An output-capacitorless low-dropout regulator (OCL-LDO) using a dual-active feedback frequency compensation (DAFFC) scheme with both transient and stability enhancement has been presented in this paper. The DAFFC scheme consists of two parallel active feedback paths, which creates two pole-zero pairs to effectively enhance the stability and transient response for the proposed OCL-LDO. Compared to the conventional single-path active-feedback frequency compensation method, the proposed DAFFC technique has provided one more design freedom with one more active feedback loop deployed and has been proved to be capable of obtaining better compensation effects with the same capacitor budget. Besides, the induced extra ac currents by the two active feedback loops have also enhanced the transient response of the proposed OCL-LDO. To substantiate the proposed DAFFC, a telescopic cascode output stage for error amplifier, and two on-chip compensation capacitors (5 and 1 pF, respectively) are needed. The proposed OCL-LDO has been implemented in 65-nm CMOS technology and the active chip area is 0.0105 mm ² . The output voltage is 0.8 V, and the minimum input voltage is 0.95 V at 100-mA loading current. The proposed OCL-LDO can work stably in a load range of 0 to 100 mA with 14-μA quiescent current.

By harnessing the phonon-assisted energy back transfer (EBT) from Er³⁺ to nearby Yb³⁺ ions, we obtain continuous multicolor (from green to red) UC fluorescence in the Gd₂O₃:Yb³⁺/Er³⁺ UCNPs.

Gd₂O₃:Tb is a promising candidate for use as a dual-modal contrast agent combining fluorescence imaging with MR imaging.

Gadolinium oxide (Gd₂O₃), which can be used as a T₁-weighted magnetic resonance imaging (MRI) contrast agent, has attracted intense attention in recent years. In this paper, ligand-free monoclinic Gd₂O₃ nanocrystals of 7.1 nm in diameter are synthesized by a simple and green approach, namely microsecond laser ablation of a gadolinium (Gd) target in deionized water. These nanocrystals obtain high r₁ relaxivity of 5.53 s⁻¹ mM⁻¹, and their low toxicity was demonstrated by the cell viability of S18 cells and apoptosis in RAW264.7 cells. In vitro and in vivo MR images show these particles to be good T₁-weighted MRI contrast agents. Base on the experimental results and theoretical analysis, we suggest that the purity of the Gd₂O₃ contributes to its high r₁ relaxivity value, while the low toxicity is due to its good crystallinity. These findings show that laser ablation in liquid (LAL) is a promising strategy to synthesize ligand-free monoclinic Gd₂O₃ nanocrystals for use as high efficient T₁-weighted MRI contrast agents.

Dualmodal contrast agents of rare earth doped gadolinium oxide (Gd₂O₃) nanoparticles with high spatial resolution for magnetic resonance imaging (MRI) and high sensitivity for fluorescence imaging have attracted intensive attention in biomedical imaging. However, the rare earth doped nanoparticles mentioned above have been so far synthesized by the hydrothermal method, which is a bottom-up method, requiring high purity chemical reagents and relying on the availability of the respective precursors and strict reaction conditions. Here, we propose a facile and environmentally friendly top-down technique to synthesize the rare earth doped-Gd₂O₃ nanocrystals at an ambient environment. Using this approach, we synthesize a series of Tm³⁺, Tb³⁺, and Eu³⁺ doped-Gd₂O₃ nanoparticle colloids and observe strong blue, green, and red visible fluorescence from the as-synthesized nanoparticle colloids. Cell confocal microscope images show that these synthesized nanoparticle colloids are good fluorescence imaging contrast agents. Taking Gd₂O₃:Eu³⁺ nanoparticles as an example, we evaluate their performance in MRI in vitro and in vivo. These results indicate that the synthesized rare earth doped-Gd₂O₃ nanocrystals can be used as MRI and fluorescence imaging dualmodal contrast agents. The developed technique is expected to be a general, facile and environmentally friendly strategy towards synthesizing rare earth doped nanoparticles for biomedical applications.