From ligands to binding motifs and beyond; the enhanced versatility of nanocrystal surfaces

Surface chemistry bridges the gap between nanocrystal synthesis and their applications. In this respect, the discovery of complex ligand binding motifs on semiconductor quantum dots and metal oxide nanocrystals opens a gateway to new areas of research. The implications are far-reaching, from catalytic model systems to the performance of solar cells

Unravelling the surface chemistry of metal oxide nanocrystals, the role of acids and bases

We synthesized HfO2 nanocrystals from HfCl4 using a surfactant-free solvothermal process in benzyl alcohol and found that the resulting nanocrystals could be transferred to nonpolar media using a mixture of carboxylic acids and amines. Using solution 1H NMR, FTIR, and elemental analysis, we studied the details of the transfer reaction and the surface chemistry of the resulting sterically stabilized nanocrystals. As-synthesized nanocrystals are charge-stabilized by protons, with chloride acting as the counterion. Treatment with only carboxylic acids does not lead to any binding of ligands to the HfO2 surface. On the other hand, we find that the addition of amines provides the basic environment in which carboxylic acids can dissociate and replace chloride. This results in stable, aggregate-free dispersions of HfO2 nanocrystals, sterically stabilized by carboxylate ligands. Moreover, titrations with deuterated carboxylic acid show that the charge on the carboxylate ligands is balanced by coadsorbed protons. Hence, opposite from the X-type/nonstoichiometric nanocrystals picture prevailing in literature, one should look at HfO2/carboxylate nanocrystals as systems where carboxylic acids are dissociatively adsorbed to bind to the nanocrystals. Similar results were obtained with ZrO2 NCs. Since proton accommodation on the surface is most likely due to the high Brønsted basicity of oxygen, our model could be a more general picture for the surface chemistry of metal oxide nanocrystals with important consequences on the chemistry of ligand exchange reactions

Intercultural education for integrated education system

This paper is a brief description of the current developments in the educational system in the country and the need reform it. In terms of inter-ethnic relations in education, more prominent is the need for its interethnic integration. One of the ways to save and overcome the misunderstandings, and the integration of this system is seen precisely in the intercultural education that acknowledges and respects diversity and supports diversity or diversity in all areas of human life. That kind of education makes the students sensitive to the idea that people have naturally developed a different way of life, customs, traditions, values and worldview. The intercultural education tends to overcome the passive coexistence and to create a developed and sustainable way of living in a multicultural society as ours. This kind of upbringing and education should build individuals with intercultural competences who are capable of living and working in a multicultural environment. Hence, by analysing the advantages, principles, objectives and principles of intercultural education we will point out its necessity and a suitable way for introducing it into the curriculum, with the aim of improving and integrating the inter-ethnicity in the educational system, where it is most necessary and would give productive results in terms of building a healthy, stable and prosperous society. Keywords: multiculturalism, inter-culturalism, integration, educational system reform

Fast, microwave-assisted synthesis of monodisperse HfO₂ nanoparticles

A conventional solvothermal synthesis was compared to a microwave-assisted method for the synthesis of HfO2 nanoparticles. In a microwave, the reaction could be completed in 3 h, compared to 3 days in an autoclave. In the microwave synthesis, the ensemble of particles was found to have a better size dispersion and a smaller average size (4 nm). The reaction mechanism was investigated and proof for an ether elimination process was provided. Post-synthetic modification with dopamine or dodecanoic acid permitted the suspension of the synthesized particles in both polar and apolar solvents, which is an advantage for further processing

Amino acid-based stabilization of oxide nanocrystals in polar media : from insight in ligand exchange to solution H-1 NMR probing of short-chained adsorbates

Ligand exchange is a crucial step between nanocrystal synthesis and nanocrystal application. Although colloidal stability and ligand exchange in nonpolar media are readily established, the exchange of native, hydrophobic ligands with polar ligands is less systematic. In this paper, we present a versatile ligand exchange strategy for the phase transfer of carboxylic acid capped HfO2 and ZrO2 nanocrystals to various polar solvents, based on small amino acids as the incoming ligand. To gain insight in the fundamental mechanism of the exchange, we study this system with a combination of FTIR, zeta potential measurements, and solution H-1 NMR techniques. The detection of surface-associated, small ligands with solution NMR proves challenging in this respect. Tightly bound amino acids are undetectable, but their existence can be proven through displacement with other ligands in titration experiments. Alternatively, we find that methyl moieties belonging to bound species can circumvent these limitations because of their more favorable relaxation properties as a result of internal mobility. As such, our results are not limited to amino acids but to any short-chained ligand and will therefore facilitate the rigorous investigation and understanding of various ligand exchange processes

Parental Choices and the Prospect of Regret: An Alternative Account

Is the question ‘will you regret it if you do (not do) this?’ helpful when people face difficult life decisions, such as terminating a pregnancy if a disability is detected or deciding to become a parent? Despite the commonness of the question in daily life, several philosophers have argued lately against its usefulness. We reconstruct four arguments from recent literature on regret, transformative experience and the use of imagination in deliberation. After analysis of these arguments we conclude that the prospect of regret remains a useful deliberative heuristic, provided four conditions are fulfilled. If the prospect of (the absence of) regret is arrived at via reflection on one’s values, in a non-coercive context, when well-informed about factual circumstances, and in a process of self-commitment, the question of what one will regret is a helpful device to get in touch with one’s deepest concerns that give reasons to act in a particular way.status: publishe