Book List. Books Under $10 That Build Character. Grades PreK - 8 Orson Scott Card's The Last Shadow is the long-awaited conclusion to both the original Ender series and the Ender's Shadow series, as the children of Ender and Bean solve the great problem of the Ender Universe—the deadly virus they call the descolada, which is incurable and will kill all of humanity if it is allowed to escape from Lusitania. One planet Characterization techniques for nanoparticles: comparison and complementarity upon studying nanoparticle properties. Stefanos Mourdikoudis ab, Roger M. Pallares ab and Nguyen T. K. Thanh * ab a Biophysics Group, Department of Physics and Astronomy,
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Stefanos Mourdikoudis abRoger M. Pallares ab and Nguyen T. E-mail: ntk. thanh ucl. uk b UCL Healthcare Biomagnetic and Nanomaterials Laboratories, 21 Albemarle Street, London W1S 4BS, UK, s gilles robust description and matching of images phd thesis. Nanostructures have attracted huge interest as a rapidly growing class of materials for many applications.
Several techniques have been used to characterize the size, crystal structure, elemental composition and a variety of other physical properties of nanoparticles. In several cases, there are physical properties that can be evaluated by more than one technique.
Different strengths and limitations of each technique complicate the choice of the most suitable method, while often a combinatorial characterization approach is needed.
In addition, given that the significance of nanoparticles in basic research and applications is constantly increasing, it is necessary that researchers from separate fields overcome the challenges in the reproducible and reliable characterization of nanomaterials, after their synthesis and further process e.
annealing stages. The principal objective of this review is to summarize the present knowledge on the use, advances, advantages and weaknesses of a large number of experimental techniques that are available for the characterization of nanoparticles.
We describe the main characteristics of the techniques and their operation principles and we give various examples of their use, presenting them in a comparative mode, when possible, in relation to the property studied in each case. Dr Stefanos Mourdikoudis is a chemical engineer who obtained his PhD degree from the Department of Physics, Aristotle University of Thessaloniki in Greece in Apart from his native country, he also worked in post-doctoral projects in France and Spain.
Currently he is working at the University College London UCL s gilles robust description and matching of images phd thesis a research associate.
His current research activity involves mostly work on the synthesis and characterization of magnetic nanoparticles. The variety of nanostructures he prepares are either directed s gilles robust description and matching of images phd thesis specific applications or simply inspired from curiosity to explore new protocols and characterize the resulting products.
Roger M. Pallares received his BSc and MSc degrees in chemistry from the Ramon Llull University Barcelona, Spain in andrespectively. After a year working on the growth of 2D nanomaterials at NTT Basic Research Laboratories Atsugi, Japanhe started a joint doctoral program between the University College London UCL, London, UK and the Agency for Science, Technology and Research Singaporeobtaining a PhD in materials science from UCL in He is currently a postdoctoral fellow at Northwestern University Evanston, IL.
His research interests focus on the use of nanomaterials for biomedical applications. ukheld a prestigious Royal Society University Research Fellowship — She was appointed a full professor in nanomaterials in at the Biophysics Group, Department of Physics and Astronomy, University College London, UK.
She leads a very dynamic group conducting cutting edge interdisciplinary and innovative research on the design and synthesis of nanomaterials for biomedical applications from diagnostics to treatment of diseases such as cancer.
She has published nearly peer reviewed journal articles and book chapters with over citations so far. She has been a visiting professor at various universities in France, Japan, China and Singapore. She has been an invited speaker at over institutes and scientific meetings.
Herein we describe extensively the use of different methods for the characterization of NPs. These techniques are sometimes exclusive for the study of a particular property, while in other cases they are combined. The techniques are analysed in depth, despite their big number presented herein.
There are microscopy-based techniques e. TEM, HRTEM, and AFM — the full names of the techniques are provided later in the text, when s gilles robust description and matching of images phd thesis each one of themwhich provide information on the size, morphology and crystal structure of the nanomaterials.
Other techniques are specialized for certain groups of materials, such as the magnetic techniques. Examples of these techniques are SQUID, VSM, FMR, and XMCD. Many other techniques provide further information on the structure, elemental composition, optical properties and other common and more specific physical properties of the nanoparticle samples.
Examples of these techniques include X-ray, spectroscopy and scattering techniques. This review is organized in different sections, which will present numerous distinct characterization techniques for NPs in relation to the properties studied see Tables 1 and 2.
The sections are categorized according to the different technique groups, as described above. Upadhyay et al. determined the average crystallite size of magnetite NPs using X-ray line broadening, and it was found to be in the range of 9—53 nm. On the contrary, the TEM-deduced size was higher than that calculated using XRD, for samples with very large particles; in fact, when the particle size is bigger than 50 nm, there are more than one crystal boundary on their surface. XRD cannot distinguish between the two boundaries; therefore the actual TEM size of certain samples can be in reality bigger than the 50—55 nm calculated by the Scherrer formula.
Dai and co-workers prepared ultra-small Au NPs which were very likely to be more developed along the 〈〉 direction rather than the 〈〉 one as the peak corresponding to the former direction was much more intense in their XRD measurement.
cubes, plates, and rodsthe relative intensities between the different XRD peaks varied in relation to the particle shape. X-ray absorption spectroscopy XAS includes both extended X-ray absorption fine structure EXAFS and X- ray absorption near edge structure XANES, also known as NEXAFS.
XAS measures the X-ray absorption coefficient of a material as a function of energy. Each element has a set of characteristic absorption edges corresponding to the different binding energies of its electrons, giving XAS element selectivity. As a highly sensitive technique, EXAFS is a convenient way to identify the chemical state of species s gilles robust description and matching of images phd thesis may occur even in very low concentrations.
Synchrotrons are usually needed to acquire XAS spectra; therefore it is not a routine or readily available technique. Pugsley et al. used in situ XAS to examine the kinetics and mechanism of formation of germanium NPs upon the reaction of Mg 2 Ge and GeCl 4.
The analysis of EXAFS yielded a first-neighbour Ge—Ge distance of 2. Moreover, Chen et al. applied in situ EXAFS for the inspection of structural changes around germanium atoms in GeO 2 NPs. Surprisingly, they noticed that at high temperature GeS 2 was formed as a product of the complete transformation of germanium dioxide, in the presence of a sulfur source. The XANES and EXAFS analyses of the atomic structure and electronic properties of these NPs showed that the sulfidation of Pd clusters caused by the capping thiol molecules took place not only on the surface but also in the bulk.
Energy dispersive EXAFS helps to determine both structural and kinetic parameters in supported metal catalysts for reactions occurring on a timescale of a few seconds, s gilles robust description and matching of images phd thesis. Such a fast operation enables the aforementioned technique to be used at temperatures higher than °C, which would hinder the use of surface enhanced Raman spectroscopy SERSas the latter technique is not that fast under such conditions.
Even on a timescale of tens of milliseconds, energy dispersive EXAFS can be used as a quantitatively suitable in situ probe of the dynamics of quick phase change in supported nanoparticulate metal catalysts.
EXAFS is one of the most convenient techniques for the structural analysis of NPs with sizes lower than 10 nm. It possesses a high spatial resolution and provides information on the nearest environment of an atom in a compound in the absence of long-range order.
The parameters derived in that study were partial coordination numbers, interatomic distances and Debye—Waller factors. In another study, Zhang and colleagues coated γ-Fe 2 O 3 NPs with sodium dodecylbenzene sulphonate DBSstearic acid and hexadecyltrimethylammonium bromide CTAB surfactants by the microemulsion method. The role of the surfactants was investigated through EXAFS analysis and it was found that all samples had a tendency to extend the Fe—O bond length.
All these molecules possess large spatial resistance, with the CTAB molecule having the largest one. The lattice distortion and disorder at the interfaces could play a significant role in hindering the fast nanoparticle growth. The authors state the importance of EXAFS for the acquisition of information concerning the coordination number, s gilles robust description and matching of images phd thesis, the nature of the scattering atoms surrounding the absorbing atom, the interatomic distance between absorbing and backscattering atoms, as well as the Debye—Waller factor, which is related to a disorder because of static displacements and thermal vibrations.
The possible phase shifts during the EXAFS process and interference effects from different scattering channels cause the modification of the position of the peaks in the FT, which become no longer identical to the geometric distance between the backscattering atoms and the absorbing atom. As an alternative method aiming to tackle the drawbacks of the FT approach, the wavelet transform WT has been proposed, as reported by C.
Schmitz Antoniak. More details of that approach can be found in ref. EXAFS can also be used to study copper cation inversion in CuFe 2 O 4 as a function of saturation magnetization. XANES is more helpful to determine the oxidation states, vacant orbitals, electronic configuration and site symmetry of the absorbing atom.
XANES measurements were in agreement with EXAFS, both suggesting that iron Fe ions occupied more tetrahedral sites than octahedral sites. Overall, these researchers showed that the aforementioned investigation on their copper ferrite NPs illustrated that these nanostructures had a structure analogous to that of the corresponding bulk material.
The incorporation of the tetravalent metal ions in the spinel structures did not modify the local environment around Cu and Fe ions.
Moroz reviewed the X-ray diffraction structure diagnostics of nanomaterials and stated that a remarkable advantage of EXAFS over REDD radial electron density distribution is its selectivity, whereas REDD is better in providing accurate values of the interatomic distances; in that case, EXAFS provides interatomic distances corrected for the phase shift.
Ideally, REDD should be combined with EXAFS, FTIR and microscopy techniques to acquire knowledge s gilles robust description and matching of images phd thesis the relation between the structure and physicochemical properties of nanomaterials, s gilles robust description and matching of images phd thesis.
combined XRD and EXAFS to determine the cation distribution and other structural parameters, comparing the NP-based sample spectrum with the standard bulk material spectrum of the Cu ferrite. Differences were found among the cation redistribution at the nanoparticle samples with regard to the ideal copper ferrite.
The authors emphasized on the suitability of the technique under discussion for their materials due to its element selectivity and nondependence on the long-range order of materials. From the acquired Debye—Waller factors and the Ce—O bond lengths, it was deduced that the surface or interface of the NPs coated with sodium bis 2-ethylhexyl sulfosuccinate AOT surfactants was quite ordered; however the bond lengths were elongated.
The results implied that Co and Ni ions could occupy both the tetrahedral and octahedral sites with the preference to occupy the octahedral site more than the tetrahedral site, which is different from the bulk sample where all cations occupy only the octahedral site in an inverse spinel ferrite model structure.
synthesized Co SiO 2 core—shell NPs with the sol—gel approach. In situ XRD was used along with EXAFS to monitor the oxidation process of the Co cores after thermal treatment at °C either in air or under an inert atmosphere. Interestingly, it was noticed that Co was oxidized in three steps no matter if air or N 2 gas was employed during the annealing. In particular, EXAFS proved to be very robust for the screening of the initial crystallization behaviour of such amorphous NPs by probing the atomic-level structural change.
Its combination with XRD, HRTEM and VSM helped to investigate in detail the structural changes of Ni—P NPs in both short-range and long-range order during heating at high temperatures. More specifically, XRD illustrated the crystalline phases and phase changes. HRTEM provided information on size, size distribution and shape. EXAFS provided insights regarding the changes of a local atomic structure and the chemical valence, especially for XRD-amorphous samples.
VSM enabled the study of magnetic properties corresponding to different crystallization stages. Metal chalcogenides have also been analysed by EXAFS, as in the case of CdS NPs prepared by Rockenberger et al.
EXAFS can also be used for liquid samples or even in cluster beams in the gaseous phase, permitting the identification of intercluster interactions by comparison with solid state measurements. It revealed that the stabilization of CdS NPs with 1. Unlike XRD, EXAFS is only sensitive to the local geometrical arrangement of neighboring atoms that surround the s gilles robust description and matching of images phd thesis atom.
O'Brien and colleagues investigated the local environment of phosphorus in the capping agent on the surface of CdSe quantum dots.
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