Afzal Khan

Single‐molecule magnets (SMMs) and low‐dimensional van der Waals (vdW) magnets are highly promising for quantum technologies, spintronics, and data storage, yet their integration into practical devices is frequently impeded by chemical reactivity, aggregation, or loss of magnetic function during processing. Encapsulation within carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) has emerged as a versatile strategy to protect, isolate, align, and electronically address these fragile magnetic species at the atomic scale. This review provides a comprehensive overview of encapsulated magnetic materials, focusing on two interconnected themes: molecular magnets and one‐dimensional (1D vdW magnetic heterostructures. We examine the fundamental principles governing nanotube encapsulation, contrasting the distinct host‐guest interactions in metallic/semiconducting CNTs versus insulating BNNTs. Foundational studies demonstrate that SMMs from Mn ₁₂ acetate and TbPc ₂ to endohedral metallofullerenes and organometallic DyCp ₃ retain their magnetic bistability upon encapsulation, with confinement sometimes enhancing relaxation times and suppressing quantum tunneling. Parallel advances have enabled the synthesis of truly 1D 1D vdW magnetic materials inaccessible by conventional means, including transition metal trihalide chains (CrX ₃ , VX ₃ ), dihalide chains (CrX ₂ ), and complex tellurides (V _x Te _y ), whose magnetic ground states such as ferromagnetic, antiferromagnetic, or spin glass are tunable through nanotube diameter and charge transfer. Spectroscopic signatures of host‐guest interactions, magnetic properties, and emerging applications in spintronics, quantum information, and biomedical imaging are critically assessed. We conclude by identifying key challenges such as synthetic control, scalability, and device integration that must be overcome to realize the technological potential of these remarkable magnetic heterostructures.

Nanotubes represent an important class of crystalline materials, but controlling their structures, particularly chiralities, remains a fundamental challenge. In this work, we report a strategy for synthesizing transition metal dichalcogenide nanotubes with preferred armchair chirality. Tin disulfide, molybdenum disulfide, and tungsten disulfide nanotubes were formed with high yield and structural purity inside boron nitride nanotube channels. Atomic-resolution imaging, electron diffraction, and circular dichroism revealed an armchair preference up to 83%. Density functional theory ruled out structural stability as the origin of this preference but confirmed that zigzag nanoribbons are energetically more stable. Machine learning potential molecular dynamics simulated that zigzag nanoribbons roll up to form armchair nanotubes, a process that was subsequently observed by in situ transmission electron microscope. This work may inspire the achievement of on-demand synthesis of various nanotubes with specific chiralities.

Due to the scarcity and high cost of precious metals, development of a noble metal-free, low-cost catalyst for hydrogen generation via water splitting is crucial. To develop an efficient HER catalyst, Ti, the ninth most abundant metal in Earth’s crust, was engineered systematically. The pristine transition metal titanium cannot drive an electrocatalytic hydrogen evolution reaction (HER) with an efficient rate in an acidic medium (0.5 M H₂SO₄). However, in situ growth of TiO₂ film on Ti surface achieves HER activity, showing an overpotential for 10 mAcm⁻² at 671.4 mV with a Tafel slope of 163.69 mV dec⁻¹. The electrocatalytic performance was further boosted by immobilizing CuO particles onto the as-developed TiO₂/Ti film, which shows 10 mA cm⁻² overpotential at 543.7 mV with a Tafel slope of 101.09 mV dec⁻¹. The CuO–TiO₂/Ti heterostructured electrode exhibited remarkable long-term stability, with the current density increasing by 36% over 25 h of continuous operation, suggesting gradual electrochemical activation while maintaining robust catalytic performance. In this research, detailed structural, surface, and electrochemical investigations, including SEM–EDX, EIS, OCP, and XPS analyses, verified the optimized formation of the TiO₂ layer and CuO incorporation, underscoring the positive impact of heterointerface engineering on HER enhancement.

A thiocyanate adlayer on a Au electrode suppresses H ₂ O ₂ decomposition and enables controlled active site generation for selective, stable and reproducible electrochemical sensing of H ₂ O ₂ via reduction reaction in alkaline medium.

Molybdenum disulfide (MoS₂) has gained attention for its promising gas-sensing capabilities due to its high surface area and tunable electronic properties. In this study, we investigate the time-dependent growth (under constant conditions) of sputtered MoS₂ films on ZnO nanorods and their impact on NO₂ sensing performance. ZnO nanorods, synthesized via a hydrothermal method, provide a high-surface-area template to enhance charge transport and gas adsorption. Gas-sensing experiments revealed a strong correlation between MoS₂ thickness and NO₂ response, with the 25-min-sputtered MoS₂ film exhibiting the highest response of 20.9%. The synergistic interaction between MoS₂ and ZnO nanorods facilitated charge transfer and enhanced adsorption sites for NO₂ molecules. These findings emphasize the critical role of time-dependent growth of MoS₂ film in modulating gas-sensing performance and provide insights into designing high-sensitivity NO₂ sensors at room temperature. This study contributes to the development of hybrid MoS₂/ZnO nanostructures for next-generation environmental monitoring applications.