Thesis: Raman spectroscopy of nanomaterials: applications in Archaeology

Title: Micro-Raman spectroscopy of nanomaterials: applications in Archaeology
Author: Linda Charlotta Prinsloo
University: University of Pretoria
Year: 2008
Type of Document: PhD thesis
Link: http://up.ac.za/... (pdf)

Abstract:

“Nanomaterials” is a generic term used to describe nano-sized crystals and bulk homogenous materials with a structural disorder at the nanoscale. Ancient (and modern) ceramics and glasses derive some of their properties (eg. pliability and low sintering temperature) from the fact that their raw material namely natural clay is nanosized. Furthermore the pigments used to colour ceramics and glasses need to have particle sizes 500 nm for the object to appear homogenously coloured to the human eye. Raman spectroscopy intrinsically probes chemical bonds and is therefore one of the few techniques that has been proven useful to provide information at the nanoscale. It is an excellent tool to study ceramics and glasses as a Raman spectrum can be used to identify phases, analyse amorphous domains in the silicate network and identify pigments on a nano-scale. The characteristics of a glass, ceramic or ceramic glaze derived through its Raman spectrum can then be linked to the technology used to produce an artefact and in this way provide information about its relative age and provenance. Likewise, the identification of pigments and binders in San rock art might provide information about production techniques and assist in the developement of conservation procedures. In this thesis micro-Raman spectroscopy (with X-ray fluorescence, X-ray powder diffraction, electronmicroscopy and photoluminescence as supportive techniques) was utilised to study archaeological artefacts from the Mapungubwe Collection and San rock art. It was possible to re-date celadon shards excavated on Mapungubwe hill in 1934 to the Yuan or even later Ming dynasty in stead of its original classification as Song. A profile of the glass technology used to produce the Mapungubwe oblates, small trade beads from the “royal burials” on Mapungubwe hill was determined and quite a few unique characteristics of the beads may eventually help to establish their provenance. The possible influence of the presence of rock hyraces at rock art sites on the deterioration of rock art were investigated and during the study very rare polymorphs of CaCO3 (vaterite and monohydrocalcite) were discovered in rock hyrax urine. This study was extended to analyse a San rock art fragment and another first was the identification of animal fat on the fragment, but the exact origin of the fat has to be verified by similar experiments.

Table of contents (short version):

1. Introduction
2. Theoretical Background
3. Re-dating of Chinese celadon shards excavated on Mapungubwe Hill, a 13th century Iron Age site in South Africa, using Raman spectroscopy, XRF and XRD
4. A Raman spectroscopy study of the Mapungubwe oblates; glass trade beads excavated at an Iron Age archaeological site in South Africa
5. Rock hyraces: a cause of San rock art deterioration?
6. The first Raman spectroscopy study of San rock art in the uKhahlamba Drakensberg Park, South Africa
7. Conclusions

Thesis: Oddy Test Using Silver Nanoparticle Sensor (2007)

Title: Nanoscience and Nanotechnology Applied to Art Conservation: Improved Oddy Test Using Silver Nanoparticle Sensor
Author: Laura Moussa
University: Carnegie Mellon University
Pages: 63
Year: 2007
Type of document: thesis
Link: http://www.cmu.edu/... (pdf, 4.3 Mb)

Abstract:

Damage to metal artifacts from the materials used for display and storage cases is of great concern to art museums. The current technology used, the “three in one” Oddy Test, tests for the suitability of these construction materials by placing silver, copper, and lead metal coupons in one container along with the material at 60°C and 100% relative humidity. After a 28-day period the metal coupons are assessed for any visual changes. There are many shortcomings to this simple test. It is time consuming, irreproducible, slow, hard to evaluate and most importantly gives no quantitation. A new way to test for the suitability of these materials using a silver nanoparticle sensor is described here. Two types of silver nanoparticle shapes, spherical and triangular, were self-assembled using polyethylenimine (PEI) onto a glass coverslip to produce two different sensors. The spherical nanoparticle sensor gave a yellow color and when evaluated for its sensitivity to hydrogen sulfide gas changed colors from yellow to colorless. The triangular nanoparticle sensor gave a blue color and when evaluated for its sensitivity to hydrogen sulfide gas changed colors from blue to colorless. Color changes were followed through UV-Vis spectrophotometry, which showed a decrease in absorption of the initial characteristic peak after exposure to hydrogen sulfide. Kinetic studies were performed on the spherical and triangular nanoparticles, and the reaction rates were determined to be first-order with k = 0.0002 for the triangular nanoparticles and k = 0.0001 for the spherical nanoparticles. When compared to the Oddy Test, both the spherical and triangular silver nanoparticle sensors reacted fully by showing the characteristic color change before the 28-day period of the test. The nanoparticle sensor will allow for high sensitivity, easy evaluation, and quantitative analysis for corrosive gases that would react with silver.

Table of contents (short version):
Chapter 1-Introduction
Chapter 2- Sensor Fabrication
Chapter 3-Sensitivity of Nanoparticles to Hydrogen Sulfide
Chapter 4-Performance evaluation of Ag nanoparticle sensors
Chapter 5- Conclusion and future work
References