Science Current Events | Science News |

Light touch keeps a grip on delicate nanoparticles

May 04, 2012
Using a refined technique for trapping and manipulating nanoparticles, researchers at the National Institute of Standards and Technology (NIST) have extended the trapped particles' useful life more than tenfold.* This new approach, which one researcher likens to "attracting moths," promises to give experimenters the trapping time they need to build nanoscale structures and may open the way to working with nanoparticles inside biological cells without damaging the cells with intense laser light.

Scientists routinely trap and move nanoparticles in a solution with "optical tweezers"-a laser focused to a very small point. The tiny dot of laser light creates a strong electric field, or potential well, that attracts particles to the center of the beam. Although the particles are attracted into the field, the molecules of the fluid they are suspended in tend to push them out of the well. This effect only gets worse as particle size decreases because the laser's influence over a particle's movement gets weaker as the particle gets smaller. One can always turn up the power of the laser to generate a stronger electric field, but doing that can fry the nanoparticles too quickly to do anything meaningful with them-if it can hold them at all.

NIST researchers' new approach uses a control and feedback system that nudges the nanoparticle only when needed, lowering the average intensity of the beam and increasing the lifetime of the nanoparticle while reducing its tendency to wander. According to Thomas LeBrun, they do this by turning off the laser when the nanoparticle reaches the center and by constantly tracking the particle and moving the tweezers as the particle moves.

"You can think of it like attracting moths in the dark with a flashlight," says LeBrun. "A moth is naturally attracted to the flashlight beam and will follow it even as the moth flutters around apparently at random. We follow the fluttering particle with our flashlight beam as the particle is pushed around by the neighboring molecules in the fluid. We make the light brighter when it gets too far off course, and we turn the light off when it is where we want it to be. This lets us maximize the time that the nanoparticle is under our control while minimizing the time that the beam is on, increasing the particle's lifetime in the trap."

Using this method at constant average beam power, 100-nanometer gold particles remained trapped 26 times longer than had been seen in previous experiments. Silica particles 350 nanometers in diameter lasted 22 times longer, but with the average beam power reduced by 33 percent. LeBrun says that their approach should be able to be combined with other techniques to trap and hold even smaller nanoparticles for extended periods without damaging them.

"We're more than an order of magnitude ahead of where we were before," says LeBrun. "We now hope to begin building complex nanoscale devices and testing nanoparticles as sensors and drugs in living cells."


* A. Balijepalli, J. Gorman, S. Gupta and T. LeBrun. Significantly Improved Trapping Lifetime of Nanoparticles in an Optical Trap using Feedback Control. Nano Letters. April 10, 2012. Available online

National Institute of Standards and Technology (NIST)

Related Nanoparticles Current Events and Nanoparticles News Articles

NC State researchers create 'nanofiber gusher'
Creating large amounts of polymer nanofibers dispersed in liquid is a challenge that has vexed researchers for years. But engineers and researchers at North Carolina State University and one of its start-up companies have now reported a method that can produce unprecedented amounts of polymer nanofibers, which have potential applications in filtration, batteries and cell scaffolding.

Sharper nanoscopy
The 2014 chemistry Nobel Prize recognized important microscopy research that enabled greatly improved spatial resolution. This innovation, resulting in nanometer resolution, was made possible by making the source (the emitter) of the illumination quite small and by moving it quite close to the object being imaged.

30 years after C60: Fullerene chemistry with silicon
The discovery of the soccer ball-shaped C60 molecule in 1985 was a milestone for the development of nanotechnology.

How green tea could help improve MRIs
Green tea's popularity has grown quickly in recent years. Its fans can drink it, enjoy its flavor in their ice cream and slather it on their skin with lotions infused with it.

Click! That's how modern chemistry bonds nanoparticles to a substrate
Nanoparticles of various types can be quickly and permanently bonded to a solid substrate, if one of the most effective methods of synthesis, click chemistry, is used for this purpose.

Nanospheres cooled with light to explore the limits of quantum physics
A team of scientists at UCL led by Peter Barker and Tania Monteiro (UCL Physics and Astronomy) has developed a new technology which could one day create quantum phenomena in objects far larger than any achieved so far.

Optogenetics without the genetics
Light can be used to activate normal, non-genetically modified neurons through the use of targeted gold nanoparticles, report scientists from the University of Chicago and the University of Illinois at Chicago.

Magnetic brain stimulation
Researchers at MIT have developed a method to stimulate brain tissue using external magnetic fields and injected magnetic nanoparticles -- a technique allowing direct stimulation of neurons, which could be an effective treatment for a variety of neurological diseases, without the need for implants or external connections.

Antibiotic nanoparticles attack respiratory infection and reduce drug side effects
Treating respiratory disease is often difficult because drugs have to cross biological barriers such as respiratory tissue and mucosa, and must therefore be given in large quantities in order for an effective amount to reach the target.

SwRI-led researchers study methane-rich plumes from Saturn's icy moon Enceladus
NASA's Cassini spacecraft has measured a curious abundance of methane spewing into the atmosphere of Saturn's icy moon Enceladus.
More Nanoparticles Current Events and Nanoparticles News Articles

Nanoparticles - Nanocomposites  Nanomaterials: An Introduction for Beginners

Nanoparticles - Nanocomposites Nanomaterials: An Introduction for Beginners
by Dieter Vollath (Author)

Meeting the demand for a readily understandable introduction to nanomaterials and nanotechnology, this textbook specifically addresses the needs of students - and engineers - who need to get the gist of nanoscale phenomena in materials without having to delve too deeply into the physical and chemical details. The book begins with an overview of the consequences of small particle size, such as the growing importance of surface effects, and covers successful, field-tested synthesis techniques of nanomaterials. The largest part of the book is devoted to the particular magnetic, optical, electrical and mechanical properties of materials at the nanoscale, leading on to emerging and already commercialized applications, such as nanofluids in magnetic resonance imaging, high-performance...

Nanoparticles: From Theory to Application

Nanoparticles: From Theory to Application
by G√ľnter Schmid (Editor)

Very small particles are able to show astonishing properties. For example, gold atoms can be combined like strings of pearls, while nanoparticles can form one-, two- and three-dimensional layers. These assemblies can be used, for instance, as semiconductors, but other electronic as well as optical properties are possible.
An introduction to the booming field of "nanoworld" or "nanoscience", from fundamental principles to their use in novel applications.
With its clear structure and comprehensive coverage, backed by numerous examples from recent literature, this is a prime reference for chemists and materials scientists working with and developing nanoparticle systems.
A bestselling title in its second edition. A must-have reference for chemists and materials scientists.

Light Scattering, Size Exclusion Chromatography and Asymmetric Flow Field Flow Fractionation: Powerful Tools for the Characterization of Polymers, Proteins and Nanoparticles

Light Scattering, Size Exclusion Chromatography and Asymmetric Flow Field Flow Fractionation: Powerful Tools for the Characterization of Polymers, Proteins and Nanoparticles
by Stepan Podzimek (Author)

A comprehensive, practical approach to three powerful methods ofpolymer analysis and characterization This book serves as a complete compendium of three importantmethods widely used for the characterization of synthetic andnatural polymers light scattering, size exclusionchromatography (SEC), and asymmetric flow field flow fractionation(A4F). Featuring numerous up-to-date examples of experimentalresults obtained by light scattering, SEC, and A4F measurements,Light Scattering, Size Exclusion Chromatography and Asymmetric FlowField Flow Fractionation takes an all-in-one approach to deliver acomplete and thorough explanation of the principles, theories, andinstrumentation needed to characterize polymers from the viewpointof their molar mass distribution, size, branching, and aggregation.This...

Introduction to Metal-Nanoparticle Plasmonics

Introduction to Metal-Nanoparticle Plasmonics
by Matthew Pelton (Author), Garnett W. Bryant (Author)

Based on a popular article in Laser and Photonics Reviews, this book provides an explanation and overview of the techniques used to model, make, and measure metal nanoparticles, detailing results obtained and what they mean. It covers the properties of coupled metal nanoparticles, the nonlinear optical response of metal nanoparticles, and the phenomena that arise when light-emitting materials are coupled to metal nanoparticles. It also provides an overview of key potential applications and offers explanations of computational and experimental techniques giving readers a solid grounding in the field.

Silver Nanoparticles in the Environment

Silver Nanoparticles in the Environment
by Jingfu Liu (Editor), Guibin Jiang (Editor)

This comprehensive book covers the environmental issues concerning silver nanoparticles (AgNPs). Following an introduction to the history, properties and applications, the environmental concerns of AgNPs is discussed. In the second chapter, the separation, characterization and quantification of AgNPs in environment samples are described in detail. In the remaining parts of the book, the authors focus on the environmental processes and effects of AgNPs, with chapters on the pathway into environment, fate and transport, toxicological effects and mechanisms, as well as the environmental bioeffects and safety-assessment of AgNPs in the environment. This book is designed to describe current understanding of the environmental aspects of AgNPs. It provides a valuable resource to students and...

Silver Nanoparticle Applications: In the Fabrication and Design of Medical and Biosensing Devices (Engineering Materials)

Silver Nanoparticle Applications: In the Fabrication and Design of Medical and Biosensing Devices (Engineering Materials)
by Emilio Alarcon (Editor), May Griffith (Editor), Klas I. Udekwu (Editor)

Exploring the synthesis, characterization, surface manipulation, electron transfer and biological activity of silver nanoparticles, this book examines the fundamentals of the properties and synthesis of these particles. With a renewed interest in silver nanoparticles, this book addresses the need to understand their potential in industrial, medical and other applications. It is divided into six chapters, each written by an expert and providing a comprehensive review of the topic while detailing recent advances made in each specific area. These topics include surface plasmon band, synthesis and characterization, Surface-enhanced Raman spectroscopy (SERS) and plasmon resonance mediated processes, photocatalysis, biomedical applications and biological activity. It also presents the current...

Magnetic Nanoparticles

Magnetic Nanoparticles
by Sergey P. Gubin (Editor)

This interdisciplinary approach to the topic brings together reviews of the physics, chemistry, fabrication and application of magnetic nanoparticles and nanostructures within a single cover. With its discussion of the basics as well as the most recent developments, and featuring many examples of practical applications, the result is both a clear and concise introduction to the topic for beginners and a guide to relevant comprehensive physical phenomena and essential technological applications for experienced researchers.

Nanoparticles: Properties, Classification, Characterization, and Fabrication (Nanotechnology Science and Technology)

Nanoparticles: Properties, Classification, Characterization, and Fabrication (Nanotechnology Science and Technology)
by Aiden E. Kestell (Author), Aiden E. Kestell (Editor), Gabriel T. Delorey (Editor)

In nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. It is further classified according to size: in terms of diameter, fine particles cover a range between 100 and 2500 nanometers, while ultrafine particles, on the other hand, are sized between 1 and 100 nanometers. Similar to ultrafine particles, nanoparticles are sized between 1 and 100 nanometers. Nanoparticles may or may not exhibit size-related properties that differ significantly from those observed in fine particles or bulk materials. This book covers all aspects of nanoparticles.

Microwaves in Nanoparticle Synthesis: Fundamentals and Applications

Microwaves in Nanoparticle Synthesis: Fundamentals and Applications
by Satoshi Horikoshi (Editor), Nick Serpone (Editor)

For the first time, this comprehensive handbook presents the emerging field of microwave technology for the synthesis of nanoparticles. Divided into three parts--fundamentals, methods, and applications--it covers topics including microwave theory, scale-up, microwave plasma synthesis, characterization, and more. This offers both an important volume for academic researchers, and a resource for those in industry exploring the applications of nanoparticles in semiconductors, electronics, catalysis, sensors, and more.

Metal Oxide Nanoparticles in Organic Solvents: Synthesis, Formation, Assembly and Application (Engineering Materials and Processes)

Metal Oxide Nanoparticles in Organic Solvents: Synthesis, Formation, Assembly and Application (Engineering Materials and Processes)
by Markus Niederberger (Author), Nicola Pinna (Author)

Metal Oxide Nanoparticles in Organic Solvents discusses recent advances in the chemistry involved for the controlled synthesis and assembly of metal oxide nanoparticles, the characterizations required by such nanoobjects, and their size and shape depending properties. In the last few years, a valuable alternative to the well-known aqueous sol-gel processes was developed in the form of nonaqueous solution routes. Metal Oxide Nanoparticles in Organic Solvents reviews and compares surfactant- and solvent-controlled routes, as well as providing an overview of techniques for the characterization of metal oxide nanoparticles, crystallization pathways, the physical properties of metal oxide nanoparticles, their applications in diverse fields of technology, and their assembly into larger nano-...

© 2015