Study of the affinity of thermographic additives for silver by time-of-flight static secondary ion mass spectrometry and surface-enhanced Raman spectroscopy on silver nanoparticles.

Detection of the interactions between low molecular weight organic compounds and metals in the form of sols on a nanoscale is analytically challenging. This study aims to provide experimental evidence using a combination of UV-Vis absorption spectrometry, surface-enhanced Raman spectrometry (SERS), and static secondary ion mass spectrometry (S-SIMS). The field of application is thermography where silver images are formed via heat-catalyzed reactions. Several organic compounds called tone modifiers and stabilizers are used in thermographic materials for the optimization of the image quality. With exploitation of the strengths of each of the above-mentioned methods, an affinity ranking of several tone modifiers and a stabilizer was established on the basis of competitive adsorption experiments using different model systems. Specifically, silver sols, SERS probes, and sputter-coated silver substrates were exposed to systems with one or two additives. The UV-Vis results provided insight on the aggregation of silver nanoparticles in a hydrosol, which was necessary for the interpretation of the SERS data. Both SERS and S-SIMS measurements led to a similar ranking of the relative affinity of the additives in two components, which was largely consistent with empirical knowledge derived from macroscopic behavior.

Feasibility of static secondary ion mass spectrometry to study physicochemical interactions between organic components and silver in thermographic systems.

Chemical engineering of high-technology products requires elucidation of intermolecular interactions in complex materials. As part of an extensive study on thermographic systems, static secondary ion mass spectrometry (S-SIMS) was used to probe the physicochemical behaviour of active compounds, such as different tone modifiers and stabilisers, on silver. In particular, the feasibility of detecting adsorption and/or binding of individual additives and mixtures to silver was examined. Substrates prepared by sputter coating silver on silicon wafers were exposed to solutions of the studied compounds in 2-butanone. The signal intensities measured with S-SIMS for the ad-layers showed reproducibility to within 10%. Radical ions containing silver such as [M-H+Ag]+ * were used as evidence for the formation of bonds in the solid. Also the [M-H+2Ag]+ ions could be assigned to chemisorbed species while [M+Ag]+ ions could be formed by adduct ionisation of molecules with co-ejected Ag+ ions. The signal intensities of [M-H+Ag]+ * and [M-H+2Ag]+ ions were used to monitor the adsorption quantitatively as a function of time.

Determination of ultra-trace amounts of Fe in AgNO3 solutions by means of isotope dilution analysis applying an inductively coupled plasma mass spectrometer equipped with a dynamic reaction cell.

The development of an ICP-MS method for the determination of ultra-trace amounts of Fe in AgNO(3) solutions using isotope dilution for calibration is described. AgNO(3) solutions are used as raw materials in the production of traditional photographic materials, and it is known that contamination with metal traces can influence the quality of the films thus produced. After adding an appropriate amount of an (54)Fe-enriched spike and permitting isotopic equilibration to take place, Ag was selectively removed from the solutions by precipitation as AgBr. Although to some extent, co-precipitation of Fe is possible under the given circumstances, an incomplete recovery of the analyte element did not affect the accuracy of the results, owing to the use of isotope dilution for calibration. NH(3) was used as a reaction gas in a quadrupole-based ICP-MS instrument, equipped with a dynamic reaction cell (DRC), providing interference-free measurement of the (54)Fe/(56)Fe ratio. The limit of detection (LOD) obtained using this procedure was approximately 0.01 micro g g(-1). This is an excellent value in comparison with the detection limit obtained with the more traditional approach: sample dilution and external calibration with a Fe standard solution (LOD ~1 micro g g(-1)). To validate the method, recovery experiments were carried out. In all instances, a quantitative recovery was established. Finally, the method was applied to the analysis of AgNO(3) solutions. A large variation in Fe concentration was observed. Depending on the Fe content in the samples, relative standard deviations typically ranged between 1 and 14%.

Chemical microcharacterization of ultrathin iodide conversion layers and adsorbed thiocyanate surface layers on silver halide microcrystals with time-of-flight SIMS.

The technique of imaging time-of-flight secondary ion mass spectrometry (TOF-SIMS) and dual beam depth profiling has been used to study the composition of the surface of tabular silver halide microcrystals. Analysis of individual microcrystals with a size well below 1 microm from a given emulsion is possible. The method is successfully applied for the characterization of silver halide microcrystals with subpercent global iodide concentrations confined in surface layers with a thickness below 5 nm. The developed TOF-SIMS analytical procedure is explicitly demonstrated for the molecular imaging of adsorbed thiocyanate layers (SCN) at crystal surfaces of individual crystals and for the differentiation of iodide conversion layers synthesized with KI and with AgI micrates (nanocrystals with a size between 10 and 50 nm). It can be concluded that TOF-SIMS as a microanalytical, surface-sensitive technique has some unique properties over other analytical techniques for the study of complex structured surface layers of silver halide microcrystals. This offers valuable information to support the synthesis of future photographic emulsions.