Self-assembled monolayers (SAMs) were formed by the spontaneous adsorption of octythiocyanate (OTC) on Au(111) using both solution and ambient-pressure vapor deposition methods at room temperature and 50 degrees C. The surface structures and adsorption characteristics of the OTC SAMs on Au(111) were characterized by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). The STM observation showed that OTC SAMs formed in solution at room temperature have unique surface structures including the formation of ordered and disordered domains, vacancy islands, and structural defects. Moreover, we revealed for the first time that the adsorption of OTC on Au(111) in solution at 50 degrees C led to the formation of SAMs containing small ordered domains, whereas the SAMs formed by vapor deposition at 50 degrees C had long-range ordered domains, which can be described as (radical3 x 2 radical19)R5 degrees structures. XPS measurements of the peaks in the S 2p and N 1s regions for the OTC SAMs showed that vapor deposition is the more effective method as compared to solution deposition for obtaining high-quality SAMs by adsorption of OTC on gold. The results obtained will be very useful in understanding the SAM formation of organic thiocyanates on gold surfaces.

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Metal complexation-based gelation imparts load-bearing hydrogels with striking properties like reversibility, self-healing, and mechanical tunability. Using a bio-inspired metal−catechol complex, these properties have been introduced to a variety of polymer hydrogels, except hyaluronic acid, which is widely used in biological applications. In this research, we developed two different hyaluronic acid (HA) hydrogels by regulating the gelation kinetics of Fe 3+ and a catechol cross-linker, including Fe 3+ -induced covalent bonding and coordination bonding. Dual roles of Fe 3+ in catechol-modified HA (HA-CA), Fe 3+ −catechol coordination, and catechol oxidation followed by a coupling reaction were selectively applied for different gelations. Phase-changeable HA-CA gel was attributed to dominant Fe 3+ −catechol coordination with immediate pH control. Alternatively, allowing a curing time to form catechol coupling bonds resulted in color-changeable HA-CA gels with pH control. The gel structure is then preserved by dual cross-linking through covalent catechol-coupling-based coordinate bonds and electrostatic interactions between Fe 3+ and HA-CA. The hydrogels showed enhanced cohesiveness and shock-absorbing properties with increasing pH due to coordinate bonds inspired by marine mussel cuticles. The present gelation strategy is expected to expand the utility of HA hydrogels in biological applications, offering easy control over the phase, gel network, and viscoelastic properties.

Calibration models are generated and evaluated for the measurement of five different components in synthetic mixtures prepared in aqueous solutions. Mixtures of glucose, glutamine, ammonia, lactate, and glutamate were prepared to simulate concentration levels expected during routine bioreactor fermentation processes. Near-IR spectra were collected from these solutions over the spectral range from 5000 to 4000 cm−1. This spectral information was used to build individual multivariate calibration models for each analyte. Models were constructed on the basis of partial least-squares regression of raw and Fourier filtered absorbance spectra. Each analyte could be detected selectively with mean percent errors of prediction ranging from 4 to 8%.

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