We demonstrate that the silica shell on nanoparticles formed by a typical Stöber method is inhomogeneous in nature. The outer layer of the shell is chemically more robust than the inner layer, which can be selectively etched by hot water. Methods are developed to "harden" the soft silica shells. These new understandings are exploited to develop versatile and template-free approaches for fabricating sophisticated yolk-shell nanostructures.

The nature of the active aluminum species and their interaction with glucose in water are studied to establish a detailed mechanism for understanding the AlCl3-catalyzed glucose-tofructose isomerization. The combination of activity results with electrospray ionization tandem mass spectrometry (ESI-MS/MS) reveal that [Al(OH)2(aq)] + species contributes a lot to the isomerization. Attenuated total reflection infrared spectroscopy (ATR-IR) results show that glucose undergoes a ring-opening process which is accelerated by the [Al(OH)2(aq)] + species. The binding of acyclic glucose with [Al(OH)2(aq)] + species occurs at the C1-O and C2-O positions of glucose, which initiates the hydride shift of the aldose-to-ketose isomerization. The in-situ 27 Al NMR data elucidate the maintenance of the hexa-coordinated form of Al species throughout the reaction. An obvious kinetic isotope effect (KIE) occurs with the C2 deuterium-labeled glucose, confirming that the intramolecular hydride shift from the C2 to C1 positions of glucose is the ratelimiting step for the isomerization. The apparent activation energy (Ea) of the AlCl3-catalyzed glucose-to-fructose isomerization reaction is estimated to be 110 ± 2 kJ·mol -1 .

We show that embedding of a surface ligand can dramatically affect the metal-metal interfacial energy, making it possible to create nanostructures in defiance of traditional wisdom. Despite matching Au-Ag lattices, Au-Ag hybrid NPs can be continuously tuned from concentric core-shell, eccentric core-shell, acorn, to dimer structures. This method can be extended to tune even Au-Au and Ag-Ag interfaces.

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We performed a systematic experimental kinetics study on AlCl3-catalyzed conversion of glucose to 5-hydroxymethylfurfural (HMF) in NaCl–H2O/tetrahydrofuran (THF) biphasic solvent. The kinetics model covers an extensive reaction network including the parallel and tandem reactions of isomerization, dehydration, decomposition, and polymerization from glucose. The accuracy of the model was verified by a parity plot and statistical significance analysis of the kinetic parameters. A deliberate insight into the intrinsic kinetic properties (reaction rate constant and apparent activation energy) of each subreaction elaborates the regulatory role of THF and NaCl on reaction pathways within the network. That is, THF suppresses the rehydration, degradation, and polymerization of HMF to unwanted byproducts, inhibits fructose-to-HMF dehydration and fructose-to-humins polymerization, but promotes the generation of formic acid (FA) from the direct degradation of both glucose and fructose by facilitating the generation of [Glc/Fru + H–H2O–FA]+ species without formation of levulinic acid (LA); while NaCl promotes the dehydration and polymerization of fructose, decelerates the glucose-to-fructose isomerization, and effectively suppresses glucose-to-humins polymerization. The suppression role of NaCl on glucose conversion may come from the inhibition on mutarotation and ring opening from glucose due to the existence of a hydrogen bond between (C6)­O–H on glucose and Cl– ion. The Brønsted acid (HCl) from the hydrolysis of AlCl3 is responsible for direct glucose/fructose-to-FA degradation, HMF-to-humins polymerization, and HMF-to-FA/LA rehydration. The Lewis acidic [Al­(OH)2(aq)]+ species is active for the reversible glucose-to-fructose isomerization and direct HMF-to-FA degradation, whereas glucose/fructose-to-humins polymerization and fructose-to-HMF dehydration are both Brønsted and Lewis acid-catalyzed. This work highlights a deep understanding of the complicated reaction network in the acid-catalyzed conversion of glucose to HMF in a biphasic solvent.