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In this study, carbon-quantum-dot (CQD)-decorated TiO2 was prepared using an ultrasonic doping method and applied in the photocatalytic degradation of naphthalene under sunlight irradiation. The CQDs were synthesized from a typical macroalgae via diluted sulfuric acid pretreatment and hydrothermal synthesis using an optimal design, i.e., 3 wt% and 200 °C, respectively. The CQD/TiO2 composite remarkably enhanced the photocatalytic activity. The degradation of naphthalene under a visible light environment indicated that there is a synergistic mechanism between the CQDs and TiO2, in which the generation of reactive oxygen species is significantly triggered; in addition, the N that originated from the macroalgae accelerated the photocatalytic efficiency. Kinetic analysis showed that the photocatalytic behavior of the CQD/TiO2 composite followed a pseudo-first-order equation. Consequently, our combined experimental approach not only provides a facile pretreatment process for bio-CQDs synthesis, but also delivers a suitable TiO2 photocatalyst for the visible environment along with critical insights into the development of harmful macroalgae resources. [ABSTRACT FROM AUTHOR]

High-symmetry transition-metal dichalcogenides (TMDs) have garnered substantial attention in the fields of sensors, optoelectronics, and valleytronics. However, the inherent C3 rotational symmetry of TMDs engenders highly isotropic properties, impeding their further technological progress. To overcome this limitation, we embarked on a study to investigate the effects of isotropic/anisotropic heterostructures engineering on WS2, aiming to break its C3 rotational symmetry. In this work, we designed and fabricated heterostructures composed of WS2 and ReS2 layers. Our comprehensive investigations revealed a remarkable emergence of anisotropic characteristics in excitons originating from the WS2 layers within the engineered WS2/ReS2 heterostructures. Moreover, we observed an enhancement in the valley polarizations of WS2 layers within the heterostructures, which is attributed to the reduced intervalley scattering facilitated by the WS2/ReS2 heterostructure configuration. This observation indicates the potential for leveraging heterostructure engineering to tailor and optimize anisotropic devices, thereby opening promising avenues for future applications in various technological domains. [ABSTRACT FROM AUTHOR]

Moiré superlattices in van der Waals structures have emerged as a powerful platform for studying the novel quantum properties of two-dimensional materials. The periodic moiré patterns generated by these structures lead to the formation of flat mini-bands, which alter the electronic energy bands of the material. The resulting flat electronic bands can greatly enhance strong correlative interactions between electrons, leading to the emergence of exotic quantum phenomena, including moiré phonons and moiré excitons. While extensive research has been conducted on the exotic quantum phenomena in twisted bilayers of transition metal dichalcogenides (TMDs), and the regulatory effect of stacked layers on moiré excitons remains unexplored. In this study, we report the fabrication of a twisted WSe2/WSe2/WSe2 homotrilayer with two twist angles and investigate the influence of stacked layers on moiré excitons. Our experiments reveal multiple moiré exciton splitting peaks in the twisted trilayer, with moiré potential depths of 78 and 112 meV in the bilayer and trilayer homostructures, respectively. We also observed the splitting of the moiré excitons at 90 K, indicating the presence of a deeper moiré potential in the twisted trilayer. Moreover, we demonstrate that stacked layers can tune the moiré excitons by manipulating temperature, laser power, and magnetic field. Our results provide a new physical model for studying moiré superlattices and their quantum properties, which could potentially pave the way for the development of quantum optoelectronics. [ABSTRACT FROM AUTHOR]

Exploiting the valley degrees of freedom as information carriers provides new opportunities for the development of valleytronics. Monolayer transition metal dichalcogenides (TMDs) with broken space-inversion symmetry exhibit emerging valley pseudospins, making them ideal platforms for studying valley electronics. However, intervalley scattering of different energy valleys limits the achievable degree of valley polarization. Here, we constructed WSe2/yttrium iron garnet (YIG) heterostructures and demonstrated that the interfacial magnetic exchange effect on the YIG magnetic substrate can enhance valley polarization by up to 63%, significantly higher than that of a monolayer WSe2 on SiO2/Si (11%). Additionally, multiple sharp exciton peaks appear in the WSe2/YIG heterostructures due to the strong magnetic proximity effect at the magnetic–substrate interface that enhances exciton emission efficiency. Moreover, under the effect of external magnetic field, the magnetic direction of the magnetic substrate enhances valley polarization, further demonstrating that the magnetic proximity effect regulates valley polarization. Our results provide a new way to regulate valley polarization and demonstrate the promising application of magnetic heterojunctions in magneto-optoelectronics. [ABSTRACT FROM AUTHOR]