Augmenting the double pipe heat exchanger efficiency using varied molar Ag ornamented graphene oxide (GO) nanoparticles aqueous hybrid nanofluids

The optimization of heat transfer in heat exchanging equipment is paramount for the efficient management of energy resources in both industrial and residential settings. In pursuit of this goal, this empirical study embarked on enhancing the heat transfer performance of a double pipe heat exchanger (DPHX) by introducing silver (Ag)-graphene oxide (GO) hybrid nanofluids into the annulus of the heat exchanger. To achieve this, three distinct molar concentrations of Ag ornamented GO hybrid nanoparticles were synthesized by blending GO nanoparticles with silver nitrate at molarities of 0.03 M, 0.06 M, and 0.09 M. These Ag-GO hybrid nanoparticles were then dispersed in the base fluid, resulting in the formation of three distinct hybrid nanofluids, each with a consistent weight percentage of 0.05 wt%. Thorough characterization and evaluation of thermophysical properties were performed on the resulting hybrid nanomaterials and nanofluids, respectively. Remarkably, the most significant enhancement in heat transfer coefficient, Nusselt number, and thermal performance index (62.9%, 33.55%, and 1.29, respectively) was observed with the 0.09 M Ag-GO hybrid nanofluid, operating at a Reynolds number of 1,451 and a flow rate of 47 g/s. These findings highlight the substantial improvement in thermophysical properties of the base fluid and the intensification of heat transfer in the DPHX with increasing Ag molarity over GO. In summary, this study emphasizes the vital importance of optimizing the molarity of the material, which also plays a significant role in nanoparticle synthesis to achieve the optimal amplification of heat transfer

Supramolecular Complexation of \u3cem\u3eN\u3c/em\u3e-Alkyl- and \u3cem\u3eN\u3c/em\u3e,\u3cem\u3eN\u3c/em\u3e′-Dialkylpiperazines with Cucurbit[6]uril in Aqueous Solution and in the Solid State

Water seeds: Complex stoichiometry/composition and degree of oligomerization (oligomeric supramolecular complex formation) of cucurbit[6]uril (CB[6]) with N-alkyl- and N,N′-dialkylpiperazine were investigated in aqueous solutions by means of isothermal titration calorimetry (ITC), ESI-MS, NMR and light scattering measurements. Complex stoichiometry/composition and degree of oligomerization (oligomeric supramolecular complex formation) of cucurbit[6]uril (CB[6]) with N-alkyl- and N,N′-dialkylpiperazine were investigated in aqueous solutions by means of isothermal titration calorimetry (ITC), ESI-MS, NMR and light scattering measurements. It was found that the complex stability and the degree of oligomerization increase with elongating the alkyl chain attached to the piperazine core. X-ray crystallographic studies revealed a clear correlation between the structure of CB[6]–alkylpiperazine crystals obtained from aqueous solutions and the molecular weight/properties of host–guest oligomers existed in the solution as supramolecular “seeds” of crystal formation

Supramolecular Velcro for Reversible Underwater Adhesion

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Reversible morphological transformation between polymer nanocapsules and thin films through dynamic covalent self-assembly

A facile method has been developed for synthesizing polymer nanocapsules and thin films using multiple in-plane stitching of monomers by the formation of reversible disulfide linkages. Owing to the reversibility of the disulfide linkages, the nanostructured materials readily transform their structures in response to environmental changes at room temperature. For example, in reducing environments, the polymer nanocapsules release loaded cargo molecules. Moreover, reversible morphological transformations between these structures can be achieved by simple solvent exchanges. This work is a novel approach for the formation of robust nano/microstructured materials that dynamically respond to environmental stimuli.113141sciescopu

Guest Binding Dynamics with Cucurbit[7]uril in the Presence of Cations

The binding dynamics of <i>R</i>-(+)-2-naphthyl-1-ethylammonium cation (NpH⁺) with cucurbit[7]uril (CB[7]) was investigated. Competitive binding with Na⁺ or H₃O⁺ cations enabled the reaction to be slowed down sufficiently for the kinetics to be studied by fluorescence stopped-flow experiments. The binding of two Na⁺ cations to CB[7], i.e., CB[7]·Na⁺ (<i>K</i>₀₁ = 130 ± 10 M^–1) and Na⁺·CB[7]·Na⁺ (<i>K</i>₀₂ = 21 ± 2 M^–1), was derived from the analysis of binding isotherms and the kinetic studies. NpH⁺ binds only to free CB[7] ((1.06 ± 0.05) × 10⁷ M^–1), and the association rate constant of (6.3 ± 0.3) × 10⁸ M^–1 s^–1 is 1 order of magnitude lower than that for a diffusion-controlled process and much higher than the association rate constant previously determined for other CB[<i>n</i>] systems. The high equilibrium constant for the NpH⁺@CB[7] complex is a consequence of the slow dissociation rate constant of 55 s^–1. The kinetics results showed that formation of a complex between a positively charged guest with CB[<i>n</i>] can occur at a rate close to the diffusion-controlled limit with no detection of a stable exclusion complex