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Spectroscopy

Analytik reports on use of the CPS Disc
Centrifuge system for measurement of size
and density of nanoparticles by the Nanoanalysis
Group at the National Physical Laboratory

Analytik, leading suppliers of innovative analytical instrumentation, report on use of the CPS Disc Centrifuge for ultra-high resolution nanoparticle size analysis by the Nanoanalysis Group of the National Physical Laboratory.

The National Physical Laboratory (NPL), the United Kingdom's National Measurement Institute, is well equipped with many means to characterise the size of nanoparticles1. These are complementary and are used in concert or alone depending on the type of materials being studied. Every particle sizing technique is based on a different physical principle and therefore measures a slightly different "size" of the nanoparticle. Take, for example, a gold nanoparticle stabilised with citrate molecules. Dynamic Light Scattering, DLS, will measure the hydrodynamic radius; that is the gold core, the molecular coating and every molecule of solvent that moves with the core. In contrast, transmission electron microscopy, TEM, measures the size of the metallic core, thus providing a size of the nanoparticle that is smaller than that measured by DLS.

Picture 1. Dr Caterina Minelli of the NPL's Nanoanalysis Group using the CPS Disc Centrifuge technique for nanoparticle size and density characterisation.

Picture 2. CPS size distribution of polystyrene nanoparticles (NPs, blue ◊) and the same NPs functionalised with Immunoglobulin G (IgG) antibodies (red ◊). The high resolution size distribution of the functionalised particles allows identification and quantification of monodisperse NPs and those agglomerated in doublets, triples or larger aggregates.

The Group also uses the CPS Disc Centrifuge system from Analytik. This technique is based on differential centrifugal sedimentation. Describing this technique, Dr Caterina Minelli says: "The CPS technique is very precise and produces particle size distributions with extremely high resolution. This means that when we attach antibodies to the surface of a nanoparticle, for example, we are able to identify and quantify not only the main population of well functionalised particles, but also the fraction of undesired particles that aggregate in doublets, triplets or larger aggregates. The CPS instrument thus provides us with a means to assess the quality of a surface functionalisation protocol and supports its improvement and refinement."

Continuing, Dr Minelli says: "Another advantage of the CPS technique is that in combination with other techniques, or with careful experiments, we can measure both the size and the density of particles. This is because the instrument measures the particle sedimentation time through a medium, which depends on both the particle size and the density. If the size of the particle is known, for example by measuring it with an independent technique, the CPS can provide a direct measurement of the particle density. When we modify the surface of a nanoparticle, for example by coating it with molecules such as proteins, we change both its size and its effective average density. The ability to measure the change in the particle density means we have a tool to characterise the molecular coating surrounding the nanoparticles. This approach is useful to study engineered nanoparticles used in biosensing. Another application involves the study of how protein corona forms at the nanoparticles' surface as they enter a biological fluid such as blood or urine. The entity of the protein corona will determine the fate of the nanoparticles and has strong implications for nanoparticle toxicity, for example."

With a wide variety of materials and potential users for making routine analytical particle size measurements, the CPS is particularly popular because of its versatility and ease of use. From a research perspective, the main use of the CPS is to optimise the highly engineered biomolecular coating of nanoparticles used in biosensing systems or other medical applications. This experience enables the NPL's Nanoanalysis Group to offer contract analysis to external clients. Further details are available at http://www.npl.co.uk/science-technology/surface-and-nanoanalysis/services

To find out more about CPS' disc centrifuge nanoparticle characterisation systems, visit: http://www.analytik.co.uk/nanoparticle-size-analysis.htm Reference: (1) "Emerging Techniques for Submicrometer Particle Sizing Applied to Stüber Silica" by Nia C. Bell, Caterina Minelli et al.,
Langmuir 28 (2012) 10860; (2) "Quantitation of IgG protein adsorption to gold nanoparticles using particle size measurement" by Nia C. Bell, Caterina Minelli and Alexander G. Shard, Analytical Methods 5 (2013) 4591. 

New GL Optic SPECTIS 5.0 touch,
a compact spectrometer that offers
laboratory-grade accuracy and resolution

Analytik, partner with German company, GL Optic, for the supply of handheld and laboratory-based spectroradiometers and integrating spheres for use in both quality control and research applications for the growing lighting marketplace. Today, Analytik announces the release of the new SPECTIS 5.0 touch spectrometer for quick and accurate testing of conventional, LED and other solid-state lighting equipment in the field and in production.

The new GL SPECTIS 5.0 from GL Optic is a compact portable spectrometer running an Android operating system for laboratory-grade characterisation of light sources. Suitable for measuring the spectral power distribution of luminaires, flat panel displays, diffusely reflecting surfaces and individual LEDs, as well as for photobiological safety testing and characterisation of solid-state lighting products, the new instrument can be deployed in the field with no loss of accuracy or resolution.

The GL Spectis 5.0 touch measures just 111mm x 210mm x 58mm and weighs only 1.5kg. It is equipped with a full-colour 3.2" 240 x 320 touch-screen display. The user can configure test set-ups and see measurement results even without a PC connection. For PC-controlled operations using the optional GL SPECTROSOFT software, the instrument can connect wirelessly via Wi-Fi, Bluetooth or with a standard USB cable interface.

While the new instrument has a convenient small size, GL Optic has packed a laboratory instrument's capability inside the unit. It boasts a physical resolution of 0.5nm and FWHM optical resolution of 2.5nm over a broad spectral range of 200-1050nm. Over this entire range, the instrument's spectral radiometric accuracy is rated to within ±4%. Colour measurements are also highly accurate: in the visible portion of the light spectrum, the uncertainty of colour co-ordinate (x, y) measurements is just 0.0015.

Measurements that may be viewed on the touch-screen display include full spectral power distribution profiles, CIE chromaticity charts, colour co-ordinates, CCT and CRI values (Ra and R1-R14) and the peak wavelength value. To provide accurate measurements in the field, the GL Spectis 5.0 touch implements GL Optic's proprietary Optical Stray Light Reduction (OSR) technology giving excellent signal-to-noise performance and more accurate results. Automatic baseline correction with the integrated temperature sensor ensures high measurement stability and performance over the operating temperature range of 5-35°C. This makes the spectrometer ideal for measurements to evaluate viewing conditions in accordance with ISO 3664, testing compliance with the eco-design requirements of EU standard 1194/2012, luminaire evaluation under LM-79 testing and photobiological safety testing of UV-emitting light sources.

The instrument is also compatible with a wide range of optical accessories, including integrating spheres and optical probes. It detects which optical probe is attached and automatically applies the correct calibration file in the software, so switching probes/interfaces is quick and flexible.

Mikolaj Przybyla, brand director of GL Optic, said: 'A number of advanced technologies have been combined in the GL Spectis 5.0 to produce a unique portable instrument that stands comparison, in terms of performance, with most bench-top spectrometers found in labs today. At last users can enjoy the convenience of using a compact instrument without having to compromise on measurement quality.'

For further information, view website: www.analytik.co.uk/dedicated-light-measurement-and-testing.htm 

Analytic's ASD portable FieldSpec® 4 spectroradiometer
is being used at the Fitzwilliam Museum for pigment analysis

Analytik, leading suppliers of innovative analytical instrumentation, has supplied an ASD portable FieldSpec® 4 spectroradiometer to the Fitzwilliam Museum in Cambridge where the researchers are performing pigment analysis of illuminated manuscripts.

Dr Paola Ricciardi is a research associate in the Department of Manuscripts and Printed Books at the Fitzwilliam Museum in Cambridge. Her work is part of the MINIARE project, focusing on Manuscript Illumination: Non-Invasive Analysis, Research & Expertise. MINIARE is a new interdisciplinary collaboration between the Fitzwilliam Museum and the University of Cambridge's Departments of Chemistry, Physics, Art History and History and Philosophy of Science. It aims at using a combination of advanced scientific methods for the study of illuminated manuscripts, in order to inform interdisciplinary research and finally provide details of the artistic, cultural, political, social and economic environments in which the manuscripts were created, taking into account trade routes, social and international mobility, intellectual and technological developments. MINIARE brings the sciences, arts and humanities together in Cambridge in unprecedented and exciting ways. The long-term goal is to establish a unique, interdisciplinary research centre that will foster collaboration with research institutions worldwide, training a new generation of scholars that will bridge the divide between the arts and the sciences.

Dr Paola Ricciardi uses the ASD FieldSpec 4 spectroradiometer at the Fitzwilliam Museum, Cambridge, where the researchers are performing pigment analysis of illuminated manuscripts.

During April and May 2012, Dr Ricciardi and Anuradha Pallipurath (Department of Chemistry) from the MINIARE team used an ASD FieldSpec 4 instrument to characterise both inorganic and organic materials (pigments and binders) on a number of illuminated manuscripts. This spectroradiometer has an extended operating range (350-2500 nm) and this is the key to the success of their work. It is the inclusion of the NIR region (1001-2500 nm) that allows for the analysis of some of the vibrational overtones and band combinations due to functional groups such as hydroxyls, carbonates, and potentially methylenic and amide groups associated with paint binders. For example, one can easily separate green malachite from mixtures of organic yellows and blue azurite. Both being copper carbonates, malachite and azurite are completely indistinguishable by X-ray fluorescence but the latter shows characteristic absorption bands at 1495, 2285, and 2350 nm.

Speaking of the FieldSpec 4 spectroradiometer, Dr Ricciardi said that "the technical specifications including its high sensitivity and high spectral resolution make it the optimal tool to investigate thin and often complex paint layers. The rapidity of acquisition in addition to the instrument's compactness and portability allow surveying a large number of objects directly in exhibition Galleries or storage rooms. It may also yield a substantial comprehensive data set in a short period of time. This allows carrying out large-scale surveys, acquiring spectra on both test panels and works of art, which then can be interpreted and used to both answer some of the art historical questions raised in the initial phase of the research and to inform subsequent phases of the project, during which the characterisation of the materials can be completed, when needed, using supplementary analytical methods such as Raman spectroscopy, XRF, and others."

More information on this work may be found on the MINIARE web site: http://www.miniare.org The work was carried out with the benefit of a Goetz Instrument Support Program award which is co-sponsored by ASD Inc., and the Geoscience & Remote Sensing Society.

More information may be found at: www.asdi.com/service-and-support/goetz-instrument-support-program ASD's range of instrumentation is available in the UK & Ireland from Analytik.

For further information, view website: www.analytik.co.uk/portable-remote-sensing-spectroradiometry.htm

To find out more about the ASD portable FieldSpec® 4 spectroradiometer, also view website: http://www.analytik.co.uk 

GL Optic's SPECTIS 1.0 touch spectrometer: Features
include high sensitivity and innovative noise reduction

Analytik, leading suppliers of innovative analytical instrumentation to the UK and Ireland, partner with German company, GL Optic, for the supply of handheld and laboratory based spectroradiometers and integrating spheres for use in both quality control and research applications for the growing lighting marketplace. Here, Analytik announces the first Android-based mobile smart spectrometer for measurement of colour co-ordinates, correlated colour temperature, colour rendering index, luminous flux and many other important lighting parameters.

The new GL SPECTIS 1.0 touch from GL Optic is the first mobile spectrometer using an Android-operating system which offers the latest communication technologies such as WiFi and BlueTooth. This unique device offers improved functionality and many new features. The GL SPECTIS 1.0 touch integrates performance of a high end spectrophotometer into a handheld, intuitive, touch screen device, making it the world's first intelligent "smart" spectrometer. The instrument does not require a computer in order to take measurements and immediately shows critical data on the colour touch display interface. Full spectral profile, chromaticity charts and all lighting parameters can easily be displayed. A temperature sensor installed on the electronic board monitors change in temperature and automatically compensates providing excellent measurement stability. Battery life is up to 6 hours and built-in data storage can save up to 1000 measurements.

The GL SPECTIS 1.0 touch is perfectly suited for spectral assessment of light sources in operational, quality and development areas. Applications include precise measurement of complete lighting installations, such as exterior LED lights for street lighting and daily quality control of LED production. The spectrometer measures quickly and reliably - in the production facility, during the maintenance of lighting installations or for certification of light sources such as LED retrofits for incandescent lamps.  For further information, view website: www.analytik.co.uk/dedicated-light-measurement-and-testing.htm 
Refer to page 282

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