Facile Synthesis of Fe@C Loaded on g-C3N4 for CO2 Electrochemical Reduction to CO with Low Overpotential

Electrochemical CO₂ reduction has been acknowledged as a hopeful tactic to alleviate environmental and global energy crises. Herein, we designed an Fe@C/g-C₃N₄ heterogeneous nanocomposite material by a simple one-pot method, which we applied to the electrocatalytic CO₂ reduction reaction (ECR). Our optimized 20 mg-Fe@C/g-C₃N₄-1100 catalyst displays excellent performance for the ECR and a maximum Faradaic efficiency (FE) of 88% with a low overpotential of -0.38 V vs. RHE. The Tafel slope reveals that the first electron transfer, which involves a surface-adsorbed *COOH intermediate, is the rate-determining step for 20 mg-Fe@C/C₃N₄-1100 during the ECR. More precisely, the coordinating capability of the g-C₃N₄ framework and Fe@C species as a highly active site promote the intermediate product transmission. These results indicate that the combination of temperature adjustment and precursor optimization is key to facilitating the ECR of an iron-based catalyst.

Biocompatible Ni-doped CdSe/ZnS semiconductor nanocrystals for cellular imaging and sorting

Quantum dots with chemical composition QD CdSe / ZnS _ Ni 650 are successfully synthesized by the hydrothermal method using chemical precipitation. Nanocrystalline phase of nanostructures are isolated and characterized using XRD. The mean crystalline size was 9.0±2.0 nm with core/shell Ni-dopant of the Quantum dot diameter. The ferromagnetic data reveal the magnetic behavior of QD CdSe / ZnS _ Ni 650 . The optical absorption measurement of these QDs in the UV-vis range 200-800 nm band gap value of 2.11 eV for QD CdSe / ZnS _ Ni 650 . This means that pure QD CdSe 650 and QD CdSe / ZnS _ Ni 650 have a redshift of when compared to bulk CdSe. These QD CdSe / ZnS _ Ni 650 where successfully uptake by the cell lines include HELA and MCF-7 for bioimaging and sorting applications.

Computational studies of the electronic structure of copper-doped ZnO quantum dots

Copper-doped ZnO quantum dots (QDs) have attracted substantial interest. The electronic structure and optical and magnetic properties of Cu³⁺(d⁸)-, Cu²⁺(d⁹)-, and Cu⁺(d¹⁰)-doped ZnO QDs with sizes up to 1.5 nm are investigated using the GGA+U approximation, with the +U corrections applied to d (Zn), p(O), and d(Cu) orbitals. Taking +Us parameters, as optimized in previous bulk calculations, we obtain the correct band structure of ZnO QDs. Both the description of electronic structure and thermodynamic charge state transitions of Cu in ZnO QDs agree with the results of bulk calculations due to the strong localization of Cu defect energy levels. Atomic displacements around Cu are induced by strong Jahn-Teller distortion and affect Kohn-Sham energies and thermodynamic transition levels. The average bond length of Cu-O and the defect structure are crucial factors influencing the electronic properties of Cu in ZnO QDs. The analysis of the optical properties of Cu in ZnO QDs is reported. The GGA+U results, compared with the available experimental data, support Dingle's model [Phys. Rev. Lett. 23, 579 (1969)], in which the structured green luminescence observed in bulk and nanocrystals originates from the [(Cu⁺, hole) → Cu²⁺] transition. We also examine the magnetic interaction between the copper pair for two charge states: 0 and +2, and four positions relative to the center of QDs. Ferromagnetic interaction between ions is obtained for every investigated configuration. The magnitude of ferromagnetism increases for positive charge defects due to the strong hybridization of the d(Cu) and p(O) states.

Aptamer Turn-On SERS/RRS/Fluorescence Tri-mode Platform for Ultra-trace Urea Determination Using Fe/N-Doped Carbon Dots

Sensitive and selective methods for the determination of urea in samples such as dairy products are important for quality control and health applications. Using ammonium ferric citrate as a precursor, Fe/N-codoped carbon dots (CD_FeN) were prepared by a hydrothermal procedure and characterized in detail. CD_FeN strongly catalyzes the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H₂O₂ to turn on an indicator molecular reaction, forming an oxidized tetramethylbenzidine (TMB_ox) probe with surface-enhanced Raman scattering, resonance Rayleigh scattering, and fluorescence (SERS, RRS, and FL) signals at 1,598 cm⁻¹, 370 nm, and 405 nm, respectively. The urea aptamer (Apt) can turn off the indicator reaction to reduce the tri-signals, and the addition of urea turns on the indicator reaction to linearly enhance the SERS/RRS/FL intensity. Thus, a novel Apt turn-on tri-mode method was developed for the assay determination of ultra-trace urea with high sensitivity, good selectivity, and accuracy. Trace adenosine triphosphate and estradiol can also be determined by the Apt-CD_FeN catalytic analytical platform.

The cation-anion co-exchange in CsPb1-x Fe x (Br1-y Cl y )3 nanocrystals prepared using a hot injection method

All inorganic perovskite nanocrystals (NCs) have wide practical applications for their remarkable optoelectronic properties. To obtain blue-emitting perovskites with high photoluminescence quantum yield and room-temperature ferromagnetism, CsPb_1-x Fe _x (Br_1-y Cl _y )₃ NCs were synthesized using a hot injection method. The effects of the cation-anion co-exchange on the structural, luminescent and magnetic properties of CsPbBr₃ NCs were studied by X-ray diffraction spectroscopy, photoluminescence spectroscopy, transmission electron microscopy, field emission scanning electron microscopy, and vibrating sample magnetometer. The results indicated that there was cation-anion co-exchange in CsPb_1-x Fe _x (Br_1-y Cl _y )₃ NCs, while the band-edge energies and PLQY were mainly affected by the anion exchange. The ferromagnetism of CsPb_1-x Fe _x (Br_1-y Cl _y )₃ NCs had been observed at room temperature, and there was an increase in saturation magnetization with increasing Fe concentration.

Graphene-Induced Room Temperature Ferromagnetism in Cobalt Nanoparticles Decorated Graphene Nanohybrid

Control over the magnetic interactions in magnetic nanoparticles (MNPs) is a crucial issue to the future development of nanometer-sized integrated "spintronic" applications. Here, we have developed a nanohybrid structure to achieve room temperature ferromagnetism, via a facile, effective, and reproducible solvothermal synthesis method. The plan has been put onto cobalt (Co) NPs, where the growth of Co NPs on the surface of reduced graphene oxide (rGO) nanosheets switches the magnetic interactions from superparamagnetic to ferromagnetic at room temperature. Switching-on ferromagnetism in this nanohybrid may be due to the hybridization between unsaturated 2p_z orbitals of graphene and 3d orbitals of Co, which promotes ferromagnetic long-range ordering. The ferromagnetic behavior of Co-rGO nanohybrid makes it excellent material in the field of spintronics, catalysis, and magnetic resonance imaging.