Table III.

Strengths and limitations of primary methods discussed in this review.

Technique	Strengths	Limitations or issues
XPS	Generally available and easy to obtain useful qualitative information about the near surface region of films or particles Identifies unexpected elements and oxidation state Useful to estimating average coating thickness less than 10 nm Significant range of other quantitative information possibleusing detailed analysis and modeling	Needs appropriate sample preparation and handling to minimize information loss. Requires vacuum Laboratory configurations cannot analyze individual particles, requires collection of particles New developments could speed quantitative analysis of nanomaterials
AES	Identifies unexpected elements present Useful for estimating coating thickness if less than 10 nm With limitations can characterize individual nanoparticles	Requires vacuum Needs appropriate sample preparation and handling to minimize information loss Beam damage a concern, particularly with regard to insulators and organic particles and coatings
SIMS	Can provide molecular information about film and particles surfaces Determine presence of trace elements	Most instruments cannot characterize individual particles, therefore requires a collection of particles Needs appropriate sample preparation and handling to minimize information loss Sputter rates accelerated for nanoparticles Nanoparticles can melt or transform, sputtering can destroy the size, shape, and composition of the particles Requires vacuum
LEIS	Sometimes describes as the most surface sensitive analysis method Easily determines the presence of elements at the outer atomic layer of a sample, therefore great at looking at coating uniformity and presence of some defects on nanoparticle and flat surface coatings	Contamination easily masks signal, needs careful sample preparation and handling to minimize information loss Requires vacuum and a collection of particles for analysis—high sensitivity
MEIS	With sample structure modeling provides high resolution depth distribution in films and particles	Cannot analyze individual particles and most information if single layer of particles on a substrate that does not interfere with desired analysis Requires vacuum
AFM	Easily identifies presence of particles and particle shape on a flat surface Measurements can be made in vacuum, gas or liquid environments	Tip shape can become convoluted with measurements Cannot provide direct chemical information
STM	Easily visualize presence of particles Can be conducted in vacuum, gaseous and in some cases liquid environments	No direct structural or chemical information Requires some degree of electrical conduction
SFG-VS	Selectively probe chemical identity, molecular structure and interactions from vibrational spectra of particle surfaces or interfaces in vacuum, liquid or gaseous environment with submonolayer sensitivity No need for total internal reflections	Requires modeling and spectral data interpretation
NMR	Molecular information available from a variety of environments	Not inherently surface sensitive “Tricks” may need to be employed to obtain sensitivity and extract desired information