I have successfully synthesized np using fs laser but still working to synthesis using ns laser.. It seemed like ns laser need very high power compare to fs laser in order to synthesis np..

Would you please send me that paper for fs? [email protected]

NP produced using femtosecond (fs) laser has many advantages over typical nanosecond (ns) ablation technique.

(1) fs pulse duration is less than electron to ions energy tranafer time. So there is no laser- plasma interaction occurs during fs ablation. This means that total laser enegry is imparted to target and gives more ablation compared to ns ablation.

(2) fs ablation gives more precesion compared to ns ablation.

(3) ultrafast ablation minimizes the formation of droplets which are often found in ns ablation.

(4) fs laser needs less threshold fluence than ns laser and short pulses produce more ablation at lower laser fluence. Some recent works show that we can control NP size using laser pulse width and fluence.

Thanks for all of your contributions :-)

Of course, I agree with all of you that Fs may be more efficient than ns laser for NP production. But, if we put in mid the prices Fs and ns which are 10:1 at least, then we have to think many times before going in Fs solution.

Me too, I am very interest to read about changing and controlling the size of nanoparticles produced by Fs-PLD.

Thanks for your reply...I add some links, which explains size control of nanoparticle using laser and other parameters.

(1) http://jap.aip.org/resource/1/japiau/v108/i5/p053107_s1?isAuthorized=no

(This paper explains pulse duration control on NP syntesis)

(2) attached paper explains how fluence affect on NP size.

(3) http://web.mysites.ntu.edu.sg/ramanujan/Publications/Shared%20Documents/ApplSurfSciRamanujan.pdf

(This paper explains the ambient condition effect on NP size)

Hope this links are useful

how fluence affect on NP size

Walid - I can provide some additional empirical information. The femtosecond laser machining workstations I build were substantially enhanced to manage nanoparticle evacuation, and the laser systems themselves had to be hermetically sealed to prevent nanoparticle debris accumulation on the internal optics. These are measures that greatly exceed what is done with nanosecond pulse and other types of lasers, since femto machining dramatically shifts the center of mass particle size to

Thanks Michael Mielke a lot, do you have publication I can read about your progress!!

Thanks a lot my Dear Anoop K K for your papers.

The biggest advantage of fs laser is that the composition of the target and the composition of the film will be almost same whilst the ns laser can effect the composition if the material you are depositing has elements/compounds/alloys with high vapor pressure. FS laser is electrostatic ablation whilst NS laser is thermal ablation.

It is my understanding that there are regimes where Coulomb explosion can dominate, but under typical ablation conditions (e.g. peak irradiance many times above breakdown threshold) it is the plasma pressure and hydrodynamic expansion that drives material ejection. For sure, the volume of matter that forms the plasma has very high temperature. The key with femto ablation is that this heat does not appreciably diffuse from the local plasma volume.

I am sure the literature has evolved significantly, but there were some great papers on these topics in the early 1990's. For example: http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1005953

In this article, Muller et al. show distinct emission spectra from the ns versus fs plumes.

If cost is not the issue, fs pulses definitely have advantages over ns pulses for synthesis.

In fact ps pulses are found to be efficient for generating higher yield of NPs, more so in liquids.

My Dear Florent Bourquard, Actually I have no experimental experience with NP I would like to start with Polymers if possible. Do you suggest for another martial for NPs ?

Thanks for all of your valuable comments which are very useful for me.

Possible way for detection in this publication:

Article Magnetic Gold Nanoparticles in SERS-Based Sandwich Immunoass...

Thanks Almira Ramanaviciene, for your valuable paper which is very useful for me.

My Dear Friends, I am trying to defense my project "Synthesis and Detection of Nanoparticles using Dual-Pulse Femtosecond Laser-Induced

Breakdown Spectroscopy" and reply the reviewer comments. Could you help in the following comment.

This proposal has two main objectives: (1) the use of a short pulse, femtosecond (fs) laser to generate

nanoparticles by ablating a target and (2) use of the same laser to detect and identify these particles by the

method of laser-induced breakdown spectroscopy, known as LIBS.

***

While both claims are defensible, the proposal is weak for several reasons. From an applied standpoint,

which is the main thrust of the proposal, the improvements likely to be realized using fs lasers are marginal.

Regarding objective (1), while it is true that particles produced with fs lasers have different properties than those produced with ns pulses, it is unlikely that such effects will be competitive with chemical synthetic protocols. Nanoparticles used today in such areas as medicine, sensing, nanoelectronics, and photovoltaic cells have very sophisticated chemical and physical requirements, such as multilayer structures used for drug delivery or aligned nanorod ensembles used in dye-sensitized photovoltaic cells. While there may be specialized cases where laser-generated nanoparticles are preferable, for most applications this methodology is not very competitive with chemical synthesis. Regarding objective (2), ns-LIBS is already capable of

detecting nanoparticles below the threshold for health hazards, as documented by ref. 54 as well as in a paper by Dutouquet et al. (Spectrochimica Acta B, 63, 1183 (2008)). In light of this success, and considering the much lower cost of a ns-based detector, the motivation for using a fs-based detector is weakened.

A further weakness of the proposal is the absence of a plan for quantitative measurement, which is a consequence of using the same laser to generate and detect the particles. For realizing objective (2), it is necessary to use a well-defined mono-dispersed source of nanoparticles to calibrate the detection sensitivity.