Revealing the Structural and Chemical Properties of Copper-based Nanoparticles Released from Copper Treated Wood-Dataset

Updated May 11, 2022

May 2022
NIOSH Dataset RD-1036-2022-0

Electron Energy Loss Spectroscopy (EELS) Data

Introduction

Copper-based preservatives consisting of micronized and nanoscale copper particles have been widely used in applications for wood protection. The presence of micronized/nanoscale particles and soluble aqueous copper in copper-treated wood has raised questions regarding the forms of released particles and the potential hazards of exposure during the use of these products. However, the lack of a comprehensive understanding of the chemistry of these Cu species is limiting the future investigation of the toxicity of these materials and their potential health impact on workers. In this work, we used a combination of scanning transmission electron microscope (STEM) and electron energy loss spectroscopy (EELS) to analyze the particles released during the sanding/sawing of copper-treated lumber. We have demonstrated using EELS Cu L2,3 edges with comparative reference spectra to determine the Cu species. Three types of species, including basic copper carbonate (BCC), Cu(0), and Cu(II)-Wood complex, were identified in released wood dust particles. The unbound copper particles also exist as a form of BCC or reduced Cu(0). The morphologies and chemical states of emitted copper particles indicate the potential chemical transformation due to copper-wood interactions.

Data Collection Methods

Aerosol sampling

  • An automatic laboratory tool-testing system was used to generate wood dust aerosols during sawing and sanding three types of wood samples: untreated yellow pine (UYP), micronized copper azole (MCA) treated, and copper azole type C (CA-C) treated lumbers.
  • The dust samples were collected on 37-mm diameter, 0.45-μm pore-size Mixed Cellulose Esters (MCE) membrane filters following NIOSH Method 7402. The sampling flow rate was 12.5 L/min, and a cyclone pre-separator with a D50 of 0.9 μm at this flow rate was used for sampling.

TEM Sample preparation

  • The MCE samples were processed and collected on the 200-mesh nickel TEM grids using the modified NIOSH Method 7402.
  • Reference materials including Cu(II) acetate (powder, 99.99%), Cu(I) oxide (powder, 97%), Cu(II) oxide (powder, <50 nm), Copper(II) carbonate basic(powder, reagent grade) and Cu (powder, 25 nm) were collected on 200-mesh lacey-carbon nickel TEM grids for EELS measurements. These materials were used as analogs for Cu compounds that might be present in the samples.

EELS Measurement

  • The TEM samples were analyzed using a JEOL 2100F TEM operating at a beam voltage of 200 kV. Bright Field (BF) and High Angle Annular Dark Field (HAADF) images were simultaneously acquired in the STEM mode with a 0.5-1 nm probe size.
  • EELS spectra and energy-filtered TEM (EFTEM) images were obtained using a post-column Gatan Image Filter (GIF). The images and spectra were collected and analyzed with the Digital Micrograph software.
  • Core-loss energy-loss spectra were recorded at 200 kV using an energy dispersion of 0.2 eV/channel in the STEM mode with the spot size of 1 nm. In addition, Zero-loss and low-loss spectra were acquired and later used to calculate the relative thickness of the sample and remove plural scattering by Fourier-ratio deconvolution.
  • The Cu-L2,3 edges were fitted with Gaussian functions with the Digital Micrograph software to measure peak locations and widths and calculate the integrated peak intensities.

Citations

C.Wang and C.Qi, Revealing the Structural and Chemical Properties of Copper-based Nanoparticles Released from Copper Treated Wood. RSC Adv. 2022 Apr 11;12(18):11391-11401. doi: 10.1039/d2ra01196d.

Acknowledgements

This work was supported by Nanotechnology Research Center (NTRC) of the National Institute for Occupational Safety and Health (NIOSH) (NTRC- 93908M5).

Chen Wang (xli7@cdc.gov)

Chaolong Qi (hif1@cdc.gov)

Contact

For further information contact:

Chemical and Biological Monitoring Branch (CBMB), Health Effects Lab Division (HELD), National Institute for Occupational Safety and Health (NIOSH), Cincinnati, OH

513-841-4359

Page last reviewed: April 13, 2022