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nanosurface 2006-12-17 06:07

PCCP杂志纳米科技热点文章

[size=3]All HOT articles are available to [b][color=Red]download free of charge[/color][/b].[/size]
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[img]http://www.rsc.org/images/14060647-PCCP-nano-banner_tcm18-57949.gif[/img]

PCCP ([url=http://www.rsc.org/Publishing/Journals/CP/index.asp]Physical Chemistry and Chemica Physics[/url]), An international journal for the fastest publication of high-quality original work in physical chemistry, chemical physics and biophysical chemistry.
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[b]1. Biosensing with conically shaped nanopores and nanotubes[/b]
Youngseon Choi, Lane A. Baker, Heather Hillebrenner and Charles R. Martin, Phys. Chem. Chem. Phys., 2006, 8, 4976
DOI: 10.1039/b607360c2Qh S+Y]-~Sd
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[quote]
[i]1. Could you explain the significance of your article to the non-specialist?[/i]

There is a revolution underway in disease diagnosis, which allows the disease (for example cancer) to be diagnosed very early on, when the prospects for successful treatment and full patient recovery are at their highest. This new approach entails detecting in the patient’s blood a very minute amount of a chemical substance, a “biomarker,” that indicates that the disease is present, but in its very early stages. We would be able to greatly expand this life-saving technology if we had better biosensors that could detect these biomarkers in the patient’s blood. This paper describes a new approach to biosensor design that will allow this next-generation of biomarker sensors to be developed. H8t+{ uK4\
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"We hope to prove that practical real-world sensing devices that can be used at point-of-care (e.g. your doctor's office) can be developed."
- Charles Martin[/box]

[i]2. What has motivated you to conduct this work? [/i]

The need for better biosensors to help in disease diagnosis and treatment. 2wv}6Hc!n$h.C
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[i]3. Where do you see this work developing in the future? [/i]-A$b\*L)h G[
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We hope to prove that practical real-world sensing devices that can be used at point-of-care (e.g., your doctor's office) can be developed.

[i]4. Are there any particular challenges facing future research in this area? [/i]z)O }P+Q|

The use of artificial nanotubes and nanopores as sensors is a field in its infancy. Much basic science remains to be done before practical real-world sensors can be developed. na'}f]6p q0D
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[b]2. Surface grafted polymer brushes as ideal building blocks for smart surfaces[/b]
Feng Zhou and Wilhelm T. S. Huck, Phys. Chem. Chem. Phys., 2006, 8, 3815
DOI: 10.1039/b606415aM P8~\1Z%iJ+Pjc%d
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[quote]
[i]1. Could you explain the significance of your article to the non-specialist? [/i]
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Surface-initiated polymer brushes have received considerable attention over the past 5-10 years as a means to modify surfaces with chemically and mechanically robust thin polymer films. With this review, we aim to highlight some of the recent developments in this field, with an emphasis on some of the unique properties of polymer brushes, which arise from the fact that polymers rather than small molecules are attached to a surface in very high grafting densities.
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[i]2. What has motivated you to conduct this work? [/i]lzL[9|Fad)^4q

Switchable surface properties could be important for many different applications, including sensors and actuators, and our recent work on polyelectrolyte has opened new synthetic pathways to obtaining surfaces with properties that can be controlled over a very wide range in quite straightforward ways, while at the same time allowing different types of triggers (including electrical) to be used for switching.
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[size=3][color=Red][b]"Polymer brushes could play a major role in new developments in soft nanotechnology."
- Wilhelm Huck[/b][/color][/size]
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[i]3. Where do you see this work developing in the future?[/i]

Polymer brushes could play a major role in new developments in soft nanotechnology, providing an interface between biology and inorganic semiconductor-based devices. At the same time, they could play active parts in such devices since they could provide a means to ‘power’ devices at the submicron level, by converting chemical energy into mechanical forces.

[i]4. Are there any particular challenges facing future research in this area? [/i]

More control over the internal architecture is needed, requiring significant contributions from synthetic polymer chemists. However, ultimately, polymer brushes need to be incorporated into actual devices and important questions on how to efficiently control polymer brush transitions and to translate electrical stimuli into directed motion will require collaboration between physicists, chemists and engineers.
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[b]3. Absorption and scattering microscopy of single metal nanoparticles[/b]
M. A. van Dijk, A. L. Tchebotareva, M. Orrit, M. Lippitz, S. Berciaud, D. Lasne, L. Cognet and B. Lounis, Phys. Chem. Chem. Phys., 2006, 8, 3486QN2s^ ?$W
DOI: 10.1039/b606090kN4q)Q7E%F8u(?
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[i]1. Could you explain the significance of your article to the non-specialist? (50-100 words)[/i]

We discuss how to detect and study single metal nanoparticles (diameters 1-100 nm) in an optical microscope. Compared to conventional measurements on ensembles of particles, these new methods radically eliminate ensemble averaging, and directly the time-response of the particles. This feature is particularly appealing for metal nanoparticles, because current synthesis methods always yield particles which differ in size, shape, and distribution of crystal and surface defects, whereas these parameters are unique to every single particle. We believe that these techniques will become more and more important in the fields of nanomaterials and biomolecular sciences.
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[i]2. What has motivated you to conduct this work?[/i]

The common aim of the several groups working on this problem is to better understand the electrical, optical, and mechanical properties of materials at scales much shorter than a micrometer. These properties often differ spectacularly from those of the same materials at larger scales. Another strong motivation is the development of new non-fluorescent labels for single biomolecules such as proteins. Gold nanoparticles are very stable, bio-compatible, and can be detected in live cells down to very small sizes (1.4 nm diameter is the current record for immobilized particles).k3V"A@i _-b0Z

[i]3. Where do you see this work developing in the future?[/i]

The detection limit will be pushed down to even smaller sizes, in order to facilitate covalent coupling with biomolecules. A broad variety of optical techniques (time-resolved, frequency-resolved, nonlinear optics, photoluminescence, enhanced Raman scattering, etc.) will be applied to probe an ever expanding collection of properties of matter at nanoscales.

[i]4. Are there any particular challenges facing future research in this area?[/i]
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The main challenge is to address ever smaller particles, so as to obtain reporter signals for ever smaller scales, and labels as little invasive as possible. Although far-field optical methods have progressed enormously in recent years, near-field optics present specific advantages, and perhaps be crucial to detect very small metal clusters.

[/quote]

[b]4. Solid state NMR studies of photoluminescent cadmium chalcogenide nanoparticles[/b]
Christopher I. Ratcliffe, Kui Yu, John A. Ripmeester, Md. Badruz Zaman, Cristina Badarau and Shanti Singh, Phys. Chem. Chem. Phys., 2006, 8, 3510
DOI: 10.1039/b606507b
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[i]1. Could you explain the significance of your article to the non-specialist? [/i]yJYJ)r6j8V``

Cadmium chalcogenide nanoparticles are well known for their photoluminescent properties. Their electronic structures can be tailored to give different colours by controlling the particles’ size and architecture. Yet the complete characterization of the composition and structure of nanoparticles is notoriously difficult, and it is necessary to use numerous techniques which provide different pieces of information to build up a consistent picture. We have used solid state NMR to provide unique information which, in conjunction with photoluminescence spectra and powder X-ray diffraction, gives insight into atomic and nano-scale detail in CdSe/CdTe nanoparticles synthesised in tri-octyl-phosphine, both for the pure materials but more significantly and for the first time for particles composed of alloys and with layered structures. Furthermore, 13C NMR revealed the surprising feature that the organo-phosphorus coating ligands actively hop around the surface of the particle. 'c?1]6c'W$e{q&s

[color=Red][b]"There are many possibilities for solid state NMR studies of other nanoparticle materials."
- Christopher I. Ratcliffe[/b][/color]
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[i]2. What has motivated you to conduct this work? [/i]
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The primary interest in these materials was to explore their production and stability for potential use as photoluminescent markers in biological applications. However, the main motivation behind the work presented in this paper was to see what new and unique information solid state NMR could provide in the characterization of complex nanoparticles: Could we see size effects in the NMR of nuclei in nanoparticles? Could we distinguish homogeneous alloys from mixtures of nanoparticles of the two components? Could we observe the different components of deliberately layered nanoparticles and say something about the compositions of the layers? w*a/YQwdp"Hk
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[i]3. Where do you this work developing in the feature? [/i]
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Apart from applications to similar layered structures in other Cd materials (for instance we have immediate plans to look at CdS/ZnS nanoparticles) there are many possibilities for solid state NMR studies of other nanoparticle materials, e.g. 115In or 31P in InP nanoparticles or various metal nuclei in metal nanoparticles.

[i]4. Are their any particular challenges facing future research in this area? [/i]
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There are challenges for NMR in the study of nanoparticles containing quadrupolar nuclei where the distribution of environments inherent in such materials will give rise to distributions of quadrupolar broadening, such that perhaps only the most symmetrical environments will be detected. Studies at high field could circumvent or reduce this effect.
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5. [b]Can scanning tunnelling spectroscopy measure the density of states of semiconductor quantum dots?[/b]f2_D5KxTi
Peter Liljeroth, Lucian Jdira, Karin Overgaag, Bruno Grandidier, Sylvia Speller and Daniël Vanmaekelbergh, Phys. Chem. Chem. Phys., 2006, 8, 3845
DOI: 10.1039/b605436f
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[i]1. Could you explain the significance of your article to the non-specialist?[/i]}?hhM/u

Molecules, supra-molecular structures and semiconductor quantum dots are increasingly used as the active components in prototype opto-electrical devices with miniaturized dimensions and novel functions. This means that we need to be able to measure the electronic properties of such single, individual nano-objects.%b4I}qt
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[size=3][color=Red]"Scanning tunnelling spectroscopy allows us to understand the electronic properties of quantum dots in detail on the single dot level"
- Peter Liljeroth[/color][/size]3GJ,MUo'[}4u
In this paper, we explore the conditions under which scanning tunnelling microscopy and spectroscopy can be used to reach this goal and yield quantitative information on the energy levels and Coulomb interactions of semiconductor quantum dots.}:T%A6]"Y0d5|$dz

[i]2. What has motivated you to conduct this work?[/i]
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Nanometre-sized semiconductor particles, so-called quantum dots or artificial atoms, have exciting size-dependent opto-electronic properties. Scanning tunnelling microscopy provides a means to do electronic spectroscopy with sub-nanometre spatial resolution which allows us to understand their electronic properties in detail on a single nanocrystal level. This is crucial for their use in novel applications, such as solar cells, LEDs or lasers.F5st8fB#p5]&L
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[color=Blue]Schematic illustration of the overlap of the different QD orbitals with the tip and the substrate[/color] Q&rz3Tx)s_.PI

[i]3. Where do you see this work developing in the future?[/i]9aT:WH[/syU
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These colloidal quantum dots can be used as building blocks for more complex architectures where new, collective properties are expected to emerge. The properties of the assemblies depend on the individual building blocks as well as the electronic interactions between them. We are currently investigating quantum mechanical coupling in two-dimensional arrays of PbSe nanocrystals, where the high spatial resolution of STM is essential in getting information on how local order is reflected in the electronic properties. CulYg!kQ`
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[i]4. Are there any particular challenges facing future research in this area?[/i]R.j ^v7Z|C1n

It is possible to map the spatial shape of the wave-functions with STM by performing spectroscopy at each point over the quantum dot. The amplitude of the tunnelling resonances is related to the square of the wave-function at the position of the STM tip. This is an extremely challenging experiment and has been demonstrated only for a very limited number of systems (carbon nanotubes by the group of Dekker, InAs quantum dots by the groups of Wiesendanger and Millo). In coupled quantum dots, it would be fascinating to map the orbitals in real space.
[/quote]
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[[i] 本帖最后由 nanosurface 于 2006-12-17 03:15 编辑 [/i]]

zkl1975 2006-12-17 12:10

PCCP Hot Nano paper: Molecules that mimic Schottky diodes

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1. Could you explain the significance of your article to the non-specialist?+]P$W3Y~%yP
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Aviram & Ratner provided the theoretical basis for molecular rectification more than thirty years ago when they proposed a donor-(bridge)-acceptor sequence as the organic counterpart of the p-n junction. Rectification arises because electrons can more readily tunnel from the cathode to acceptor on one side of the device and from the donor to anode on the opposite side. f?z.EqL6L:s
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"There is now widespread interest in molecular scale electronics and this discovery has important implications in the design and synthesis of components with even higher rectification ratios"q~ RP`8W
- Geoff AshwellHowever, current rectification ratios obtained from these ultra-thin films are typically less than 30 at ±1 V: they are too small to have any practical significance but those reported in this paper are in excess of 3000 at ±1 V. The enhancement was achieved by improving the donor/acceptor combination, in this case by using an ionically coupled bilayer arrangement that comprised a cationic donor-(pi-bridge)-acceptor molecule and an anionic phthalocyanine donor: Au|Au-S-C10H20-A+-pi-D|D-|Au.7m3n~:lnn
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Geoff Ashwell !{4w(n"W(YHt
2. What has motivated you to conduct this work?'vf'q$wlu9E

I have been interested in the diode since 1990 when collaborative studies with Roy Sambles at the University of Exeter provided tentative evidence of molecule-induced rectification. The discovery was at first treated with curiosity but, in the last five years, there has been renewed interest and three of the early papers have been cited in total about 600 times. The motivation at first was to verify the molecular origin of the electrical asymmetry and then to improve the rectification ratio from ultra-thin films.
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3. Where do you see this work developing in the future?
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There is now widespread interest in molecular scale electronics and this discovery has important implications in the design and synthesis of components with even higher rectification ratios. There is still a long way to go but these self-assembling molecules appear to provide a link to the ultimate challenge of electronic device miniaturisation.

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4. Are there any particular challenges facing future research in this area? Lm @-G aXm

The main challenge involves the nano-to-macro interface: methods are needed to contact single molecules, which may involve the sculpting of nanometer-scale device structures with electrode gaps of predetermined size to locate electro-active molecules.
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Molecules that mimic Schottky diodes3N-MbqhC(In
Geoffrey J. Ashwell, Barbara Urasinska and Wayne D. Tyrrell, Phys. Chem. Chem. Phys., 2006, 8, 3314
DOI: 10.1039/b604092f

apcvd 2007-03-02 06:53

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jkkxxzz 2007-03-29 14:44

谢谢"hH3c-tS9~*B
受教了～～

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