per millilitre level.

Graphical Abstract

 

Link to journal article
Personal glucose sensor for point-of-care early cancer diagnosis
Jiao Su, Jin Xu, Ying Chen, Yun Xiang, Ruo Yuan and Yaqin Cha
Chem. Commun., 2012, Accepted Manuscript, DOI: 10.1039/C2CC32729E

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Nanoscopic electrochemical cells probe forests

3D carbon nanotube forests are of particular interest in the electrochemical arenas of sensing and energy applications. Some researchers have suggested that it is necessary to use open-ended carbon nanotubes and carry out a pre-treatment or activation step to support fast electrochemistry, but is this always the case?

Patrick Unwin and co-workers set out to investigate. They prepared carbon nanotube forests using a chemical vapour deposition growth method. To probe the local electrochemical response of the forests, they used a nanoscopic double barrelled pipette tip, filled with supporting electrolyte and redox species. This allowed the team to interrogate the sidewalls and closed ends of the nanotubes that made up the forest with high spatial resolution.

Both sidewalls and the closed tube ends were capable of fast electron transfer proving that single walled carbon nanotubes do not require open ends for fast electrochemistry with outer sphere redox couples. This overturns the current consensus, based on averaged macro-sized measurements, that open ends dominate nanotube forest electrochemistry.

Without the requirement for pre-treatment or activation, electrochemical nanotube forest applications will be easier to achieve.

To find out more, download the ChemComm article today.

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Optical chemosensors for sensing explosives

Peroxide-based explosives, such as triacetone triperoxide (TATP), have been increasingly used in criminal activities as they can be easily obtained and are highly sensitive (TATP has 88% the explosive equivalence of TNT). However, detecting TATP is not easy, despite its considerable vapour pressure at room temperature (7.87Pa), This is mainly because of its lack of nitro- or aromatic-groups, which could be revealed in UV absorbance or fluorescence spectra.

Here, researchers in China have demonstrated a new strategy to detect explosive peroxide vapor via deboronation reaction induced fluorescence quenching with good sensitivity (the detection limit of TATP vapour was estimated to be ~0.5ppm), selectivity and fast response.


 

Link to journal article
Highly Efficient Fluorescent Sensor of Explosive Peroxide Vapor via ZnO Nanorod Array Catalyzed Deboronation of Pyrenyl borate

C He et al
Chem. Commun.,
2012, DOI: 10.1039/c2cc31386c

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Ambient pressure XPS on the cheap

X-ray photoelectron spectroscopy (XPS) is capable of characterising the surface composition, oxidation state and electron state of materials. Unfortunately, it uses electrons and so common XPS machines must work at vacuum pressures. But how could you use XPS under ambient pressure?

One option would be to use public synchrotron facilities but access is through proposal review and available time is restricted so it is not feasible for day-to-day studies. Another option would be to follow the lead of Franklin Tao and build an inexpensive, ambient pressure XPS machine in-house.

Such a machine is ideal for catalytic studies. Previously scientists investigated catalysts with conventional vacuum XPS before and after experiments. Tao’s machine enables him to investigate catalyst surface changes during reaction conditions, something that required synchrotron facilities until now. The machine’s novel reaction cell allows XPS measurements to be carried out at up to 25-50 Torr using an inexpensive bench top X-ray source.

external view of the reaction cell
external view of the reaction cell

In addition to the ambient pressure XPS functionality, an on-line mass spectrometer allows correlation between catalytic performance and surface chemistry. Tao has demonstrated this novel machine by investigating the oxidation and reduction of ceria under real reaction conditions.

With day-to-day ambient pressure XPS now within reach of every research group, catalytic studies under reaction conditions have received a significant boost.

To find out more, download the ChemComm article today.

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Cheap and non-toxic porphyrins for detecting cells deep within the body

Near-infrared fluorescent imaging can be used for rapid and sensitive detection of cells deep within the body. However, common NIR dyes and quantum dots are expensive and/or toxic.

Porphyrins are economical fluorescent dyes, but their emission and excitation wavelengths are shorter than the NIR region and they can be toxic and poorly water-soluble. Scientists in Japan have made silica–porphyrin hybrid nanotubes that have no acute toxicity and higher water solubility compared to porphyrin. They used them to label macrophages, injected them into mice and tracked their distribution by fluorescence imaging with good results.

c2cc17444h

Link to journal article
Silica/Porphyrin Hybrid Nanotubes for In Vivo Cell Tracking by Near-Infrared Fluorescence Imaging
K Hayashi, M Nakamura and K Ishimura
Chem. Commun., 2012, DOI: 10.1039/c2cc17444h

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Free analytical content in ChemComm

ChemComm-RSC Prizes & Awards Symposium

The ChemComm–RSC Prizes & Awards Symposium takes place at Imperial College London on 22nd February 2012 with the theme of (bio)analytical science.

This is ChemComm‘s first UK-based symposium and to celebrate we’ve made some of our best analytical content free to access for a limited period.

We hope you enjoy these articles – but don’t delay! Free access only runs until 29th February.

Perspectives in imaging using mass spectrometry
Allison L. Dill, Livia S. Eberlin, Demian R. Ifa and R. Graham Cooks
Chem. Commun., 2011, 47, 2741-2746

Metal binding to a zinc-finger peptide: a comparison between solution and the gas phase
Yana Berezovskaya, Craig T. Armstrong, Aimee L. Boyle, Massimiliano Porrini, Derek N. Woolfson and Perdita E. Barran
Chem. Commun., 2011, 47, 412-414

Spectroscopic analysis of immobilised redox enzymes under direct electrochemical control
Philip A. Ash and Kylie A. Vincent
Chem. Commun., 2012, 48, 1400-1409

Fluorescent dye-doped silica nanoparticles: new tools for bioapplications
Se Won Bae, Weihong Tan and Jong-In Hong
Chem. Commun., 2012, 48, 2270-2282

Ultrasensitive fluorescence-based methods for nucleic acid detection: towards amplification-free genetic analysis
Rohan T. Ranasinghe and Tom Brown
Chem. Commun., 2011, 47, 3717-3735

An optimized isotopic labelling strategy of isoleucine-γ2 methyl groups for solution NMR studies of high molecular weight proteins
Isabel Ayala, Olivier Hamelin, Carlos Amero, Ombeline Pessey, Michael J. Plevin, Pierre Gans and Jérôme Boisbouvier
Chem. Commun., 2012, 48, 1434-1436

Nucleobase recognition at alkaline pH and apparent pKa of single DNA bases immobilised within a biological nanopore
Lorenzo Franceschini, Ellina Mikhailova, Hagan Bayley and Giovanni Maglia
Chem. Commun., 2012, 48, 1520-1522

FRET detection of amyloid β-peptide oligomerization using a fluorescent protein probe presenting a pseudo-amyloid structure
Tsuyoshi Takahashi and Hisakazu Mihara
Chem. Commun., 2012, 48, 1568-1570

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Joint ChemComm–RSC Prizes and Awards Symposium in London

We are delighted to announce the forthcoming ChemComm–RSC Prizes & Awards Symposium in association with the RSC Analytical Division.

Date: Wednesday 22nd February 2012
Location: Imperial College London, UK
Time: 1300-1800

The purpose of this event is to bring together scientists in a stimulating and friendly environment to recognise the achievements of individuals in advancing the chemical sciences and also to foster collaborations. The symposium will appeal to academic and industrial scientists with an interest in analytical science, protein structure and interactions, and biosensors. Attendance at the symposium is FREE OF CHARGE and student participation is strongly encouraged.

The following distinguished scientists have agreed to speak:

For further details and to register your interest, please contact Anne Horan.

***
The closing date for RSC Prizes and Awards 2012 is 15th January 2012. Find out more >
***

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One nanoparticle, two nanoparticles, three nanoparticles, four!

Nanoparticles might be small but they frequent the pages of many a journal due to the ongoing boom in nanotechnology research. Whilst they are useful in a myriad of fields, it is still difficult to directly characterise these extraordinarily small entities. King among the visualisation techniques is electron microscopy but this often requires the isolation of the sample on a support – hardly sufficient for analysing a dynamic sample in solution! Dynamic light scattering is another potential technique but finds limitations when it comes to much smaller nanoparticle sizes.

Ideally, you want to be able to count and size individual nanoparticles at a rate which produces reliable statistics. To address this challenge, Richard Compton and his team, including Neil Rees and Yi-ge Zhou who conducted the experiments alongside Jeseelan Pillay, Robert Tshikhudo and Sibulelo Vilakazi from Mintek, Randburg, have used anodic particle coulometry (APC) to measure gold nanoparticle collisions with a glassy carbon microelectrode and thus count and size individual nanoparticles.

With the electrode potential set above +1.0 V, they were able to record oxidative Faradaic transients from nanoparticle collisions and calculate an average nanoparticle radius which compared extremely well to the radius obtained from scanning electron microscopy measurements. They were also able to observe nanoparticle aggregation, which holds great promise for monitoring dynamic aggregation reactions.

It shouldn’t be long before this technique is routinely used to gain more information on all sizes of metallic nanoparticles which are currently being used in a variety of applications.

Read the ChemComm article by Compton and team for more.

Posted on behalf of Iain Larmour, web science writer for ChemComm.

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