Le Ngoc Long

Engineering phase coexistence and interfacial coupling in two-dimensional materials offers a powerful strategy for tailoring excitonic dynamics and light–matter interactions. Herein, we report hydrothermally synthesized mixed-phase (1T/2H)-MoS2/graphene nanohybrids and demonstrate how heterophase boundaries and graphene interfaces reconstruct the excitonic phase-space. X-ray diffraction, Raman spectroscopy, HRTEM and X-ray photoelectron spectroscopy collectively confirm the coexistence of metallic 1T-MoS2, semiconducting 2H-MoS2, and conductive graphene, while electron microscopy reveals few-layer MoS2 nanosheets intimately integrated with graphene scaffolds, generating abundant phase and interfacial junctions. Photoluminescence measurements exhibit pronounced spectral reconstruction characterized by red-shifted emission, linewidth broadening, intensity quenching, and the emergence of multiple emissive features within the 1.93–2.22 eV range. Spectral deconvolution reveals the coexistence of bright excitons, carrier-perturbed (Trion-like) states, interfacial emissive channels, and non-radiative relaxation pathways. These observations indicate that metallic 1T domains and graphene interfaces actively redistribute excitonic populations through charge transfer, dielectric screening, and interfacial electronic-state coupling. A unified excitonic phase-space model is proposed to describe the competition among intrinsic radiative recombination, interfacial exciton relaxation, carrier extraction, and dark-state population pathways. The results establish mixed-phase (1T/2H)-MoS2/graphene nanohybrids as a versatile platform for engineering excitonic photo-physics and tunable optical functionality in next-generation optoelectronic materials.

Supercapacitors and micro-supercapacitors are promising capacitive energy storage devices for portable electronics and microelectromechanical systems. However, their low volumetric energy and power density as compared to batteries might limit them from many practical applications. In this research, the low-dimension MoS2/graphene oxide nanocomposite (MoS2/C NC) was successfully synthesized by a simple hydrothermal approach and utilized it as an electrode material for supercapacitor applications. The obtained materials were systematically investigated by various characterization techniques. Field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) were used to evaluate surface morphology, microstructure and crystallite size; while the X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and Raman spectroscopy were used to analyze phase and chemical composition of the synthesized samples. The electrochemical capacitance properties were measured by cyclic voltammetry (CV) and electrochemical impedance spectroscope (EIS) techniques. From FE-SEM and HR-TEM results, it was evident that ultrathin two-dimensional (2D) MoS2 crystals were in-situ grown on the graphene oxide surface, resulting in rich porous three-dimensional (3D) architecture. The thickness and average lateral size of MoS2 crystals by HRTEM were around ~1.8–3.5 nm (~3–6 nm layers) and ~200–300 nm, respectively. The results of XRD, Raman, and XPS studies confirm that the as-grown MoS2 crystals have a predominantly hexagonal phase structure (2H-MoS2). Interestingly, thin film electrode prepared from the MoS2/C NC shows a high specific capacitance of ~118.5 F g−1 under 1 A g−1 with electrochemical active surface area of ~218.0 m2 g−1. The obtained high energy density of ~88.0 Wh kg−1 and a power density of ~367.0 W kg−1, along with low charge transfer resistance of the synthesized MoS2/C NC which make it a promising candidate for supercapacitor applications.

This work presents a comprehensive investigation into the phase engineering and interfacial reconstruction of 2D MoS ₂ /graphene nanocomposites synthesized via hydrothermal treatment at 170–250 °C. A key innovation lies in the controlled modulation of the 1T/2H‐MoS ₂ phase ratio, wherein low‐temperature synthesis enables stabilization of the highly conductive 1T phase, while elevated temperatures promote a transition to the semiconducting 2H phase. Simultaneously, defect‐laden graphene oxide is progressively restored to an sp ² ‐hybridized network, facilitated by MoS ₂ ‐mediated electron transfer and sulfur‐assisted reduction. Raman spectroscopy reveals a significant I _D / I _G ratio decline (from ≈1.28 to ≈0.07) and increased lateral crystallite size (≈15.0 to 260.6 nm), indicating enhanced graphitization. XPS and XRD investigation indicates a temperature‐induced 1T‐to‐2H MoS ₂ phase transition, with Mo 3 d (Mo 3 d _5/2 /Mo 3 d _3/2 ) peaks shifting from ≈228.4/231.7 eV (1T phase) to ≈229.1/232.3 eV (2H phase), along with deoxygenation and reduced surface functionalization. HRTEM visualizes the emergence of coherent 2H‐MoS ₂ nanodomains. Electrochemical analysis reveals a dramatic enhancement in conductivity (≈2.1 × 10 ⁻³ S m ⁻¹ ) and capacitance (≈567.6 F cm ⁻² ), driven by optimized phase composition and interfacial synergy. These findings underscore the pivotal role of synthesis temperature in tailoring mixed‐phase architectures and interfacial chemistry, offering a tunable platform for next‐generation optoelectronic devices, energy storage, catalysis, and membrane technologies.

In this research, ZnO/GO nanocomposites were successfully synthesized by a simple hydrothermal method using graphene oxide (GO) and zinc acetate dihydrate (Zn(CH₃COO)₂.2H₂O) as the reactants. The effect of the hydrothermal reaction time on the structure and optical property of the ZnO/GO was systematically investigated. The structure, morphology and chemical composition of the samples were measured by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and Raman and Fourier transform infrared (FTIR) spectroscopy, while the optical properties were measured using photoluminescence spectroscopy. The synthesized products consisted of large quantities of one-dimensional (1D) ZnO nanorods (NRs), which were dispersed uniformly on the GO surface. The XRD and Raman results reveal that the ZnO NRs in the fabricated samples had a hexagonal wurtzite structure with high crystalline quality. The FESEM and TEM images reveal that ZnO NRs with an average diameter in the range of ~85–270 nm and length in the range of ~0.3–6 μm were covered with GO sheets. Additionally, it was found that the crystallographic orientation of ZnO NRs was dependent not only on the hydrothermal reaction time but also on the presence of GO in the nanocomposites. However, the addition of GO did not affect the stoichiometric ratio and the crystal structure of ZnO NRs. The room-temperature PL results indicated that, compared to those of pure ZnO, the luminescence of the GO/ZnO nanocomposites was suppressed and shifted towards a higher wavelength (red shift), which was attributed to the incorporation of ZnO NRs within the GO matrix and the formation of a C-O-Zn chemical bond in the nanocomposites. The hydrothermal technique is considered one of the best routes due to its low cost, high growth rates, low-temperature synthesis, controllable crystallographic orientation, particle size, as well as morphology.

In this research, the magnetic Fe₃O₄/zeolite NaA nanocomposite (Fe₃O₄/ZA), Fe₃O₄ nanoparticles, and zeolite NaA have been synthesized by facile hydrothermal methods for adsorption removal of methylene blue from aqueous solution. The as-synthesized Fe₃O₄/ZA nanocomposite was characterized by X-ray diffraction (XRD), MicroRaman analysis, Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray fluorescence (XRF), N₂ adsorption isotherms (BET), and UV-VIS analysis. The results show that with a small weight loading of Fe₃O₄, the 3.3 Fe₃O₄/ZA sample exhibits a high adsorption capacity (40.36mg·g⁻¹) and removal efficiency (96.8) compared to that of the zeolite NaA (32.99mg·g⁻¹ and 79.11, respectively). Interestingly, the removal efficiency and the adsorption capacity increase rapidly with the increase of adsorption time (1060 minutes) and Fe₃O₄ loading (3.39.3 wt.) in the Fe₃O₄/ZA composition. The adsorption mechanism of MB molecules of the Fe₃O₄/ZA can be addressed at the combination of the interaction between active sites on the surfaces and edges of the invert spinel ferrite Fe₃O₄ nanoparticles and zeolite NaA with MB molecules. Our approach provides a simple, efficient, and scalable synthesis process that render practical applications of the magnetic Fe₃O₄/ZA nanocomposite as a lower-cost adsorbent for wastewater treatment.