Nanoparticle Concentrations

Knowledge of the particle number is critical in many of our applications. In trying to rationalize membrane ‘clogging’ by particles for example, it is wise to compare the particle density to pore density at the membrane. When conjugating protein to NPs, it is important to work in a molar excess of protein. In using nanoparticles for visualization of membrane or gel integrity, it is surprising how difficult it can be to tune the dilution to get the right number in a field of view. Adding the same volume of micron-sized particles vs nanoparticles will cause a jump the number density over orders of magnitude and result in blank or overcrowded samples. For these applications and others, we find ourselves converting between standard preparation concentrations of % solids or mg/ml and molarity. The figure below does that conversion once-and-for-all for some of our most common samples.

The numbers file that created this is available here

Screen Shot 2014-04-07 at 10.31.09 AMHere is the same data with concentrations reported in #/ml

 Screen Shot 2014-08-01 at 1.43.49 AM


Professor McGrath holds a BS degree in Mechanical Engineering from Arizona State and a MS degree in Mechanical Engineering from MIT. He earned a PhD in Biological Engineering from Harvard/MIT's Division of Health Sciences and Technology. He then trained as a Distinguished Post-doctoral Fellow in the Department of Biomedical Engineering at the Johns Hopkins University. Professor McGrath has been on the Biomedical Engineering faculty at the University of Rochester since 2001 where he also serves as the director of the graduate program BME and associate director of the URNano microfab and metrology core. McGrath's research was focused on the phenomena of cell migration until 2007 when he founded the interdisciplinary Nanomembrane Research Group to development and apply silicon membrane technologies. Professor McGrath is also a co-founder and past president of SiMPore Inc., a company founded to commercially manufacture silicon membranes and related technologies.

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