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Enhancement of Paramagnetic Relaxation by Photoexcited Gold Nanorods.

Wen T, Wamer WG, Subczynski WK, Hou S, Wu X, Yin JJ - Sci Rep (2016)

Bottom Line: It was shown that molecular oxygen plays the key role in this process.Our results demonstrate that ESR is a powerful tool for investigating the events following photoexcitation of GNRs.The novel light-controlled effects observed for GNRs on paramagnetic properties and activities of surrounding molecules have a number of significant applications where oxygen sensing and oxygen activity is important.

View Article: PubMed Central - PubMed

Affiliation: Division of Analytical Chemistry, Office of Regulatory Science, Center for Food Safety and Applied Nutrition, US Food and Drug Administration, College Park 20740, MD, USA.

ABSTRACT
Electron spin resonance (ESR) spectroscopy was used to investigate the switchable, light-dependent effects of gold nanorods (GNRs) on paramagnetic properties of nitroxide spin probes. The photoexcited GNRs enhanced the spin-spin and spin-lattice relaxations of nitroxide spin probes. It was shown that molecular oxygen plays the key role in this process. Our results demonstrate that ESR is a powerful tool for investigating the events following photoexcitation of GNRs. The novel light-controlled effects observed for GNRs on paramagnetic properties and activities of surrounding molecules have a number of significant applications where oxygen sensing and oxygen activity is important.

No MeSH data available.


Related in: MedlinePlus

Effects of molecular oxygen.(a) Oxygen dependence and cyclicity of LW changes for 100 μM 15N-PDT and 2.4 nM GNRs contained in a TPX capillary with on/off cycling of 808 nm laser irradiation (5 W). Following two cycles of exposure of air saturated solutions, samples were purged with N2, and then back to air saturated solutions. The shadows show that the light is on. (b) Schematic for oxygen activation around the photoexcited nanorod.
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f6: Effects of molecular oxygen.(a) Oxygen dependence and cyclicity of LW changes for 100 μM 15N-PDT and 2.4 nM GNRs contained in a TPX capillary with on/off cycling of 808 nm laser irradiation (5 W). Following two cycles of exposure of air saturated solutions, samples were purged with N2, and then back to air saturated solutions. The shadows show that the light is on. (b) Schematic for oxygen activation around the photoexcited nanorod.

Mentions: These viscosity effects demonstrate that photoexcited GNRs cause broadening of 15N-PDT’s LW predominately through Heisenberg spin exchange interactions. However, the spin system(s) interacting with 15N-PDT are not identified. Spin exchange interactions could result from direct interaction of the spin probe with GNRs or interactions with another paramagnetic species. It is well established that molecular oxygen, which in the electronic ground state () is paramagnetic, broadens the LW of spin probes through Heisenberg exchange interactions. Indeed, this is the basis for the use of ESR to measure concentrations of dissolved oxygen (ESR oximetry)7. To examine the role of dissolved oxygen, we compared the effects of photoexcited GNRs on 15N-PDT’s LW in air saturated solutions and in solutions purged with nitrogen (N2). As shown in Fig. 6, we observed that purging with N2 greatly reduces the effects of photoexcited GNRs on 15N-PDT’s LW without altering the on/off cycling associated with photoexcitation. The effects of purging with N2 were reversible. Equilibration of samples back to air, resulted in a return to the initially observed effects under air saturated conditions. Compared to LWs for unirradiated GNRs, LWs with photoexcited GNRs increased 31% in the air and only 12.5% after purging with N2. These results indicate that dissolved oxygen is involved in the SPR-driven effects of GNRs on the LW of 15N-PDT and that these effects were reversible. Similar reversibility by purging with N2 were observed using CTPO as a spin probe (Supplementary Fig. 6).


Enhancement of Paramagnetic Relaxation by Photoexcited Gold Nanorods.

Wen T, Wamer WG, Subczynski WK, Hou S, Wu X, Yin JJ - Sci Rep (2016)

Effects of molecular oxygen.(a) Oxygen dependence and cyclicity of LW changes for 100 μM 15N-PDT and 2.4 nM GNRs contained in a TPX capillary with on/off cycling of 808 nm laser irradiation (5 W). Following two cycles of exposure of air saturated solutions, samples were purged with N2, and then back to air saturated solutions. The shadows show that the light is on. (b) Schematic for oxygen activation around the photoexcited nanorod.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4829829&req=5

f6: Effects of molecular oxygen.(a) Oxygen dependence and cyclicity of LW changes for 100 μM 15N-PDT and 2.4 nM GNRs contained in a TPX capillary with on/off cycling of 808 nm laser irradiation (5 W). Following two cycles of exposure of air saturated solutions, samples were purged with N2, and then back to air saturated solutions. The shadows show that the light is on. (b) Schematic for oxygen activation around the photoexcited nanorod.
Mentions: These viscosity effects demonstrate that photoexcited GNRs cause broadening of 15N-PDT’s LW predominately through Heisenberg spin exchange interactions. However, the spin system(s) interacting with 15N-PDT are not identified. Spin exchange interactions could result from direct interaction of the spin probe with GNRs or interactions with another paramagnetic species. It is well established that molecular oxygen, which in the electronic ground state () is paramagnetic, broadens the LW of spin probes through Heisenberg exchange interactions. Indeed, this is the basis for the use of ESR to measure concentrations of dissolved oxygen (ESR oximetry)7. To examine the role of dissolved oxygen, we compared the effects of photoexcited GNRs on 15N-PDT’s LW in air saturated solutions and in solutions purged with nitrogen (N2). As shown in Fig. 6, we observed that purging with N2 greatly reduces the effects of photoexcited GNRs on 15N-PDT’s LW without altering the on/off cycling associated with photoexcitation. The effects of purging with N2 were reversible. Equilibration of samples back to air, resulted in a return to the initially observed effects under air saturated conditions. Compared to LWs for unirradiated GNRs, LWs with photoexcited GNRs increased 31% in the air and only 12.5% after purging with N2. These results indicate that dissolved oxygen is involved in the SPR-driven effects of GNRs on the LW of 15N-PDT and that these effects were reversible. Similar reversibility by purging with N2 were observed using CTPO as a spin probe (Supplementary Fig. 6).

Bottom Line: It was shown that molecular oxygen plays the key role in this process.Our results demonstrate that ESR is a powerful tool for investigating the events following photoexcitation of GNRs.The novel light-controlled effects observed for GNRs on paramagnetic properties and activities of surrounding molecules have a number of significant applications where oxygen sensing and oxygen activity is important.

View Article: PubMed Central - PubMed

Affiliation: Division of Analytical Chemistry, Office of Regulatory Science, Center for Food Safety and Applied Nutrition, US Food and Drug Administration, College Park 20740, MD, USA.

ABSTRACT
Electron spin resonance (ESR) spectroscopy was used to investigate the switchable, light-dependent effects of gold nanorods (GNRs) on paramagnetic properties of nitroxide spin probes. The photoexcited GNRs enhanced the spin-spin and spin-lattice relaxations of nitroxide spin probes. It was shown that molecular oxygen plays the key role in this process. Our results demonstrate that ESR is a powerful tool for investigating the events following photoexcitation of GNRs. The novel light-controlled effects observed for GNRs on paramagnetic properties and activities of surrounding molecules have a number of significant applications where oxygen sensing and oxygen activity is important.

No MeSH data available.


Related in: MedlinePlus