In this work, we electrochemically deposited self-doped polyanilines (SPANI) on the surface of carbon-nanoparticle (CNP) film, enhancing the superficial faradic reactions in supercapacitors and thus improving their performance. SPANI was electrodeposited on the CNP-film employing electropolymerization of aniline (AN) and o-aminobenzene sulfonic acid (SAN) comonomers in solution. Here, SAN acts in dual roles of a self-doped monomer while it also provides an acidic environment which is suitable for electropolymerization. The performance of SPANI−CNP-based supercapacitors significantly depends upon the mole ratio of AN/SAN. Supercapacitor performance was investigated by using cyclic voltammetry (CV), galvanostatic charge and discharge (GCD), and electrochemical impedance spectroscopy (EIS). The optimal performance of SPANI−CNP-based supercapacitor exists at AN/SAN ratio of 1.0, having the specific capacitance of 273.3 Fg⁻¹ at the charging current density of 0.5 Ag⁻¹.

Herein, we successfully synthesized a series of LaF₃:Yb³⁺/Er³⁺/Ho³⁺/Tm³⁺ upconversion nanoparticles (UCNPs) and LaF₃:Yb³⁺_0.20, Er³⁺_0.02@LaF₃:Yb³⁺_0.20 core/shell UCNPs by modifying the amount of NaOH and the reaction time. Hexagonal LaF₃ nanocrystals with uniform particle sizes and bright UC emissions were obtained. The crystal structures of the lanthanide-doped LaF₃ UCNPs were investigated using wide-angle X-ray diffraction. The morphologies and particle sizes of the nanocrystals were determined using transmission electron microscopy. The photoluminescence (PL) spectra of the LaF₃ nanocrystals could be tuned by altering the doping ratio of Er³⁺, Ho³⁺, and Tm³⁺. In addition, the PL intensities increased after coating the UCNP cores with an active shell. The fluorescence intensities of the UCNPs synthesized via a one-hour reaction with the addition of 2.5 or 5 mmol NaOH increased by up to 17 times compared with the sample prepared without the addition of NaOH. By modifying the doping ratio of Yb/Tm, UV-emissive LaF₃ nanocrystals were obtained. After surface modification by ligand exchange, the hydrophobic LaF₃:Yb³⁺_0.20, Er³⁺_0.02@LaF₃:Yb³⁺_0.20 core/shell UCNPs became water-dispersible. These colloid UCNPs could be utilized as a fluorescent probe for the detection of Hg²⁺ ions under 980 nm near-infrared irradiation.