NIST Special Publication 1200-1 

Reporting Guidelines for the 

Preparation of Aqueous 

Nanoparticle Dispersions 

from Dry Materials

Version 2.1 

J. S. Taurozzi 

V. A. Hackley 

National Institute of Standards and Technology

 Material Measurement Laboratory 

Gaithersburg, MD 20899-8520 

M. R. Wiesner 

Duke University 

Department of Civil and Environmental Engineering 

Durham, NC 27708 

http://dx.doi.org/10.6028/NIST.SP.1200-1 
	 		

 

 

 

NIST Special Publication 1200-1 

NanoEHS Protocols 

	Reporting	Guidelines

for	the	Preparation of

Aqueous Nanoparticle	Dispersions

from	Dry	Materials	

Version 2.1 

J. S. Taurozzi 

V. A. Hackley 

National Institute of Standards and Technology

 Material Measurement Laboratory 

Gaithersburg, MD 20899-8520 

M. R. Wiesner 

Duke University 

Department of Civil and Environmental Engineering 

Durham, NC 27708 

http://dx.doi.org/10.6028/NIST.SP.1200-1 

June 2012 

U.S. Department of Commerce 

John E. Bryson, Secretary 

National Institute of Standards and Technology 

Patrick D. Gallagher, Under Secretary of Commerce for Standards and Technology and Director 
 

 

 

Certain commercial entities, equipment or materials may be identified in this

 document in order to describe an experimental procedure or concept adequately. 

Such identification is not intended to imply recommendation or endorsement by the 

National Institute of Standards and Technology, nor is it intended to imply that the 

entities, materials or equipment are necessarily the best available for the purpose. 

National Institute of Standards and Technology Special Publication 1200-1 

Natl. Inst. Stand. Technol. Spec. Publ. 1200-1, 9 pages (June 2012) 

CODEN: NSPUE 
 

 

 

 

 

 

 

Reporting Guidelines for the Preparation of Nanoparticle Dispersions, Version 2.1

Foreword 

This special publication is one in a series of protocols resulting from a collaborative 

research agreement between the National Institute of Standards and Technology (NIST) 

and Duke University’s Center for the Environmental Implications of Nanotechnology 

(CEINT). The original version of this protocol (Ver. 1.0) was first posted on the CEINT 

web site (http://ceint.duke.edu) and it, along with any other previous version, is 

superseded by this updated special publication version. Updates to this protocol may be 

released in the future. Visit http://nist.gov/mml/np-measurement-protocols.cfm to check 

for revisions of this protocol or new protocols in the series. 

NIST and CEINT are interested in soliciting feedback on this method. We value user 

comments and suggestions to improve or further validate this protocol. Please send your 

name, email address and comments/suggestions to nanoprotocols@nist.gov. We also 

encourage users to report citations to published work in which this protocol has been 

applied. 

 4 
 

 

 

 

 

 

 

 

 

 

Reporting Guidelines for the Preparation of Nanoparticle Dispersions, Version 2.1

1. Introduction 

Toxicity and fate assessment are key elements in the evaluation of the environmental, 

health and safety risks of engineered nanomaterials (ENMs). While significant effort and 

resources have been devoted to the toxicological evaluation of many ENMs, obtaining 

conclusive and reproducible results continues to be a challenge. This can be traced in part 

to the lack of standardized dispersion protocols and the inconsistent application of 

dispersion procedures in relevant biological and environmental matrices (1, 2). In order to 

address these issues, the National Institute of Standards and Technology (NIST) jointly 

with the Center for the Environmental Implications of Nanotechnology (CEINT) have 

developed a series of standardized and validated protocols for the dispersion of ENMs 

from a powdered material source for both human health and environmental testing 

applications. 

2. Principles and scope 

This document provides general guidelines for reporting relevant conditions and critical 

parameters relating to the aqueous dispersion of nanoparticles, by application of 

ultrasonic energy or other mechanical dispersion methods (section A), and an example 

presented as a materials and methods section that can be adapted as needed for different 

nanoparticle sources (Section B). It applies specifically to source engineered 

nanomaterials (ENM) obtained in dry powder form or as concentrated stock suspensions. 

A. General guidelines 

General guidelines consist of a list of parameters that should typically be reported in 

Materials and Methods sections (or alternatively as part of the Supporting 

Documentation) of scientific publications, as well as a list of key characteristics of the 

final nanoparticle dispersion. These guidelines relate exclusively to the dispersion 

process; additional parameters or experimental conditions relating to the synthesis and/or 

testing of the source material may be necessary in order to reproduce the experiment in 

its entirety. 

1. Minimum parameters that should be specified in reporting the preparation of 

nanoparticle dispersions: 

	 Description of powder “as received” 

o	 primary particle size and shape, and method of measurement (e.g. 

transmission electron microscopy) 

o	 specific surface area and method of measurement 

o	 identity of coatings or surface functionality if known 

o	 for commercial sources, product trade name or catalog number together 

with batch/lot number
 

 Description of suspending medium used to disperse particles
 

o	 composition including ionic strength or molar salt concentration 

 5 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reporting Guidelines for the Preparation of Nanoparticle Dispersions, Version 2.1

o	 pH 

o dispersing agent(s) (e.g., surfactant) and concentration(s), if used 

o order in which components were added (where appropriate) 

o	 source and quality of water if prepared or diluted on-site (e.g., ultrapure, 

resistivity value, endotoxin removal, organic carbon removal, final filter 

pore size) 

o for commercial sources, product and batch number(s) as applicable
 

 Description of sample container used during dispersion procedure 

o	 flat, conical or round bottom 

o	 nominal container volume/capacity 

o material type (e.g., glass, Teflon, polyethylene, etc.)
 

 Conditions of sonication (preferred method; if used) 

o	 mass of powder initially added to specified volume of dispersion medium 

o	 volume of sample treated 

o	 type of sonicator used (bath, probe immersion, inverted cup) 

o	 power input to sample (as calibrated: see protocol “Preparation of 

Nanoparticle Dispersions from Powdered Material using Ultrasonic 

Disruption.”[3]) 

o total cumulative treatment time 

o operation mode (continuous or pulsed), if pulsed indicate pulse duration 

o	 tip/probe immersion depth (if used) 

o	 temperature before and after sonication 

o	 whether or not cooling bath was used 

o	 sonicator make, model, maximum power output, probe type/diameter if 

used
 

 Conditions of treatment other than sonication (secondary methods; if used)
 

o	 describe method (e.g., ball milling, high intensity vortexing, 

centrifugation, filtration, etc.) and any relevant details pertaining to device 

or method used including operating viscosity range, mill media 

composition and post-dispersion dilutions 

o	 volume and concentration -or mass- of sample treated as applicable and, 

where appropriate, whether the powder sample was added initially, 

continuously or intermittently 

o total cumulative treatment time 

 Post-treatment storage conditions prior to testing (container material, temperature, 

exposure to light, exposure to oxygen, time) 

 Presence of endotoxins or procedures applied to avoid/remove endotoxins (if 

suspension is to be used for toxicity testing)
 

 Conditions of filtration and/or centrifugation (where appropriate)
 

2. Key characteristics of the final suspension to be reported should include, where 

possible: 

	 Post-treatment mass concentration of particle phase 

 6 
 

 

 

 

 

 

 

 

 

 

 

 

 

Reporting Guidelines for the Preparation of Nanoparticle Dispersions, Version 2.1

	 Particle size distribution and method of measurement in the relevant suspending 

medium, including steps taken to ensure that the particle size distribution is stable 

from the point treatment is suspended to the point of measurement, and 

throughout the duration of relevant tests to be conducted with the material. 

	 pH 

Additional characteristics that may be relevant, especially to subsequent biological 

testing: 

	 For commercial sources, steps should be taken to ensure the as-received material 

reflects the manufacturer’s description 

o	 Comparison of powder characterization to nominal specifications and 

typical values, e.g. moisture content by thermogravimetric analysis 

o	 Evaluation of hydrophilicity/wettability 

o Purity determinations
 

 Post-treatment molar concentration of dissolved species
 

o	 dissolved constituents, e.g. metal or metal oxide species, or total organic 

carbon for carbon-based species 

o	 loss of suspending medium constituents, e.g. nutrients 

o fate of dispersing aids (free and adsorbed concentrations) 

 Description of particle shape, structure, aspect ratio 

 Crystallinity and phase composition (typically determined by x-ray diffraction) 

 Electrophoretic mobility or other measures related to the net nanoparticle surface 

charge and correlation to stated particle composition; and isoelectric or zero point 

of charge value where applicable (note: conditions of measurement, including pH 

and ionic strength, must be identified) 

B. Example procedure for the preparation of a Ag nanoparticle aqueous dispersion, 

presented in the form of a Materials and Methods section 1 

The following example is presented solely for illustrative purposes and does not reflect 

an actual procedure. Accordingly, product and manufacturer names are fictitious. 

The Ag nanoparticles (Product No. 0047, Lot 123) used in this work were obtained 

as a black-colored powder from NanoSilver, Inc. (New York, NY). The primary 

particles as initially received had a number-average diameter of (10 ± 4) nm and a 

roughly spherical shape based on TEM image analysis (Electro II, Electron 

Applications, Tokyo, Japan). A cubic crystalline structure was confirmed by X-ray 

diffraction (XR500, XRDCorp, Baltimore, MD) and a specific surface area of (11 ± 

3) m2/g was determined by nitrogen adsorption using the BET method 

(AccuSorpII, Micro-Surf Corp, Toronto, Canada). The powdered material was 

stored in a desiccator until used. A powder mass of 10 mg was dispersed in 200 mL 

1

 The identification of any commercial product or trade name does not imply endorsement or 

recommendation by the National Institute of Standards and Technology. 

 7 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reporting Guidelines for the Preparation of Nanoparticle Dispersions, Version 2.1

of ultrapure water (resistivity > 18 MΩ·cm, pH 5.8) in a 7 cm diameter, 250 mL, 

flat bottom borosilicate glass beaker, using a Sonomix 400 sonicator (SonoCorp, 

Durham, NC) to create a stock dispersion of Ag NPs. The sonicator was fitted with 

a flat tip, 1⁄2 inch probe and had a maximum power output of 600 W at an operating 

frequency of 20 kHz. Sonication was performed in continuous mode at a delivered 

power of 90 W for 20 min. The beaker was immersed in an ice bath to reduce the 

effect of heating during sonication. The measured temperature increase during 

sonication was 4 C. Power delivered by the probe was verified calorimetrically 

following the method detailed in the NIST Special Publication 1200-2 (3). 

The sonicated dispersion was then manually filtered using a 0.2 μm anodized 

alumina membrane syringe filter (AluPore, Lansing, MI) to remove any residual 

poorly dispersed materials. The Ag particles in the final dispersion had a 

hydrodynamic volume-weighted diameter of (15  5) nm as measured by dynamic 

light scattering at a 90o scattering angle (Nanosizer III, NanoSizeInc, Germany). A 

zeta potential of (-22.5 ± 1.38) mV was calculated at pH 6.5 using the Henry 

equation for conversion of the measured electrophoretic mobility (ZetaNano, 

London, UK). The concentration of Ag NPs in the final dispersion was 212 mg/L 

as determined using inductively coupled plasma-optical emission spectrometry 

(Spectro 5000, Wonder Labs, Phoenix, AZ) after digesting the nanoparticles in 5 % 

HNO3 for 24 h. 

Because these particles were intended for 24 h in vitro studies, the particle size 

distribution of silver nanoparticles suspended at relevant concentrations in DMEM 

(the in vitro cell culture medium) was monitored for 24 h (see “e.g. Results” 

section for further details). All glassware and materials used to prepare suspensions 

were first sterilized with alcohol and samples were prepared in a sterile particle-free 

hood. The ultrapure water used to create the stock suspension was additionally 

treated with an endotoxin removal filter (Biopack, Millipore). The prepared 

dispersions were stored in amber glass vials for no longer than 48 h after 

production and before use. 

3. Abbreviations 

BET Brunauer-Emmett-Teller 

DMEM Dulbecco’s Modified Eagle Medium 

ENM engineered nanomaterial 

PSD particle size distribution 

TEM transmission electron microscopy 

 8 
 

 

 

Reporting Guidelines for the Preparation of Nanoparticle Dispersions, Version 2.1

4. References 

1.	 Roebben, G., Ramirez-Garcia, S., Hackley, V.A., Roesslein, M., Klaessig, F., 

Kestens, V., Lynch, I., Garner, C.M., Rawle, A., Elder, A., Colvin, V., Kreyling, 

W., Krug, H.F., Lewicka, Z., McNeil, S., Nel, A., Patri, A., Wick, P., Wiesner, 

M.R., Xia, T., Oberdörster, G., and Dawson, K., Interlaboratory reproducibility of 

size and surface charge measurements on nanoparticles prior to biological impact 

assessment. J. Nanopart. Res., 2011. 13(7): p. 2675-2687. 

2.	 Taurozzi, J.S., Hackley, V.A., and Wiesner, M.R., Ultrasonic dispersion of 

nanoparticles for environmental, health and safety assessment – Issues and 

recommendations. Nanotoxicology, 2011. 5(4): p. 711-729. 

3.	 Taurozzi, J.S, Hackley, V.A., and Wiesner, M.R., Preparation of Nanoparticle 

Dispersions from Powdered Material Using Ultrasonic Disruption, NIST SP 1200-

2, National Institute of Standards and Technology, Gaithersburg, MD, June 2012. 

 9