Limits...
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 photoexcited GNRs on relaxation times.(a) UV-vis-NIR extinction spectrum of CTAB coated GNRs dispersed in water. Inset is a typical transmission electron microscopy (TEM) image of the prepared GNRs. (b) ESR spectra of 100 μM 15N-PDT and 2.4 nM GNRs exposed to different powers of the 808 nm laser for 10 min. The LWs are 0.27, 0.32, 0.39, 0.43 G for 0, 1.5, 3, 5 W, respectively. (c) LWs of ESR spectra for samples having different concentrations of GNRs and 100 μM 15N-PDT during irradiation with an 808 nm laser (5 W) for 10 min. (d) Microwave power saturation curve for 100 μM 15N-PDT in the absence and presence of 2.4 nM GNRs at 37 °C. Samples were in the dark or irradiated with an 808 nm laser (5 W). The saturating (P1/2) power is shown as circle indicated. Note that the molar concentration of GNRs here means the concentration of nanoparticles (See Supplementary Information). The power in the (b) indicates the power of laser beam, while the power in the (d) indicates the microwave power of the ESR spectrometer.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4829829&req=5

f1: Effects of photoexcited GNRs on relaxation times.(a) UV-vis-NIR extinction spectrum of CTAB coated GNRs dispersed in water. Inset is a typical transmission electron microscopy (TEM) image of the prepared GNRs. (b) ESR spectra of 100 μM 15N-PDT and 2.4 nM GNRs exposed to different powers of the 808 nm laser for 10 min. The LWs are 0.27, 0.32, 0.39, 0.43 G for 0, 1.5, 3, 5 W, respectively. (c) LWs of ESR spectra for samples having different concentrations of GNRs and 100 μM 15N-PDT during irradiation with an 808 nm laser (5 W) for 10 min. (d) Microwave power saturation curve for 100 μM 15N-PDT in the absence and presence of 2.4 nM GNRs at 37 °C. Samples were in the dark or irradiated with an 808 nm laser (5 W). The saturating (P1/2) power is shown as circle indicated. Note that the molar concentration of GNRs here means the concentration of nanoparticles (See Supplementary Information). The power in the (b) indicates the power of laser beam, while the power in the (d) indicates the microwave power of the ESR spectrometer.

Mentions: The UV-vis-NIR extinction spectrum of cetyltrimethylammonium bromide (CTAB) coated GNRs in water has two extinction maxima at 511 nm and 810 nm, resulting from exciting the GNR’s transverse and longitudinal surface plasmons, respectively (Fig. 1a). These CTAB coated GNRs have an average length of 60.6 ± 7.5 nm and an aspect ratio of 4 (Fig. 1a, insert). Changes in the ESR spectra of 15N-PDT sensitively report changes in paramagnetic interactions with their chemical environment. These spectral changes are induced by factors which alter the rate of collisions or strength of interactions between 15N-PDT and other paramagnetic molecules. The value of 15N-PDT as a spin probe is evident from its many applications, including its use in ESR oximetry for measuring levels of molecular oxygen. Here, 15N-PDT was used to probe the effects of photoexcited GNRs on chemical species in the surrounding medium. We observed that the LW of 15N-PDT significantly increased during photoexcitation of the GNR’s longitudinal SPR using an 808 nm laser (Fig. 1b). The LW of 15N-PDT in the suspension of GNRs increased from 0.26 ± 0.01 G to 0.43 ± 0.01 G with 808 nm laser (5 W) irradiation, and was dependent on the power of the laser. Effects on the LW of 15N-PDT were also closely dependent on the concentration of GNRs (Fig. 1c) and their extinction spectrum (Supplementary Fig. 1), indicating the role of GNRs’ SPR on the LW of 15N-PDT. Another spin probe (CTPO) was used to confirm the generality of the observed effect. We demonstrated that photoexcitation of GNRs results in the reduction in the super hyperfine structure of CPTO and dependence on the power of the incident laser radiation (Supplementary Fig. 2 and Supplementary Fig. 3).


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 photoexcited GNRs on relaxation times.(a) UV-vis-NIR extinction spectrum of CTAB coated GNRs dispersed in water. Inset is a typical transmission electron microscopy (TEM) image of the prepared GNRs. (b) ESR spectra of 100 μM 15N-PDT and 2.4 nM GNRs exposed to different powers of the 808 nm laser for 10 min. The LWs are 0.27, 0.32, 0.39, 0.43 G for 0, 1.5, 3, 5 W, respectively. (c) LWs of ESR spectra for samples having different concentrations of GNRs and 100 μM 15N-PDT during irradiation with an 808 nm laser (5 W) for 10 min. (d) Microwave power saturation curve for 100 μM 15N-PDT in the absence and presence of 2.4 nM GNRs at 37 °C. Samples were in the dark or irradiated with an 808 nm laser (5 W). The saturating (P1/2) power is shown as circle indicated. Note that the molar concentration of GNRs here means the concentration of nanoparticles (See Supplementary Information). The power in the (b) indicates the power of laser beam, while the power in the (d) indicates the microwave power of the ESR spectrometer.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Effects of photoexcited GNRs on relaxation times.(a) UV-vis-NIR extinction spectrum of CTAB coated GNRs dispersed in water. Inset is a typical transmission electron microscopy (TEM) image of the prepared GNRs. (b) ESR spectra of 100 μM 15N-PDT and 2.4 nM GNRs exposed to different powers of the 808 nm laser for 10 min. The LWs are 0.27, 0.32, 0.39, 0.43 G for 0, 1.5, 3, 5 W, respectively. (c) LWs of ESR spectra for samples having different concentrations of GNRs and 100 μM 15N-PDT during irradiation with an 808 nm laser (5 W) for 10 min. (d) Microwave power saturation curve for 100 μM 15N-PDT in the absence and presence of 2.4 nM GNRs at 37 °C. Samples were in the dark or irradiated with an 808 nm laser (5 W). The saturating (P1/2) power is shown as circle indicated. Note that the molar concentration of GNRs here means the concentration of nanoparticles (See Supplementary Information). The power in the (b) indicates the power of laser beam, while the power in the (d) indicates the microwave power of the ESR spectrometer.
Mentions: The UV-vis-NIR extinction spectrum of cetyltrimethylammonium bromide (CTAB) coated GNRs in water has two extinction maxima at 511 nm and 810 nm, resulting from exciting the GNR’s transverse and longitudinal surface plasmons, respectively (Fig. 1a). These CTAB coated GNRs have an average length of 60.6 ± 7.5 nm and an aspect ratio of 4 (Fig. 1a, insert). Changes in the ESR spectra of 15N-PDT sensitively report changes in paramagnetic interactions with their chemical environment. These spectral changes are induced by factors which alter the rate of collisions or strength of interactions between 15N-PDT and other paramagnetic molecules. The value of 15N-PDT as a spin probe is evident from its many applications, including its use in ESR oximetry for measuring levels of molecular oxygen. Here, 15N-PDT was used to probe the effects of photoexcited GNRs on chemical species in the surrounding medium. We observed that the LW of 15N-PDT significantly increased during photoexcitation of the GNR’s longitudinal SPR using an 808 nm laser (Fig. 1b). The LW of 15N-PDT in the suspension of GNRs increased from 0.26 ± 0.01 G to 0.43 ± 0.01 G with 808 nm laser (5 W) irradiation, and was dependent on the power of the laser. Effects on the LW of 15N-PDT were also closely dependent on the concentration of GNRs (Fig. 1c) and their extinction spectrum (Supplementary Fig. 1), indicating the role of GNRs’ SPR on the LW of 15N-PDT. Another spin probe (CTPO) was used to confirm the generality of the observed effect. We demonstrated that photoexcitation of GNRs results in the reduction in the super hyperfine structure of CPTO and dependence on the power of the incident laser radiation (Supplementary Fig. 2 and Supplementary Fig. 3).

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