How can i take XRD from my samples?(They are in a state of aqueous solution)?

Ravi Ananth Popular answer

XRD signal depends on diffraction efficiency of the individual components in your sample. So, when you share further details of the chemical constituents in your "sample", the feed back you'll get would be more precise.

When you use in the "in situ" aqueous form, the composition of the constituent of interest in the diffracting volume will determine the strength of the diffracted signal from that component in the liquid. So, understanding the nature of the sample is critical for further expert advise. Capillary sample holders in XRD for aqueous samples are as old as the science itself :-)

Replacing the amorphous glass with some sort of a "zero background" substrate would yield better SNR (signal to noise ratio), in my opinion.

Consider the "preferred orientation" effects due to any evaporation, spinning, dripping, centrifuging or other methods of removing solvent.

Reasons for "insufficient signal" include diffracting volume, incident beam intensity, monochromation, detector sensitivity, etc.

SAXS (small angle x-ray scattering) may be used to characterize the particulate nature of the aqueous solution.

XRR may be used to characterize thickness and flatness of films and surfaces respectively.

Use of a 2D detector to capture a larger section of the reciprocal space rather than the conventional "spatially blind" equatorial scan diffractogram would greatly enhance the ability to analyze the resulting 2D diffraction data.

Including some literature relevant to the material in question would help the rest of us understand your paradigm better :-)

XRD is a powerful NDE technique that may be used to resolve Nano structural details down to femto-meters (Fermi), if you know what you are doing!

https://www.researchgate.net/post/OAT-Oblique_Angle_Topography_Is_this_the_first_in_the_world_Do_you_know_of_anyone_else_in_literature_that_has_used_this_method_for_magnification

https://www.linkedin.com/pulse/real-time-2d-powder-diffraction-revolutionizing-data-ravi-ananth?trk=mp-reader-card

https://www.flickr.com/photos/85210325@N04/10515372183/in/album-72157645018820696/

Marcin Perzanowski

In such case:

1) Put a drop of your solution on a piece of substrate and leave it to dry. However, you have to pick the substrate carefully to avoid substrate signal overlapping XRD peaks coming from the investigated material. You can use for example Si with different orientations, MgO, or, what is the simplest way, a piece of glass. But in case of the amoprhous glass substrate you have to expect a characteristic "bump" in your pattern.

Or:

2) you have special equipment dedicated to liquids (special stage and capillaries for you XRD machnie).

Mohammad Rehan

Dear Ahmadreza,

Normally you can not do XRD if your sample is in solution unless you are using special synchrotron radiation (ED-XRD). You may want to read our recently published paper on in situ analysis of TiO2 nanoparticles (during their synthesis in solution) using synchrotron radiation.

http://pubs.rsc.org/en/Content/ArticleLanding/2015/CE/c4ce02270j#!divAbstract

For drying. It really depends on your material and how stable its structure is.

For example, if you are working with pharmaceutical materials then simply heating up your sample in an oven may actually degrade or change some crystallographic phases.

Generally for any stable materials (like metal oxide etc.), normally you would first use filtration to remove all excess solvent and then dry your sample in an oven (very roughly 105C for 10-24 hrs, although it really depends on your material, solvents used, amounts and so on).

Once your sample is dried, you can then use that powder sample for XRD analysis.

To add on to above answer by respected colleague (Marcin), if you use a drop of your sample, especially when you mentioned its low concentrated, then you won't have enough material to get any XRD peaks in my experience (and that would also only be possible by using a special capillary not using a normal plate like sample holder).

Wish you all the best.

Rehan

Leandro Piaggi Ravaro

The simplest way to do this is to deposit a film by the technique of spin-coating or dip-coating on a glass slide, let it dry in air for a few minutes, then repeat the process until a large layer of the material is obtained. To measure XRD in the equipment, use "Electron beam at low angle" technique for thin films.

Janez Zavašnik

Hi Ahmadreza,

since you mentioned you have low concentrations, maybe it would be a good start to centrifuge the sample first, especially if you want to avoid excessive heating to evaporate large quantities of solvent.The concentrated solution can be then dripped etc... But of course the drying process strongly depends on the type of solvent. Vacuum-drying can be quick and effective way too...

Ravi Ananth