Understanding the Nature of Amino Acid Interactions with Pd(111) or Pd-Au Bimetallic Catalysts in the Aqueous Phase

Chiral Recognition on Bare Gold Surfaces by Quartz Crystal Microbalance

Quartz crystal microbalance (QCM) is one of the powerful tools for the studies of molecular recognition and chiral discrimination. Its efficiency mainly relies on the design of the functional sensitive layer on the electrode surface. However, the organic sensitive layer may easily cause dissipation of oscillation or detachment and weaken the signal transfer during the molecular recognition processes. In this work, we reveal for the first time that the bare metal surface without the organic selector layer has the capability for chiral recognition in the QCM system. During the adsorption of various chiral amino acids, relatively higher selectivity of D-enantiomers on gold (Au) surface was shown by the QCM detection. Based on analyses of the surface crystalline structure and density functional theory calculations, we demonstrate that the chiral nature of Au surface plays an important role in the selective binding of specific D-amino acids. These results may open new insights on chiral detection by QCM system. It will also promote the construction of novel chiral sensing systems with both efficient detection and separation capability.

Ratiometric fluorescence nanoprobe for monitoring of intracellular temperature and tyrosine based on a dual emissive carbon dots/gold nanohybrid

A novel dual-emission nitrogen doped carbon dots/gold nanohybrid (NCDs-Au) was designed for specific and sensitive ratiometric detection of intracellular temperature and tyrosine. In this probe, a reductive NCDs was successfully prepared with the use of natural biomass Dendrobium officinale as precursor. The new prepared NCDs acted as both reducers and stabilizers to synthesize a novel NCDs-Au nanohybrid by a facile one-step procedure along with a quantum yield of 14.3%. The prepared nanoprobe showed characteristic fluorescence emissions of NCDs and Au NCs with single-wavelength excitation. Notably, the nanoprobe shows an interesting wavelength-dependent dual response to temperature (448 nm) and tyrosine (660 nm), enabling the two targets to be detected proportionally. As an effective temperature sensor, the nanoprobe exhibited good temperature-dependent fluorescence with a sensational linear response from 5 to 75 °C. In addition, the sensor has a linear response toward tyrosine in the range of 0.5-175 μM with a detection limit of 0.19 μM. Moreover, the fluorescent nanoprobe was successfully applied to ratiometricly monitor the variation of temperature or tyrosine level in cells because of the low cytotoxicity, chemical stability and excellent fluorescence properties. These results suggested that the nanoprobe here has provided the possibility for rapidly biosensing with the acceptable selectivity and sensitivity.