Nilay Krishna Mukhopadhyay

Dopamine levels are linked to neurological illnesses like Parkinson's and Alzheimer's. Thus, reliable and sensitive detection of dopamine is crucial for early diagnosis and surveillance of neurodegenerative diseases. Non‐noble‐metal‐based nanomaterials are ideal for light‐mediated sensing of organic molecules. Among these, two‐dimensional (2D) quasicrystal (QC) structures consisting of five elements ( Al ₇₀ Co ₁₀ Fe ₅ Ni ₁₀ Cu ₅ (2D Al QC)) provide active sites due to their high surface‐to‐volume ratio, making them excellent for organic chemical sensing. Here, we propose a simple, label‐free, spatial self‐phase‐modulation (SSPM)‐based sensing method in liquid form. SSPM‐based time evolution of the diffraction pattern for varied mixing levels of a 1100 ppb dopamine solution shows a shift in the SPR‐activated 2D Al QC nanostructure solution. The 1100 ppb solution shows a different dN / dI value, indicating a change in sensitivity to the nonlinear refractive index and time constant. SSPM is used to demonstrate dopamine‐sensing methods and to perform qualitative and quantitative evaluations. The SSPM‐based sensing has been further compared with other optical sensing methods, such as Raman Spectroscopy, UV‐vis Spectroscopy, and FTIR Spectroscopy. The experimental observations are also explained using DFTB‐based simulations.The current SSPM method can be used for rapid, large‐scale medical diagnostics.

The Fe-enriched high entropy alloy (HEA) shows the formation of BCC (a = 0.287 nm) and χ-phase (a = 0.889 nm) after mechanical alloying (MA) at 40 h. After spark plasma sintering (SPS) at 900 °C and 50 MPa, the dual-phase structure of FCC and BCC phases along with the χ-phase was observed. The average microhardness and elastic modulus of the SPSed sample were obtained as 5.6 ± 0.2 GPa and 131 ± 5 GPa respectively. The compressive yield strength of the SPSed sample was 1550 ± 100 MPa with ductility of ~ 11%. The dominant strengthening mechanisms are dislocation and grain boundary strengthening, which can account for ~ 65% of the observed flow stress. The correlation between the phases formed and thermal stability was correlated with different thermodynamic parameters and phase prediction by ThermoCalc software. Graphical abstract

Attempts are made to synthesize Al₅Fe₂ aluminide‐based composites by mechanical alloying (MA) and cryomilling (CM). The XRD and TEM results of the milled samples confirm the formation of a major B2‐AlFe phase (0.2887 ± 0.0003 nm; cP2) along with the minor amount of Al₅Fe₂ phase. Nanocrystalline grains of ≈16 nm and an average particle size of 4.0 ± 0.36 μm are evident. A significant refinement in the crystallite size (≈10 nm) and average particle size (1.0 ± 0.03 μm) is achieved after 10 h CM of 60 h MAed powder. CM enhances the phase fraction of the Al₅Fe₂ phase. The DSC thermogram discerns three exothermic heating events due to phase transformation. These can be corroborated by the structural transformation of the B2‐AlFe phase to the orthorhombic Al₅Fe₂ phase. The phase obtained as a result of 60 h of MA transforms to orthorhombic Al₅Fe₂ along with a minor amount of pre‐existing B2‐AlFe structure after annealing at 600 °C. It becomes more stable after annealing at 900 °C. Further, the 60 h milled sample displays soft ferromagnetic properties. The saturation magnetization decreases on CM and annealing due to phase transition from B2‐AlFe to Al₅Fe₂ phase. Coercivity is reduced when the MA sample is annealed due to an increase in crystallite size and a reduction in lattice strain.

Efforts are made to understand the influence of milling intensity on structure, morphology, magnetic and thermoelectric properties of nonequiatomic nanostructured AlSiCrMnFeNiCu high‐entropy alloy (HEA) powders prepared by cryomilling. These powders are cryomilled with different ball‐to‐powder ratios (BPR) and present a dual‐phase structure containing a major B2‐type and a minor Cr ₅ Si ₃ ‐type phase. An increase in BPR enhances the refinement of crystallite size, grain size, and particle size accompanied by a decrease in the phase fraction of the minor Cr ₅ Si ₃ ‐type phase. Magnetic measurements revealed that at room temperature, sufficient increase in BPR leads to a transition from multi‐domain behavior to single‐domain behavior which leads to enhancement in soft magnetic properties. Thermal measurements show the presence of different magnetic phase transitions which vary with an increase in BPR. A change of charge carrier type from p to n‐type was observed as the grain size is reduced. The figure of merit decreases with the decrease in grain size from 2 × 10 ^–5 for as‐cast powders and is lowest for the smallest grain‐sized sample due to a decrease in electrical conductivity. This study shows the possibility of exploring nonequiatomic low‐density HEAs whose functional properties can be tailored, offering flexibility in material design for specific applications.