Frequently Asked Questions

  1. Do your products require unique sample preparation techniques for TEM imaging?

A stain is usually required to increase the electron density of nanocellulose particles so that they are visible under TEM.  We recommend drying very dilute suspensions of the product on a carbon coated lacey TEM grid followed by staining with 25% uranyl acetate solution for 30 minutes. If the suspension is too concentrated when applying to the grid, the particles will bundle and agglomerate too much to for imagining individual particles.

  1. Do your products require unique sample preparation techniques for SEM imaging?

Gold coating is required to increase the electron density of nanocellulose particles so that they are visible under SEM. We use the following procedure: A piece of conductive glass is applied to an aluminum stage using 5mm carbon tape. One droplet of diluted sample (<<0.5 wt.%) is dropped on the glass and the stage is put in a fume hood overnight to dry or in a vacuum oven operating at low temperature for a few hours. The dried sample is coated with 60 seconds gold sputtering with a thickness on the order of 1-2nm.

  1. How should the products be stored?
  • For the gel products, store under refrigeration.
  • For the powder products, store in a dry place away from ignition sources.
  1. Why is there a layer of water on top of the lignin-coated nanocellulose products?

The lignin-coated nanocellulose material is hydrophobic and will displace water over time. It is recommended that gel materials be stirred thoroughly before use.

  1. What is the shelf life of the products?

For properly stored gel products, we have observed shelf-lives over 1 year. We expect significantly longer shelf-lives for properly stored powder products.

  1. Why are the particle sizes different for the lignin-coated gels and powders?

During the spray-drying process, the gels are passed through the drier’s “atomizer” which sprays tiny droplets of fixed sized in the drying chamber. The droplets dry into bundles about 10-20 micron in size that are composed of individual lignin-coated nanocellulose particles. The lignin-coating prevents the nanocellulose particles from irreversibly bonding together. The bundles can be dispersed into the individual particles by applying sufficient energy (see below).

  1. I can’t disperse the lignin-coated powders. Am I doing something wrong?

The key to redispersing the individual nanocellulose particles in a matrix material is to add sufficient mechanical energy to separate the spray-dried bundles. For low viscosity fluids like water, it can be challenging to redisperse the powders.  Best dispersion results are obtained using high torque melt mixing into viscous polymers, or extrusion. We have also had success dispersing the lignin-coated powders in oils, sometimes with the use of surfactants.  For low viscosity fluids, consider if there is a more viscous resin that you can disperse the powder in, via high torque melt mixing for example, that you could then dissolve into the fluid.

  1. How can I further concentrate the gel products in my lab?

The best way to concentrate the products is by centrifugation. We typically centrifuge at 3,750 RPM for 10 minutes. Vacuum filtration using filters with tight pore size can also be used but this method is very time consuming as the filter paper clogs quickly and drains slow. When filtering, ensure that the filtrate is entirely clear. A cloudy filtrate indicates prodcut loss though the filter paper.

Should you experience difficulties using our products or have further questions, please do not hesitate to contact us at bioplus@americanprocess.com