Browsing by Author "Tootoonchian, Pedram"

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Open Access
A dormant reagent reaction-diffusion method for the generation of Co-Fe Prussian Blue analogue periodic precipitate particle libraries
(Wiley-VCH GmbH, 2023-08-25) Tootoonchian, Pedram; Kwiczak-Yiğitbaşı, Joanna; Turab Ali Khan, Muhammad; Chalil Oglou, Ramadan; Holló, G.; Karadaş, Ferdi; Lagzi, I.; Baytekin, Bilge
Liesegang patterns that develop as a result of reaction-diffusion can simultaneously form products with slightly different sizes spatially separated in a single medium. We show here a reaction-diffusion method using a dormant reagent (citrate) for developing Liesegang patterns of cobalt hexacyanoferrate Prussian Blue analog (PBA) particle libraries. This method slows the precipitation reaction and produces different-sized particles in a gel medium at different locations. The gel-embedded particles are still catalytically active. Finally, the applicability of the new method to other PBAs and 2D systems is presented. The method proves promising for obtaining similar inorganic framework libraries with catalytic abilities. © 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.
Open Access
Anisotropic actuation in salty agarose gel actuators
(Springer, 2023-08-01) Tootoonchian, Pedram; Bahçeci, Levent; Baytekin, Bilge
When hydrogels that can reversibly dehydrate/rehydrate are physically combined with a constant water supply, the cycles can be controlled by on/off states and the positions of an external light source. The shrinking upon dehydration upon illumination causes bending towards the light source, and rehydration in the light-off state restores the initial shape. This simple material feedback mechanism mimics the self-regulating heliotropism (sun tracking) and nyctinasty (leaf opening) movements of plants. In this work, we show the effect of some common salts on the bending behavior of actuators entirely made of hydrogel. The ‘salty’ actuators exhibit different motion kinetics regarding the unique chemical characteristics of each ion. We display that this chemistry of ions also enables us to program the kinetics in a single actuator using the differences in evaporation/diffusion rate of water in the salty gels. This programmability of the motion in a hydrogel actuator with the inclusion of salts can be used to achieve complex behavior observed in living organisms straightforwardly.
Open Access
Chemical tracking of temperature by concurrent periodic precipitation pattern formation in polyacrylamide gels
(American Chemical Society, 2022-01-20) Khan, Muhammad Turab Ali; Kwiczak-Yiğitbaşı, Joanna; Tootoonchian, Pedram; Morsali, Mohammad; Lagzi, Istvan; Baytekin, Bilge
In nature, nonequilibrium systems reflect environmental changes, and these changes are often “recorded” in their solid body as they develop. Periodic precipitation patterns, aka Liesegang patterns (LPs), are visual sums of complex events in nonequilibrium reaction–diffusion processes. Here we aim to achieve an artificial system that “records” the temperature changes in the environment with the concurrent LP formation. We first illustrate the differences in 1-D LPs developing at different temperatures in terms of band spacings, which can demonstrate the time, ramp steepness, and extent of a temperature change. These results are discussed and augmented by a mathematical model. Using scanning electron microscopy, we show that the average size of the CuCrO4 precipitate also reflects the temperature changes. Finally, we show that these changes can also be “recorded” in the 2-D and 3-D LPs, which can have applications in long-term temperature tracking and complex soft material design.
Open Access
The formation of Liesegang patterns of cobalt hexacyanoferaate Prussian blue analogue in polyacrylamide gels
(2022-01) Tootoonchian, Pedram
The formation of patterns in nature has always fascinated scientists who try to understand the mechanism behind this complex phenomenon. Liesegang patterns (LPs) are one category of periodic precipitations patterns formed by the reaction- diffusion (RD) system, studied and modeled by chemists and mathematicians for over a century. The majority of the focus has been on understanding the formation of these patterns, modeling them, and studying the effect of different gel types, gel concentrations, and inner and outer concentrations on various systems. There are only a few examples in the literature showing the effect of temperature, electric or magnetic field, and mechanical force on LPs and controlling the pattern formation by these external stimuli, and more importantly, showing a possible application of these systems. In this work, we show a novel approach to form LPs in a hydrogel medium, track the band formation with temperature, characterize each band, and last but not least, suggest a useful application for these LPs. This study mainly concentrates on the pattern formation of cobalt Prussian blue, but LPs of some other Prussian Blue Analogues (PBAs) are also shown. First, we propose a new method to form PBAs LPs formation. Then, we track the band formation by changing the system's temperature. To understand the effect of temperature on the microscale, we characterize each band using SEM, EDX, and XPS to analyze particles size and Co/Fe ratio. Finally, we use each band as electrocatalysts for water oxidation reactions in water splitting.
Open Access
Lyotropic “salty” tuning for straightforward diversification and anisotropy in hydrogel actuators
(American Chemical Society, 2025-01-01) Tootoonchian, Pedram; Bahçeci, Levent; Budnyk, Andriy; Okur, Halil İbrahim; Baytekin, Bilge
The specific ion effect (SIE), the control of polymer solubility in aqueous solutions by the added ions, has been a phenomenon known for more than a century. The seemingly simple nature of the ion–polymer–water interactions can lead to complex behaviors, which have also been exploited in many applications in biochemistry, electrochemistry, and energy harvesting. Here, we show an emerging diversification of actuation behaviors in “salty” hydrogel and hydrogel-paper actuators. SIE controls not only the dehydration speeds but also the water diffusion and mechanical properties of the gels, leading to composite actuation behavior. Most reported thermally activated hydrogel actuators suffer from expensive precursors or complex fabrication processes. This work addresses these issues by using a physicochemical effect displayed within an inexpensive gel with common salts. SIE-controlled anisotropic actuation in geometrically different systems provides a demonstration of how such physicochemical effects can lead to higher complexity in basic soft material design and hydrogel soft robotics.
Open Access
Periodic stratification of colloids in a liquid phase produced by a precipitation reaction and gel swelling
(American Chemical Society, 2024-05-17) Tootoonchian, Pedram; Holló, Gábor ; Uzunlar, Rana; Lagzi, Istvan; Baytekin, Bilge
Pattern formation is a frequent phenomenon occurring in animate and inanimate systems. The interplay between the mass transport of the chemical species and the underlying chemical reaction networks generates most patterns in chemical systems. Periodic precipitation is an emblematic example of reaction–diffusion patterns, in which the process generates a spatial periodic structure in porous media. Here, we use the dormant reagent method to produce colloidal particles of Prussian blue (PB) and PB analogues at the liquid–gel interface. The generated particles produced a stable periodic stratification pattern in time in the liquid phase placed on top of the solid hydrogel. The phenomenon is governed by periodic swelling of the gel driven by the osmotic stress and stability of the formed particles. To illustrate the phenomenon, we developed an extended reaction–diffusion model, which incorporated the gel swelling and sedimentation effect of the formed colloids and could qualitatively reproduce the pattern formation in the liquid phase.