Enhancing the electronic and optical properties of the metal/semiconductor NbS2/BSe nanoheterostructure towards advanced electronics

Metal-semiconductor (M-S) contacts play a vital role in advanced applications, serving as crucial components in ultracompact devices and exerting a significant impact on overall device performance. Here, in this work, we design a M-S nanoheterostructure between a metallic NbS2 monolayer and a semiconducting BSe monolayer using first-principles prediction. The stability of such an M-S nanoheterostructure is verified and its electronic and optical properties are also considered. Our results indicate that the NbS2/BSe nanoheterostructure is structurally, mechanically and thermally stable. The formation of the NbS2/BSe heterostructure leads to the generation of a Schottky contact with the Schottky barrier ranging from 0.36 to 0.51 eV, depending on the stacking configurations. In addition, the optical absorption coefficient of the NbS2/BSe heterostructure can reach up to 5 × 105 cm-1 at a photon energy of about 5 eV, which is still greater than that in the constituent NbS2 and BSe monolayers. This finding suggests that the formation of the M-S NbS2/BSe heterostructure gives rise to an enhancement in the optical absorption of both NbS2 and BSe monolayers. Notably, the tunneling probability and the contact tunneling-specific resistivity at the interface of the NbS2/BSe heterostructure are low, indicating its applicability in emerging nanoelectronic devices, such as Schottky diodes and field-effect transistors. Our findings offer valuable insights for the practical utilization of electronic devices based on the NbS2/BSe heterostructure.

High-efficiency energy transfer in the strong orange-red-emitting phosphor CeO2:Sm3+, Eu3

High-efficiency energy transfer (ET) from Sm3+ to Eu3+ leads to dominant red emission in Sm3+, Eu3+ co-doped single-phase cubic CeO2 phosphors. In this work, a series of Sm3+ singly and Sm3+/Eu3+ co-doped CeO2 cubic phosphors was successfully synthesized by solution combustion followed by heat treatment at 800 °C in air. The crystal structure, morphology, chemical element composition, and luminescence properties of the obtained phosphors were investigated using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and photoluminescence analysis. Under 360 nm excitation, the Sm3+ singly doped CeO2 phosphor emitted strong yellow-red light at 573 nm (4G5/2-6H5/2) and 615 nm (4G5/2-6H7/2). Meanwhile, the CeO2:Sm3+, Eu3+ phosphors showed the emission characteristic of both Sm3+ and Eu3+, with the highest emission intensity at 631 nm. The emission intensity of Sm3+ decreased with increasing Eu3+ content, suggesting the ET from Sm3+ to Eu3+ in the CeO2:Sm3+, Eu3+ phosphors. The decay kinetics of the 4G5/2-6H5/2 transition of Sm3+ in the CeO2:Sm3+, Eu3+ phosphors were investigated, confirming the high-efficiency ET from Sm3+ to Eu3+ (reached 84%). The critical distance of energy transfer (RC = 13.7 Å) and the Dexter theory analysis confirmed the ET mechanism corresponding to the quadrupole-quadrupole interaction. These results indicate that the high-efficiency ET from Sm3+ to Eu3+ in CeO2:Sm3+, Eu3+ phosphors is an excellent strategy to improve the emission efficiency of Eu3+.

Enhancing acid orange II degradation in ozonation processes with CaFe2O4 nanoparticles as a heterogeneous catalyst

This study used CaFe2O4 nanoparticles as a catalyst for ozonation processes to degrade Acid Orange II (AOII) in aqueous solution. The study compared heterogeneous catalytic ozonation (CaFe2O4/O3) with ozone treatment alone (O3) at different pH values (3-11), catalyst dosages (0.25-2.0 g L-1), and initial AOII concentrations (100-500 mg L-1). The O3 alone and CaFe2O4/O3 systems nearly completely removed AOII's color. In the first 5 min, O3 alone had a color removal efficiency of 75.66%, rising to 92% in 10 min, whereas the CaFe2O4/O3 system had 81.49%, 94%, and 98% after 5, 10, and 20 min, respectively. The O3 and CaFe2O4/O3 systems degrade TOC most efficiently at pH 9 and better with 1.0 g per L CaFe2O4. TOC removal effectiveness reduced from 85% to 62% when the initial AOII concentration increased from 100 to 500 mg L-1. The study of degradation kinetics reveals a pseudo-first-order reaction mechanism significantly as the solution pH increased from 3 to 9. Compared to the O3 alone system, the CaFe2O4/O3 system has higher k values. At pH 9, the k value for the CaFe2O4/O3 system is 1.83 times higher than that of the O3 alone system. Moreover, increasing AOII concentration from 100 mg L-1 to 500 mg L-1 subsequently caused a decline in the k values. The experimental data match pseudo-first-order kinetics, as shown by R2 values of 0.95-0.99. AOII degradation involves absorption, ozone activation, and reactive species production based on the existence of CaO and FeO in the CaFe2O4 nanocatalyst. This catalyst can be effectively recycled multiple times.

A glucose-assisted redox hydrothermal route to prepare a Mn-doped CeO2 catalyst for the total catalytic oxidation of VOCs

In this study, a novel glucose-assisted redox hydrothermal method has been presented to prepare an Mn-doped CeO₂ catalyst (denoted as Mn-CeO₂-R) for the first time. The obtained catalyst contains uniform nanoparticles with a small crystallite size, a large mesopore volume, and rich active surface oxygen species. Such features collectively contribute to improving the catalytic activity for the total catalytic oxidation of methanol (CH₃OH) and formaldehyde (HCHO). Interestingly, the large mesopore volume feature of the Mn-CeO₂-R samples could be considered an essential factor to eliminate the diffusion limit, favoring the total oxidation of toluene (C₇H₈) at high conversion. Therefore, the Mn-CeO₂-R catalyst outperforms both bare CeO₂ and conventional Mn-CeO₂ catalysts with T ₉₀ values of 150 °C and 178 °C for HCHO and CH₃OH, respectively, and 315 °C for C₇H₈, at a high GHSV of 60 000 mL g^-1 h^-1. Such robust catalytic activities signify a potential utilization of Mn-CeO₂-R for the catalytic oxidation of volatile organic compounds (VOCs).

Ultrasonic-assisted synthesis of magnetic recyclable Fe3O4/rice husk biochar based photocatalysts for ciprofloxacin photodegradation in aqueous solution

In this work, a new facile one-spot method has been designed to fabricate a magnetic recyclable Fe₃O₄/rice husk biochar photocatalyst (FBP) for the removal of Ciprofloxacin (CIP) in aqueous solution. This method combines ultrasonic-assisted impregnation and precipitation, which can overcome the difficulties of long-time reactions, complex procedures, and extreme condition requirements. The successful fabrication of the Fe₃O₄/biochar material has been proven by a series of material characterization techniques, including X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Raman, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), and vibrating sample magnetometer (VSM). Moreover, the as-product FBP exhibited the excellent ability of photodegrading CIP and the possibility of magnetic recovery from the aqueous solution, suggesting a potential solution for removing antibiotic pollutants in environmental remediation.