Protocol. Indranil Chowdhury Chemical and Environmental Engineering, University of California, Riverside

Transcription

1 Protocol Project Title PI Theme Version Number: 2.0 Production Start Date: Version 2.0 Date: 01/10/12 Authors: Department: Contact Phone # s: Reviewed/Revised by: Zhaoxia (Ivy) Ji Aqueous Dispersion of Metal Oxide Nanoparticles Dr. Sharon Walker 1, 4, Quantitative determination of fate and transport of nanoparticles in porous media Dr. Sharon Walker Indranil Chowdhury ichowdhury@engr.ucr.edu, swalker@engr.ucr.edu Chemical and Environmental Engineering, University of California, Riverside This protocol has been published in whole or in part in the following journal article: (1) Chowdhury, I.; Hong, Y.; Walker, S. L., Container to characterization: Impacts of metal oxide handling, preparation, and solution chemistry on particle stability. Colloids and Surfaces A: Physicochemical and Engineering Aspects 2010, 368, (1-3), Summary This protocol describes handling and preparation methods for characterizing nanoparticles, specifically metal oxide nanoparticles. Characterization parameters include electrophoretic characterization including EPM and Zeta Potential, and hydrodynamic diameter by Dynamic Light Scattering (DLS). Background and Project Goals This effort has been to develop experimental handling approaches, for particles from dry state in the container to the final suspended stage used in characterization, transport, and toxicology studies. Specifically, the effects of sonication, as well as nanoparticle concentration upon the size, electrophoretic mobility, and stability of model metal oxides (TiO 2, CeO 2 and ZnO) have been investigated and appropriate procedures developed to ensure reproducible results. In this protocol, Titanium dioxide (Evonik Degussa Coorporation, NJ), cerium dioxide (Meliorum Technologies, NY) and zinc oxide (Meliorum Technologies, NY) nanoparticles were used as model metal oxide nanomaterials with more than 99.5% pure. The primary particle size for TiO 2, CeO 2 and ZnO were determined to be 21 nm, 10 nm and 10 nm, respectively. 1/5

2 Materials & Reagents Materials/Reagents/Equipment Disposables 50 ml centrifuge tubes Glass beakers 100 nm filters (Anotop 25) Reagents Deionized water (>18.2 MΏ at 25 o C) Potassium Chloride Potassium Hydroxide Hydrochloric Acid Ethanol Equipment ZetaPALS analyzer Dynamic Light Scattering (DLS) Brookhaven model BI-9000AT digital correlator Sonicator with water bath (Transsonic 460/H) Vortexer Vendor Whatman, Middlesex, UK Brookhaven Instruments Corp., Holtsville, NY Brookhaven Instruments Corp., Holtsville, NY Barnstead/Lab-line, Melrose Park, IL Stock Number(s) D, 02540K P217-3 SP SA481 Laboratory Safety Precautions Nanoparticles (dry powders) handling has to be done in chemical fume hood and with N95 filter mask. Scientists performing this procedure must wear a lab coat and gloves. In situations where there might be a chance of an accidental splash to the eyes, safety glasses must be worn. Please refer to the Nanotoolkit produced by the California Nanosafety Consortium of Higher Education for recommendations regarding safe handling and disposal of nanomaterials. Prior to suspension of the 2/5

3 nanoparticles, use engineering controls, work practices, and PPE as specified for Category 2 (Moderate Exposure Potential); after suspension, use use engineering controls, work practices, and PPE as specified for Category 1 (Low Exposure Potential) as specified in the Nanotoolkit. As described in the Nanotoolkit, NIOSH has determined that workers may be at risk of developing adverse respiratory health effects if exposed to certain nanomaterials for a working lifetime at the upper limit of quantitation (LOQ) using NIOSH Method 5040, which is currently the recommended analytical method for measuring airborne CNTs. The LOQ for CNTs using NIOSH Method 5040 is 7 μg/m3. Animal data-based risk estimates from NIOSH indicate that workers may have >10% excess risk of developing early stage pulmonary fibrosis if exposed over a full working lifetime at the upper LOQ for NIOSH Method Until improved sampling and analytical methods can be developed, and until data become available to determine if an alternative exposure metric to mass may be more biologically relevant, NIOSH is recommending a REL of 7 μg/m3 elemental carbon (EC) as an 8-hr TWA respirable mass airborne concentration. a Likewise, NIOSH recommends airborne exposure limits of 2.4 mg/m3 for fine TiO2 and 0.3 mg/m3 for ultrafine (including engineered nanoscale) TiO2, as time-weighted average (TWA) concentrations for up to 10 hr/day during a 40-hour work week. These recommendations represent levels that over a working lifetime are estimated to reduce risks of lung cancer to below 1 in 1,000. The recommendations are based on using chronic inhalation studies in rats to predict lung tumor risks in humans. b Citations: a NIOSH. (2010). Occupational Exposure to Carbon Nanotubes and Nanofiber. Current Intelligence Bulletin. b NIOSH. (2011). Occupational Exposure to Titanium Dioxide. Current Intelligence Bulletin. 3/5

4 Pilot Workflow Figure 1. Schematic of aqueous dispersion of metal oxide nanoparticles protocol Pilot Procedure Procedure for Sample Preparation Prepare nanoparticle stock suspension by adding 1 g/l of dry nanoparticles to the background solution (e.g., nanopure water at >18.2 MΏ at 25 o C) and stirring with a magnetic stir bar for 1 minute, followed by sonication. We recommend sonicating in a water bath at 120 W (Transsonic 460/H, Barnstead/Labline, Melrose Park, IL). An optimum sonication time of 30 minutes was determined using the Transsonic 460/H sonicator by varying the duration of sonication until a minimum aggregate size as measured by dynamic light scattering. If you are using a different sonicator, you should similarly optimize the sonication time. This stock is then diluted in the appropriate electrolyte solution for future experiments and resonicated. An optimal sonication time of 30 seconds for our system was determined to produce the minimum aggregate size, as measured by DLS. If you are using a different sonicator, you should similarly optimize the sonication time for this second step. 4/5

5 SOP Approval DEPARTMENT APPROVED BY DATE Principal Investigator Sharon Walker /5