Thermal Reaction of Trimethylphosphine and Triethylphosphine on Cu(110)

Superparamagnetic Gold Nanoparticles Synthesized on Protein Particle Scaffolds for Cancer Theragnosis

Cancer theragnosis using a single multimodality agent is the next mainstay of modern cancer diagnosis, treatment, and management, but a clinically feasible agent with in vivo cancer targeting and theragnostic efficacy has not yet been developed. A new type of cancer theragnostic agent is reported, based on gold magnetism that is induced on a cancer-targeting protein particle carrier. Superparamagnetic gold-nanoparticle clusters (named SPAuNCs) are synthesized on a viral capsid particle that is engineered to present peptide ligands targeting a tumor cell receptor (TCR). The potent multimodality of the SPAuNCs is observed, which enables TCR-specific targeting, T₂ -weighted magnetic resonance imaging, and magnetic hyperthermia therapy of both subcutaneous and deep-tissue tumors in live mice under an alternating magnetic field. Furthermore, it is analytically elucidated how the magnetism of the SPAuNCs is sufficiently induced between localized and delocalized spins of Au atoms. In particular, the SPAuNCs show excellent biocompatibility without the problem of in vivo accumulation and holds promising potential as a clinically effective agent for cancer theragnosis.

Decomposition of dimethyl methylphosphonate on Pt, Au, and Au-Pt clusters supported on TiO2(110)

The decomposition of dimethyl methylphosphonate (DMMP) was studied by temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) on TiO(2)-supported Pt, Au, and Au-Pt clusters as well as on TiO(2)(110) itself. In agreement with previous work, TPD experiments for DMMP on TiO(2)(110) showed that methyl and methane were the main gaseous products. Multiple DMMP adsorption-reaction cycles on TiO(2)(110) demonstrated that active sites for DMMP decomposition were blocked after a single cycle, but some activity for methyl production was sustained even after five cycles. Furthermore, the activity of the TiO(2) surface could be regenerated by heating in O(2) at 800 K or heating in vacuum to 965 K to remove surface carbon and phosphorus, which are byproducts of DMMP decomposition. On 0.5 ML Pt clusters deposited on TiO(2)(110), TPD studies of DMMP reaction showed that CO and H(2) were the main gas products, with methyl and methane as minor products. The Pt clusters were more active than TiO(2) both in terms of the total amount of DMMP reaction and the ability to break C-H, P-O, and P-OCH(3) bonds in DMMP. However, the Pt clusters had no sustained activity for DMMP decomposition, since the product yields dropped to zero after a single adsorption-reaction cycle. This loss of activity is attributed to a combination of poisoning of active sites by surface phosphorus species and encapsulation of the Pt clusters by reduced titania after heating above 600 K due to strong metal support interactions (SMSI). On 0.5 ML Au clusters, CO and H(2) were also the main products detected in TPD experiments, in addition to methane and methyl produced from reaction on the support. The Au clusters were less active for DMMP decomposition to CO and H(2) as well as P-O bond scission, but surface phosphorus was removed from the Au clusters by desorption at approximately 900 K. Au-Pt bimetallic clusters on TiO(2)(110) were prepared by depositing 0.25 ML of Pt followed by 0.25 ML of Au, and the bimetallic surfaces exhibited activity intermediate between that of pure Pt and pure Au in terms of CO and H(2) desorption yields. However, there is evidence that the production of methane from DMMP decomposition occurs at Au-Pt sites.

Dimethyl methylphosphonate decomposition on Cu surfaces: supported Cu nanoclusters and films on TiO2(110)

The thermal decomposition of dimethyl methylphosphonate (DMMP), which is a simulant molecule for organophosphorus nerve agents, has been investigated on Cu clusters as well as on Cu films deposited on a TiO(2)(110) surface. Scanning tunneling microscopy studies were conducted to characterize the cluster sizes and surface morphologies of the deposited Cu clusters and films. Temperature-programmed desorption experiments demonstrated that the surface chemistry of DMMP is not sensitive to the size of the Cu clusters over the range studied in this work. DMMP reaction on an annealed 40 monolayer Cu film resulted in the desorption of H(2), methane, methyl, formaldehyde, methanol, and molecular DMMP, and reaction on the small (4.4 +/- 0.9 nm diameter, 1.8 +/- 0.6 nm height) and large (10.7 +/- 1.9 nm diameter, 4.8 +/- 1.0 nm height) Cu clusters generated similar products. Formaldehyde and methane production is believed to occur via a methoxy intermediate on the Cu surface. These products are favored on the higher coverage Cu films that completely cover the TiO(2) surface since competing reaction pathways on TiO(2) are suppressed. X-ray photoelectron spectroscopy studies showed that DMMP begins to decompose on the Cu clusters upon adsorption at room temperature and that atomic carbon, atomic phosphorus, and PO(x) remain on the surface after DMMP decomposition.