This review focuses on in situ functionalization of gallium nitride (GaN) with different adsorbates in the presence of an etchant. The low-temperature aqueous nature of this process provides a safe, environmentally friendly technique for tailoring the semiconductor's properties for various applications. Surface binding to GaN relies on a native oxide layer or direct attachment to the metal center present on the etched surface. The specifics of the binding mechanism are based on the functional groups present on the adsorbate. The effects of the GaN surface polarity and quality on the modification approach are analyzed. The review summarizes the alteration of GaN properties after the in situ treatment. Quantitative data until now have shown changes in morphological, surface chemical, optical, electronic, and aqueous stability properties. The review concludes with a short outlook on future studies associated with this surface modification approach.

This work focused on the modification of milled GaN powder. Successful attachment of a porphyrin derivative to a GaN powder was performed via in situ functionalization in the presence of phosphoric acid. The GaN powder was imaged using scanning electron microscopy and was found to be heterogeneous in nature, adopting no consistent geometry in the aggregates. The aqueous stability of the porphyrin used was observed in deionized water and a solution of phosphoric acid using ultraviolet–visible spectroscopy. Surface chemistry was characterized with x-ray photoelectron spectroscopy and infrared spectroscopy, which identified evidence of successful functionalization through the presence of characteristic peaks. The interface stability of the covalent bond between GaN and porphyrin was evaluated using fluorescence spectroscopy and demonstrated no leaching of dye in water solutions for 20 days.

Four vitamin B12 assays were compared using blood sera from Friesian cows on winter diets or grazing. In herd 1, ten animals were blood-sampled three times at monthly intervals and the vitamin B12 concentration of the sera determined by the Poteriochromonas malhamensis and Lactobacillus delbrueckii assays. At all three sampling dates the results produced by the P. malhamensis assay were significantly greater than those produced by the L. delbrueckii assay. Cows in herd 2 were divided into two groups, each of 30 animals. One group was given a soluble glass bolus releasing cobalt and the other was unsupplemented. Milk yields were recorded throughout the experimental period and herbage samples were taken at intervals for cobalt determinations. Blood samples were taken at intervals from January to September 1983 and the vitamin B12 concentration of the sera determined by four different assay methods: the P. malhamensis and L. delbrueckii microbiological assays and the Becton Dickinson and RIA Products ‘No-boil’ radioassays. The last of these failed to detect vitamin B12 in any sample. There was a significant difference between the results obtained by the three other assays, with the Becton Dickinson radioassay consistently producing the lowest result and the P. malhamensis assay the highest result of the three. There was no significant effect of cobalt supplementation on milk yield.