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Creators/Authors contains: "Paniagua-Guerra, Luis E"

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  1. This paper reports on the effects of shear rate and interface modeling parameters on the hydrodynamic slip length (LS) for water–graphite interfaces calculated using non-equilibrium molecular dynamics. Five distinct non-bonded solid–liquid interaction parameters were considered to assess their impact on LS. The interfacial force field derivations included sophisticated electronic structure calculation-informed and empirically determined parameters. All interface models exhibited a similar and bimodal LS response when varying the applied shear rate. LS in the low shear rate regime (LSR) is in good agreement with previous calculations obtained through equilibrium molecular dynamics. As the shear rate increases, LS sharply increases and asymptotes to a constant value in the high shear regime (HSR). It is noteworthy that LS in both the LSR and HSR can be characterized by the density depletion length, whereas solid–liquid adhesion metrics failed to do so. For all interface models, LHSR calculations were, on average, ∼28% greater than LLSR, and this slip jump was confirmed using the SPC/E and TIP4P/2005 water models. To address the LS transition from the LSR to the HSR, the viscosity of water and the interfacial friction coefficient were investigated. It was observed that in the LSR, the viscosity and friction coefficient decreased at a similar rate, while in the LSR-to-HSR transition, the friction coefficient decreased at a faster rate than the shear viscosity until they reached a new equilibrium, hence explaining the LS-bimodal behavior. This study provides valuable insights into the interplay between interface modeling parameters, shear rate, and rheological properties in understanding hydrodynamic slip behavior. 
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  2. Turning gold nanoparticles (AuNPs) into nanoscale heat sources via light irradiation has prompted significant research interest, particularly for biomedical applications, over the past few decades. The AuNP’s tunable photothermal effect, notable biocompatibility, and ability to serve as vehicles for temperature-sensitive chemical linkers enable thermo-therapeutics, such as localized drug/gene delivery and thermal ablation of cancerous tissue. Thermal transport in aqueous AuNP solutions stands as the fundamental challenge to developing targeted thermal therapies; thus, this review article surveys recent advancements in our understanding of heat transfer and surface chemistry in AuNPs, with a particular focus on thermal boundary conductance across gold- and functionalized-gold-water interfaces. This review article highlights computational advances based on molecular dynamics simulations that offer valuable insights into nanoscopic interfacial heat transfer in solvated interfaces, particularly for chemically functionalized AuNPs. Additionally, it outlines current experimental techniques for measuring interfacial thermal transport, their limitations, and potential pathways to improve sensitivity. This review further examines computational methodologies to guide the accurate modeling of solvated gold interfaces. Finally, it concludes with a discussion of future research directions aimed at deepening our understanding of interfacial heat transfer in solvated AuNPs, crucial to optimize thermoplasmonic applications. 
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    Free, publicly-accessible full text available September 18, 2026