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 served as the director of the graduate program in BME for more than a decade and currently serves as Associate Director of the URNano microfab and metrology core. Professor McGrath also has faculty affiliations with many other programs at UR including the Material Research Program, the Environmental Health and Sciences Center, the Biochemistry and Biophysics program, and the Musculoskeletal Research Center. McGrath's graduate, post-doctoral, and early faculty research was focused on quantitative experiments and mathematical modeling of cell migration covering molecular, cellular, and multi-cellular phenomena. This was true until 2007 when he, along with Professor Philippe Fauchet (now Dean at Vanderbilt) and PhD students Tom Gaborski (RIT) and Chris Streimer (Adarza), discovered a means to self-assembled nanopores in 15 nm thick free-standing silicon and demonstrated the remarkable transport properties of the new material in a Nature paper. This seminal discovery led to the creation of the multidisciplinary Nanomembrane Research Group (NRG) and the founding of SiMPore Inc. in the same year. The NRG and SiMPore have been dedicated to the advancement of ultrathin membrane technologies and exploring all of their potential applications ever since. This blog also dates back to 2007 and has had contributions from more than 100 students, faculty, scientists, engineers, and entrepreneurs. It contains over 2,500 pages and posts logging progress large and small over all these years. Yet somehow it feels like we are just getting started.

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