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Two self-healing-type supramolecular Ni(II)-metallogels are achieved. The choice of proper low-molecular-weight organic gelators such as trans-butenedioic acid (i.e., trans-BDA) and cis-butenedioic acid (i.e., cis-BDA) and triethylamine in N,N'-dimethylformamide solvent facilitates the metallogelation process. Through rheological investigations the mechanical robustness and viscoelastic properties of synthesized metallogels are explored. An in-depth exploration of thixotropic behavior also supports their self-healing features. Notably, distinct variations in morphologies of metallogels are also ascertained through field emission scanning electron microscopy studies. Furthermore, the existence of versatile noncovalent supramolecular interactions operating throughout the metallogel network is clearly revealed via Fourier transform infrared spectroscopy. Electrospray ionization-mass studies also explore the construction protocol of individual Ni(II)-metallogels. The Z-scan measurements with a 532 nm continuous wave laser were employed to unveil the nonlinear thermo-optical response of two synthesized self-healing metallogels, i.e., trans-BDA-TEA@Ni(II) and cis-BDA-TEA@Ni(II). Crucial parameters like the nonlinear refractive index, nonlinear absorption coefficient, thermo-optical coefficient, and third-order susceptibility of these metallogels are obtained. Metallogels show negative signs for the nonlinear refractive index and the nonlinear absorption coefficient. The real parts of the third-order susceptibility for these metallogels are much greater than the imaginary parts (i.e., χR(3) > χI(3)), making such metallogels very promising for all optical-switching applications.

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Indolamines (e.g., serotonin and melatonin) are tryptophan-derived class of neurotransmitters and neuromodulators that play crucial roles in mood regulation, sleep-wake cycles, and gastrointestinal functions. These biogenic amines exert their effects by binding to specific receptors in the central nervous system, influencing neuronal activity and signalling cascades. Indolamines are vital in maintaining homeostasis, and imbalances in their levels have been implicated in various neurological and psychiatric disorders. Hence, in the present study, we have investigated the nonlinear properties of indolamines under a continuous wave (CW) and pulsed laser excitation using the closed-aperture (CA) Z-scan technique. The CA Z-scan is a cost-effective and sensitive analytical tool for investigating nonlinear properties. It is observed that indolamines show negative refractive and positive absorptive nonlinearity under in vitro physiological conditions. The origin of nonlinearity is ascribed to the thermo-optical effect governed by the saturated atomic absorption and molecular orientation mechanisms under CW and pulsed laser excitation, respectively. The strength of nonlinearity is found to vary linearly with the concentration of indolamines. Overall, serotonin possesses stronger nonlinearity than melatonin. The maximum nonlinearity (refractive index (n2) & absorption coefficient (ß)) for melatonin under CW and pulsed laser excitations are (-1.266 × 10-12 m2W-1 and -1.883 × 10-17 m2W-1) & (8.046 × 10-8 mW-1 and 1.516 × 10-13 mW-1), respectively. Meanwhile, the maximum n2 and ß under pulsed laser excitation for serotonin are obtained as -3.195 × 10-17 m2W-1 and 6.149 × 10-12 mW-1, respectively. The outcome of the results may be utilized in understanding processes mediated by indolamines and designing therapeutic interventions.

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Hematin anhydride (ß-hematin), the synthetic analogue of the malaria pigment, "hemozoin", is a heme dimer produced by reciprocal covalent bonds among carboxylic acid groups on the protoporphyrin-IX ring and the iron atom present in the two adjacent heme molecules. Hemozoin is a disposal product formed from the digestion of hemoglobin present in the red blood cells infected with hematophagous malaria parasites. Besides, as the parasites invade red blood cells, hemozoin crystals are eventually released into the bloodstream, where they accumulate over time in tissues. Severe malaria infection leads to significant dysfunction in vital organs such as the liver, spleen, and brain in part due to the autoimmune response to the excessive accumulation of hemozoin in these tissues. Also, the amount of these crystals in the vasculature correlates with disease progression. Thus, hemozoin is a unique indicator of infection used as a malaria biomarker and hence, used as a target for the development of antimalarial drugs. Hence, exploring various properties of hemozoin is extremely useful in the direction of diagnosis and cure. The present study focuses on finding one of the unknown properties of ß-hematin in physiological conditions by using the Z-scan technique, which is simple, sensitive, and economical. It is observed that hemozoin possesses one of the unique material properties, i.e., nonlinearity with a detection limit of âˆ¼ 15 µM. The self-defocusing action causes ß-hematin to exhibit negative refractive nonlinearity. The observed data is analyzed with a thermal lensing model. We strongly believe that our simple and reliable approach to probing the nonlinearity of ß-hematin will provide fresh opportunities for malaria diagnostics & cure in the near future.

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The generation of solvent-directed self-healing supramolecular Ni(II) metallogels of glutaric acid (i.e., Ni-Glu-DMF and Ni-Glu-DMSO) is described in this article. Polar aprotic solvents like N,N'-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) are separately entrapped into the Ni(II)-acetate salt and glutaric acid-mediated networks to attain the semisolid flexible scaffolds. The gel nature of the fabricated materials is experimentally proven through different rheological tests such as amplitude sweep, frequency sweep, and thixotropic (time sweep) measurements. The self-repairing strategy and load-bearing features of the synthesized metallogel are studied in this work. The different supramolecular noncovalent interactions working within the soft scaffold are clearly explored. The formation strategy and the microstructural features of these synthesized metallogels are scrutinized through a Fourier transform infrared (FT-IR) spectroscopy study and field-emission scanning electron microscopy (FESEM) morphological analyses. The FT-IR spectroscopy observation displays a considerable amount of shifting of the infrared (IR) peaks of the xerogel samples of both the metallogels Ni-Glu-DMF and Ni-Glu-DMSO. The electrospray ionization (ESI)-mass spectroscopy result demonstrates the plausible construction of the metallogel network. In order to examine the nonlinear optical characteristics of the two synthesized self-healing metallogels Ni-Glu-DMSO and Ni-Glu-DMF, Z-scan measurements are carried out with a continuous wave (CW) diode-pumped solid-state (DPSS) laser at 532 nm. The nonlinear refractive index, nonlinear absorption coefficient, thermo-optical coefficient, and third-order susceptibility of these metallogels were evaluated by analyzing the experimental data from the Sheik-Bahae formalism. The nonlinear thermo-optical study reveals that these solvent-dependent metallogels show negative signs of nonlinear refractive index and nonlinear absorption coefficient. The figure of merit calculated for these compounds shows good agreement for their use in nonlinear photonic devices.

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Dopamine (DA) is a widely researched catecholamine best known for its role in motor, motivation, addiction, and reward. Disruption in dopamine homeostasis and signaling within the central nervous system (CNS) can lead to disorders such as attention deficit hyperactivity disorder (ADHD), schizophrenia, Parkinson's disease, and obsessive-compulsive disorder. In the periphery, circulating DA is stored in blood platelets, and its disruption correlates with pathological conditions such as head and neck paragangliomas, Huntington's chorea, and schizophrenia. Various methods to sensitively and selectively detect dopamine have been reported, but sparse attempts have been made to exploit its intrinsic properties. Previously, we have harnessed dopamine's natural mid-ultraviolet auto-fluorescence to carry out its label-free imaging in live brain tissues. Recently, we used the closed-aperture (CA) Z-scan method to provide the first line of evidence on the existence of dopamine nonlinearity. Here, we utilized this simple, sensitive, and straightforward CA Z-scan technique and coupled this with theoretical simulations to further investigate the nonlinear photophysical properties of DA under physiological conditions. Our combined approach revealed that the nonlinear property of dopamine is governed by the thermo-optical effects, and the CA Z-scan profiles can be modulated by parameters such as phase-shift, orders of absorption, and time dependency. Simple and physiologically relevant systems, such as the platelets, are amenable to Z-scan analysis, thereby empowering us to scrutinize in the future if nonlinearity and its alterations, if any, have a direct bearing on DA homeostasis and associated diseases.

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Norepinephrine (NE), a crucial modulatory neurotransmitter, plays a significant role in human physiology. Here, we use the Z-scan technique to investigate the nonlinear properties of NE at physiological conditions. Results reveal that NE exhibits thermo-optical nonlinearity. Outcomes can be utilized to investigate noradrenergic processes in correlation with various diseases.

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