Ligand exchange reactions are commonly employed to modify the surfaces of colloidal semiconductor nanocrystals (NCs), yet multiple reaction pathways induced by the introduction of thiols to NCs have been proposed in the literature to occur independently of each other. Here, we report three separate ligand-based reaction mechanisms between oleate-capped PbS NCs and the exchange thiol ligand, undec-10ene-1-thiol (UDT), and unveil how these three pathways are intertwined. Experimental evidence for these mechanisms is provided by the 1 H NMR spectroscopic handles of oleate-and UDT-based species as well as Pb species quantified by inductively coupled plasma mass spectrometry. We find that Z-type Pb(oleate) 2 ligands are displaced at low quantities of added UDT (0−100 equiv per NC) alongside the coupled binding of L-type thiol ligands to the NC surface. With increasing amounts of added UDT (100−500 equiv), L-type binding of thiol ligands not associated with Z-type displacement is inferred from comparison of the numbers of each bound and free ligand throughout the 1 H NMR spectroscopic titration. Lastly, a substantial quantity of oleic acid is liberated by the reaction of NCs with 100−500 equiv of UDT, suggesting an X-type exchange mechanism, supported by Fourier transform infrared (FTIR) spectroscopic titration. This work provides fundamental insight into changes to the NC surface upon ligand exchange with thiols and proposes site-specific reactivity for each mechanism contextualized within the prior art.
The kinetics of oxidation of the bisbipyridyl and the ethylenebisbiguanide complexes of silver( I) by the peroxydisulphate anion have been studied. The silver(l1)-bipyridyl complex is formed in a reaction which is first order in both reagents, while the silver(ll1) complex is formed by two consecutive reactions, each being first order in both reagents. This evidence suggests that the interaction between silver and peroxydisulphate involves a one-electron process.
The backbone of any field of science is quality data. In personality disorder (PD) science and the broader field of clinical psychology, researchers must consider whether participants were attentive to, understood, and responded honestly and with sufficient effort to self-report questionnaires. We review literature regarding the prevalence of invalid (i.e., careless, low effort, inattentive, or inaccurate) responding, its impact on analysis and interpretation, and available methods of detection. We also present the results of a systematic review of 251 empirical articles across three major journals to characterize the current state of questionable data detection in PD science both in absolute terms and as compared to practices in the larger field of clinical science. In response to the disconcertingly low prevalence rate of self-report validity checks (approximately 22% of PD studies), we conclude by providing practical recommendations for improving data validity in PD science at the points of study design, data analysis, and reporting of results.
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