The surfaces of six biologically interesting calcium phosphate (CaP) phases (hydroxyapatite, dibasic calcium phosphate dihydrate, dibasic calcium phosphate, monobasic calcium phosphate, beta-tribasic calcium phosphate, octacalcium phosphate) have been examined by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The intensity of an O(1s) shake-up satellite correlates with the phosphate oxygen content. Together with the Ca/P and O/Ca XPS peak ratios, this feature helps provide identification of the CaP phase(s) present in the surface of unknown samples and establish their mole fractions, as proven with a bone sample. Contributions from carbonate impurities can be quantified using its C(1s) peak at 279.9 eV and subtracted from the O(1s) line shape to aid identification. Principal component analysis (PCA) has been applied successfully to analyze TOF-SIMS spectra of these six CaP phases. Multivariate analysis can help differentiate these CaP phases using the first two PCs, which are dominated by the relative intensities of only a few key ions: PO3-, O-, Ca+, CaOH+, PO2-, and OH-.

A novel semiconductor–rubber–semiconductor triblock copolymer has been designed and prepared according to the principle of thermoplastic elastomers (TPEs). It behaves as a TPE and exhibits good electrical properties.

The attachment of linear poly(ethylene glycol) (PEG) molecules (MW = 2000−5000) to gold surfaces via orthopyridyl−disulfide (OPSS) terminal groups has been studied with X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF−SIMS), and surface plasmon resonance (SPR). The molecules examined included a PEG molecule terminated with a methoxy group and derivatized with an OPSS group at the other end (M-PEG-OPSS), a PEG molecule derivatized with OPSS at both ends (PEG-(OPSS)2), and a PEG derivatized with an N-hydroxysuccinimide group at one end and an OPSS group at the other (NHS-PEG-OPSS). Exposure of gold to aqueous solutions of these resulted in immobilization via gold−thiolate bonds from the OPSS disulfide groups. The resulting mixed PEG−/OPS− thiolate monolayers were not always in 1:1 ratio. Most of the PEG-(OPSS)2 molecules formed gold−thiolate bonds at both ends, but some left a free, intact OPSS group. For biosensor applications, this or the free NHS groups in the NHS-PEG-OPSS films can be used to immobilize biomolecules with accessible cysteines or lysines via formation of disulfide bonds or amide bonds, respectively. The PEG films formed by M-PEG-OPSS and PEG-(OPSS)2 resist the adsorption of albumin.

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