The iron selenide (Fe–Se) family of nanoparticles (Fe x Se y where x/y ranges from 1:2 to 1:1) has been fabricated by a thermal decomposition method. The control over solution chemistry has been developed by intensively investigating the effect of reaction parameters by means of wide-angle X-ray scattering, leading to the rich insights into the phase-evolution mechanism of the Fe–Se system. The phase transformation followed the FeSe2 → Fe3Se4 → Fe7Se8 → FeSe sequence in the temperature range of 110–300 °C. The deep mechanistic insight helped in the identification of optimized conditions needed to crystallize the individual phase of the Fe–Se system as well as control of the morphology, crystalline phase purity, and thermal stability of the obtained Fe–Se nanoparticles.

Crystalline iron selenide (Fe 3 Se 4 ) nanoparticles (NPs) present a useful model system for a fundamental understanding of magnetism apart from having potential applications in permanent-magnet-related technologies. Despite significant advancements in understanding of the nucleation and growth processes, control over size and shape tunability is nontrivial, especially for the transition metal chalcogenides (TMC). The Wulff theorem states that if a crystal can grow purely under thermodynamic control of parameters then it will adopt the shape determined by the surface-energy minimization, i.e., the surface energy minimization will drive the growth of each crystalline facet. However, the known or unknown, controllable or uncontrollable parameters of a typical reaction which makes kinetic growth more art than science, depending upon whether we understand them or not. There is hardly any study based on existing models and theories to explain the TMC morphology evolution. In this work, there is a conscious effort to know, understand, and control the individual role of various reaction pathways on the shape and size of the Fe 3 Se 4 nanocrystals. A qualitative growth mechanism is proposed based on the diffusion and reaction processes. Furthermore, the influence of shape/size on the magnetic parameters such as coercivity (H C ), magnetization (M 60kOe ), effective magnetic anisotropy constant (K eff ), energy product (BH max ), and average blocking temperature (T B ) is investigated for Fe 3 Se 4 NPs. After diving deeper into the science of crystal growth, our insight provides valuable guidance on experimental conditions for the synthesis of Fe 3 Se 4 NPs with tunable sizes/shapes which for the first time can be extended to most TMCs.

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This article describes the synthesis of ethyleneglycol (E) phosphoramidite and its incorporation into the thrombin binding aptamer (TBA) sequence at loop positions. Circular dichroism (CD) study revealed no major disturbances in the secondary structure of TBA by the abasic E unit and the derived oligomers exhibited a typical antiparallel chair‐like conformation similar to that of TBA. UV and CD spectroscopy, together with anti‐coagulation and HPLC studies revealed that although nuclease stability was enhanced, and anti‐coagulation reasonably good, the thermal stability of the quadruplexes was adversely affected.