In this study, perfluorinated phosphonic acid modifications were utilized to modify zinc oxide (ZnO) nanoparticles because they create a more stable surface due to the electronegativity of the perfluoro head group. Specifically, 12-pentafluorophenoxydodecylphosphonic acid, 2,3,4,5,6-pentafluorobenzylphosphonic acid, and (1H,1H,2H,2H-perfluorododecyl)phosphonic acid have been used to form thin films on the nanoparticle surfaces. The modified nanoparticles were then characterized using infrared spectroscopy, X-ray photoelectron spectroscopy, and solid-state nuclear magnetic resonance spectroscopy. Dynamic light scattering and scanning electron microscopy-energy dispersive X-ray spectroscopy were utilized to determine the particle size of the nanoparticles before and after modification, and to analyze the film coverage on the ZnO surfaces, respectively. Zeta potential measurements were obtained to determine the stability of the ZnO nanoparticles. It was shown that the surface charge increased as the alkyl chain length increases. This study shows that modifying the ZnO nanoparticles with perfluorinated groups increases the stability of the phosphonic acids adsorbed on the surfaces. Thermogravimetric analysis was used to distinguish between chemically and physically bound films on the modified nanoparticles. The higher weight loss for 12-pentafluorophenoxydodecylphosphonic acid and (1H,1H,2H,2H-perfluorododecyl)phosphonic acid modifications corresponds to a higher surface concentration of the modifications, and, ideally, higher surface coverage. While previous studies have shown how phosphonic acids interact with the surfaces of ZnO, the aim of this study was to understand how the perfluorinated groups can tune the surface properties of the nanoparticles.

This study demonstrates the validation of a semi-quantitative method for the rapid screening of whole blood and urine specimens using clonazepam as the target molecule for the Neogen (R) Benzodiazepine kit. Decision points were validated at 10.0 ng/mL for whole blood and 25.0 ng/mL for urine. The validation design was based on the Scientific Working Group for Forensic Toxicology (SWGTOX) Standard Practices for Method Validation and included the evaluation of sensitivity, precision, specificity, carryover, hook effect, drift, ruggedness/robustness and a case sample evaluation. The experimental limit of detection for clonazepam was determined to be at least 5.0 ng/mL in whole blood and at least 10.0 ng/mL in urine. Excellent precision was demonstrated when the assay was evaluated using the mean of three replicates from five separate runs (n = 15) at the decision point and at concentration levels +/- 50% and +100% of the decision point. Although the method was optimized and exceptional precision was demonstrated at each level, the current SWGTOX validation requirements for a valid decision point were not fulfilled. However, both the blood and urine matrix did meet the proposed revision of the SWGTOX requirements for determining a valid decision point promulgated by the American Academy of Forensic Sciences Standards Board and the assay was reliably able to detect benzodiazepines without interference from matrix components or other compounds routinely detected in authentic case samples. Case sample results were comparable with those obtained when the samples were initially screened using oxazepam as the target molecule. The Neogen (R) Benzodiazepine kit using clonazepam as the target molecule exhibited cross-reactivity for 29 different benzodiazepines and demonstrated excellent precision and sensitivity in both whole blood and urine, making it an efficient and reliable method to screen for benzodiazepines, even though the validation did not fulfill current SWGTOX requirements for a valid decision point.