Considering the huge consumption of fossil fuels and cumulative energy demands in the high-tech society, energy storage devices, particularly supercapacitors, play a pivotal role in exploring alternative sources of renewable energy. To focus on potential supercapacitor electrode materials, they should possess essential features such as a massive surface area, good conductivity, and a plentiful number of active sites. Therefore, the integration of a large surface area of two-dimensional (2D) materials with high conductivity with carbon quantum dots (CQDs) containing a large number of active sites is an elegant approach for achieving excellent electrode materials for supercapacitor applications. In the present work, we decorate highly conducting 2D Ti₃C₂T_x MXene sheets with nitrogen (N) and sulfur (S) co-doped CQDs (NS-CQDs) as a source of numerous active sites to explore their potential as electrode materials for supercapacitor applications. We synthesize three samples exhibiting impressive specific capacitances (C_sp) of 562.7 F g⁻¹, 725.7 F g⁻¹, and 523.4 F g⁻¹, respectively, at a current density of 1 A g⁻¹ with excellent cycling stabilities of 95.5%, 98.3%, and 94.1%, respectively, at a current density of 10 A g⁻¹ over 10 000 cycles. The origin of this excellent C_sp is the electron clouds near the N- and S-doped atoms which act as active sites. Finally, these unique hybrid composite materials with high C_sp, high energy density (170.34 W h kg⁻¹ at a power density of 1290.98 W kg⁻¹), and outstanding electrochemical stability show significant promise in the field of storage device applications.

To study the 2D materials, an interface interaction is very important to tune the physical properties because of the large specific surface area. When the antiferromagnetic α-Fe₂O₃ is grown in a single-crystalline form on a diamagnetic MoS₂, enormous changes in magnetic properties are observed in the 2D composite system. Strong ferromagnetism with a giant coercivity of 1.8 T is observed in this single-crystalline α-Fe₂O₃/MoS₂ heterostructure. It is noted that thinner sheets show better coercivity than the thicker sheets, and the coercivity decreases with the increase in temperature. This huge coercivity in larger and thinner single-crystalline α-Fe₂O₃ sheets grown on a MoS₂ arises due to charge transfer from “S” to “Fe” and the surface pinning effect at the interface. A large negative magnetoresistance with a maximum value of 15% is achieved due to the spin-spin interaction, and a positive magnetoresistance is also observed at low field and high temperature as a result of the spin splitting effect.

Because of the potential application of $\mathrm{Co}{\left(\mathrm{OH}\right)}_2$ in a magnetic cooling system as a result of its superior magnetocaloric effect many people have investigated magnetic properties of $\mathrm{Co}{\left(\mathrm{OH}\right)}_2$. Unfortunately, most of the works have been carried out on the $\beta \text{−}\mathrm{Co}{\left(\mathrm{OH}\right)}_2$ phase due to the fact that the $\alpha \text{−}\mathrm{Co}{\left(\mathrm{OH}\right)}_2$ phase is very unstable and continuously transformed into the stable $\beta \text{−}\mathrm{Co}{\left(\mathrm{OH}\right)}_2$ phase. However, in the present work, using a $\mathrm{Mo}{\mathrm{S}}_2$ sheet as a two-dimensional template, we have been able to synthesize a stable $\alpha \text{−}\mathrm{Co}{\left(\mathrm{OH}\right)}_2$ phase in addition to a $\beta \text{−}\mathrm{Co}{\left(\mathrm{OH}\right)}_2$ phase by varying the layer thickness. It is seen that for thinner samples the $\beta$ phase, while for thicker samples $\alpha$ phase, is grown on the $\mathrm{Mo}{\mathrm{S}}_2$ surface. Magnetic measurements are carried out for the samples over the temperature range from 2 to 300 K and it is seen that for the $\beta$ phase, ferromagnetic ordering with fairly large coercivity (1271 Oe) at 2 K is obtained instead of the usual antiferromagnetism. The most interesting result is the observation of ferromagnetic ordering with a transition temperature (Curie temperature) more than 100 K in the $\alpha \text{−}\mathrm{Co}{\left(\mathrm{OH}\right)}_2$ phase. Complete saturation in the hysteresis curve under application of very low field having coercivity of $\sim 162\mathrm{Oe}$ at 2 K and 60 Oe at 50 K is obtained. A thin stable $\alpha \text{−}\mathrm{Co}{\left(\mathrm{OH}\right)}_2$ phase grown on $\mathrm{Mo}{\mathrm{S}}_2$ surface with very soft ferromagnetic ordering will be very useful as the core material in electromagnets.