We have designed and synthesized NaGdF4：Nd^3＋, Yb^3＋, Tm^3＋. magnetic nano- phosphors with combined dual-mode downconversion （DC） and upconversion （UC） photoluminescence upon 800 run excitation. Hexagonal-phas...We have designed and synthesized NaGdF4：Nd^3＋, Yb^3＋, Tm^3＋. magnetic nano- phosphors with combined dual-mode downconversion （DC） and upconversion （UC） photoluminescence upon 800 run excitation. Hexagonal-phase NaGdF4：Nd^3＋, Yb^3＋, Tm^3＋ nanocrystals （NCs） with an average size of 21 nm were synthesized using a solvothermal approach. Nd^3＋, Yb^3＋, Tm^3＋ triple-doped NaGdF4 NCs exhibit a broad range of photoluminescence peaks covering a near infrared first/second window （860-900, 1,000, and 1,060 nm）, and visible emission including blue （475 nm）, green （520 and 542 nm） and yellow （587 nm） after excitation at 800 nm. A mechanism involving circulation of energy over Gd^3＋ sublattices as bridge ions and final trapping by the initial activator ions （Nd^3＋） has been proposed. Penetration depth studies indicate that NIR emission is easily detected even at a large tissue thickness of 10 mm. These paramagnetic nanophosphors demonstrate a large magnetization value of 1.88 emu/g at 20 kOe and longitudinal relaxivity value of 1.2537 mM-1.S-1 as a Tl-weighted magnetic resonance imaging contrast agent. These NaGdF4：Nd^3＋, Yb^3＋ Tm^3＋ NCs are promising for applications in biological and magnetic resonance imaging.展开更多
Superparamagnetic iron oxide （SPIO） nanoparticle clusters are one unique form which can enhance magnetic relaxivity and improve the magnetic resonance imaging contrast at the same iron concentration, comparing to si...Superparamagnetic iron oxide （SPIO） nanoparticle clusters are one unique form which can enhance magnetic relaxivity and improve the magnetic resonance imaging contrast at the same iron concentration, comparing to single SPIO nanoparticles. Controlling of cluster size and other structural parameters have drawn great interests in this field to further improve their magnetic properties. In this study, we investigated how the interparticle distance （also known as neighbor distance） of SP10 nanocrystals within clusters affect their magnetic relaxation behaviors. To adjust the neighbor distance, different amount of cholesterol （CHO） was chosen as model spacers embedded into SPIO nanocluster systems with the help of amphiphilic diblock copolymer poly（ethylene glyco）-polyester. Small- angle X-ray scattering was applied to quantify the neighbor distance of SPIO clusters. The results demonstrated that the averaged SPIO nanocrystal neighbor distance of nan- oclusters increased with higher amount of added CHO. Moreover, these SPIO nanocrystal clusters had the promi- nent magnetic relaxation properties. Simultaneously, con- trolling of SPIO nanocrystal neighbor distance can regulate the saturation magnetization （Ms） and magnetic resonance （MR） T2 relaxation of the aggregation, and ultimately obtain better MR contrast effects with decreased neighbor distance.展开更多
文摘We have designed and synthesized NaGdF4：Nd^3＋, Yb^3＋, Tm^3＋. magnetic nano- phosphors with combined dual-mode downconversion （DC） and upconversion （UC） photoluminescence upon 800 run excitation. Hexagonal-phase NaGdF4：Nd^3＋, Yb^3＋, Tm^3＋ nanocrystals （NCs） with an average size of 21 nm were synthesized using a solvothermal approach. Nd^3＋, Yb^3＋, Tm^3＋ triple-doped NaGdF4 NCs exhibit a broad range of photoluminescence peaks covering a near infrared first/second window （860-900, 1,000, and 1,060 nm）, and visible emission including blue （475 nm）, green （520 and 542 nm） and yellow （587 nm） after excitation at 800 nm. A mechanism involving circulation of energy over Gd^3＋ sublattices as bridge ions and final trapping by the initial activator ions （Nd^3＋） has been proposed. Penetration depth studies indicate that NIR emission is easily detected even at a large tissue thickness of 10 mm. These paramagnetic nanophosphors demonstrate a large magnetization value of 1.88 emu/g at 20 kOe and longitudinal relaxivity value of 1.2537 mM-1.S-1 as a Tl-weighted magnetic resonance imaging contrast agent. These NaGdF4：Nd^3＋, Yb^3＋ Tm^3＋ NCs are promising for applications in biological and magnetic resonance imaging.
基金supported by the National Key Basic Research Program of China (2013CB933903)the National High Technology R&D Program of China (2012BAI23B08)the National Natural Science Foundation of China (20974065, 51173117 and 50830107)
文摘Superparamagnetic iron oxide （SPIO） nanoparticle clusters are one unique form which can enhance magnetic relaxivity and improve the magnetic resonance imaging contrast at the same iron concentration, comparing to single SPIO nanoparticles. Controlling of cluster size and other structural parameters have drawn great interests in this field to further improve their magnetic properties. In this study, we investigated how the interparticle distance （also known as neighbor distance） of SP10 nanocrystals within clusters affect their magnetic relaxation behaviors. To adjust the neighbor distance, different amount of cholesterol （CHO） was chosen as model spacers embedded into SPIO nanocluster systems with the help of amphiphilic diblock copolymer poly（ethylene glyco）-polyester. Small- angle X-ray scattering was applied to quantify the neighbor distance of SPIO clusters. The results demonstrated that the averaged SPIO nanocrystal neighbor distance of nan- oclusters increased with higher amount of added CHO. Moreover, these SPIO nanocrystal clusters had the promi- nent magnetic relaxation properties. Simultaneously, con- trolling of SPIO nanocrystal neighbor distance can regulate the saturation magnetization （Ms） and magnetic resonance （MR） T2 relaxation of the aggregation, and ultimately obtain better MR contrast effects with decreased neighbor distance.
