Mandler's group deals with a wide range of scientific activities spanning from basic to applied research. The common base of these activities is electrochemistry, surface science and coatings. During the last years, we have specifically focused on the following research activities:

Nanoparticle-Imprinted Matrix (NAIM)

This is a field, which was initiated by us a few years ago and is an interesting expansion of the well-established molecularly imprinted polymer (MIP) approach. We have shown that nanovoids can be formed by adsorbing nanoparticles on solid electrodes followed by filling the non-occupied areas in between the nanoparticles with a matrix formed usually by electropolymerization. Then, the nanoparticles are removed and the nanovoids can be used to reuptake the originally imprinted nanoparticles. We have demonstrated that to achieve a high reuptake efficiency there must be not only a physical matching of the size and structure between the nanovoid and the nanoparticle but also a chemical matching of their surface functionalities. This project which is currently supported by the Israel Science Foundation has already resulted in very nice papers and interesting findings^1-3. For example, we have shown that NAIM systems imprinted with nanoparticles stabilized by different isomers are highly selective towards the initially imprinted nanoparticles. Furthermore, a NAIM system for the selective recognition of nanoparticles in the gaseous phase has also been designed. This is a field that we have only touched its tip and we are currently exploring more and more exciting aspects and applications.

 

(1)        Savchenko, P.; Zelikovich, D.; Sinai, H. E.; Baer, R.; Mandler, D. The Effect of the Capping Agents of Nanoparticles on Their Redox Potential. J. Am. Chem. Soc. 2024, 146, 22208-22219.

(2)        Zelikovich, D.; Savchenko, P.; Mandler, D. High Recognition of Isomer-Stabilized Gold Nanoparticles through Matrix Imprinting. ACS Appl. Mater. Interfaces 2023, 15, 32687-32696.

(3)        Zelikovich, D.; Dery, L.; Sagi-Cohen, H.; Mandler, D. Imprinting of nanoparticles in thin films: Quo Vadis? Chem. Sci. 2023, 14, 22.

 

 

Silica nanoparticles of different sizes accommodate nanocavities imprinted by 100 nm nanoparticles.

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Energy storage (supercapacitors, batteries and hydrogen)

This is a topic, which we entered a few years ago. Initially, we focused on the development of hybrid supercapacitors, aiming to bridge between batteries and supercapacitors. We have slowly paved our way where the approach has been to combine 2D capacitive and faradaic materials in one electrode. We have used the “nano to nano” approach⁴ and collaborated with the group of Prof. Hao at Nanjing University of Science^5,6 and Technology as well as with Prof. Xu Zhichuan from Nanyang Technological University. The electrodes have usually been made by electrochemical and electrophoretic deposition and in some cases involved the electrochemical exfoliation of 2D materials such as graphene and layered double hydroxides (LDH). We are currently involved in the application of light polymer-based containers for the storage of hydrogen under high pressures.

 

(4)        Liu, L.; Mandler, D. Using nanomaterials as building blocks for electrochemical deposition: A mini review. Electrochem. Commun. 2020, 120, 6.

(5)        Ouyang, Y.; Geuli, O.; Hao, Q. L.; Mandler, D. Controllable Assembly of Hybrid Electrodes by Electrophoretic Deposition for High-Performance Battery-Supercapacitor Hybrid Devices. ACS Appl. Energ. Mater. 2020, 3, 1784-1793.

(6)        Ouyang, Y.; Ye, H. T.; Xia, X. F.; Jiao, X. Y.; Li, G. M.; Mutahir, S.; Wang, L.; Mandler, D.; Lei, W.; Hao, Q. L. Hierarchical electrodes of NiCo2S4 nanosheets-anchored sulfur-doped Co3O4 nanoneedles with advanced performance for battery-supercapacitor hybrid devices. J. Mater. Chem. A 2019, 7, 3228-3237.

 

 

The formation of a hybrid supercapacitor based on the electrochemical exfoliation of graphite and the incorporation of a faradaic organic material into NiMn-LDH

From "nano to nano" a new approach in electrochemical deposition 

We have demonstrated that electrochemistry can be used as a means of driving the deposition of nanomaterials. The concept was termed by us: "from nano to nano" which means to begin with well-defined nanomaterials dispersed in the electrolyte and to end with thin coatings and patterns, which maintain the nanometric particulate nature of the dispersion. We have developed two approaches; the first is based on changing the pH on the electrode surface, while the second comprises the electrochemically induced increasing the ionic strength. In both mechanisms, the electrical potential causes eventually a decrease of inter-particle repulsions. The figure below shows one of our recent successes in which a wide range of 1-3D nanomaterials, i.e., VO₂ and Au nanoparticles, carbon nanotubes and graphene oxide, were successfully deposited.

 

 

The "nano to nano" approach based on the electropolymerization of EDOT that is strongly bound to NbOPO₄ nanoparticles for the deposition of nanomaterials

 

Electrochemistry with high resolution

This topic started with scanning electrochemical microscopy (SECM) where Mandler was one of the pioneers using this technique for patterning surfaces. We have used SECM for carrying out a wide range of surface modifications, such as metal deposition and etching, and studying electron transfer processes, e.g., in conducting polymer and electrochromic materials. Specifically, we have recently focused on the local deposition of nanomaterials such as metallic and other nanoparticles. We have shown that SECM can be used for local deposition and shape control of nanostructures. In principle, the general concept was to use electrochemical probes to locally deposit nanostructures under conditions, which will result in anisotropic growth. We suggested a few approaches that are schematically depicted in the figure below. We have shown that it is possible to control the local formation of different anisotropic nanoparticles by introducing either self-assembled monolayers, surfactants to the solution, or an enzyme that catalyzes the reduction of the metal ions. At present, we are trying to combine electrochemistry and printing. This is very ambitious and we currently use other scanning probe microscopy methods.

 

 

Different gold nanostructures locally deposited by SECM

Coating of medical implants

we have been involved for many years in functional coatings and in particular coating of medical implants such as stents and orthopedic implants. Recently, we collaborated with Prof. Noam Eliaz from Tel Aviv University and focused on the electrochemical coating of titanium-based orthopedic implants by hydroxyapatite (HAp). We have succeeded in developing new approaches for the electrochemical deposition of hydroxyapatite nanoparticles by applying moderate potentials to negatively charged HAp nanoparticles. In addition, we have been able to incorporate different antibiotics into nanoparticles to accommodate, for the first time, drugs or in the course of electrochemical deposition. More recently, we have started working on PEEK and modified it with ZnO nanoparticles embedded in a sol-gel matrix.

 

 

TEM images and EDXcolor mapping of ZnO/MTEOS coating on s-PEEK

Solar thermal energy 

We collaborated for many years with Prof. Shlomo Magdassi from the Hebrew University and BrightSource in developing a stable and highly efficient solar thermal coating for mid-temperature (ca. 500-700 °C). The largest CSP located in Ivenpah, California uses this coating. More recently, we started working on antisoiling coatings for the heliostats and PVs. We focus on the spontaneous formation of topological hydrophobic structures as a means of repelling dust and improving its self-cleaning properties.

 

 

 

Hydrophobic microstructures formed on a mirror for increasing the antisoiling activity.

 

Forensic science 

We have been involved for a long time in forensic science. Our activities are mostly focused on the visualization of latent fingerprints. We have developed with Prof. Joseph Almog (the former head of the Forensic and Identification Department of the Israel Police) a very efficient approach for fingerprint visualization on wet paper (where amino acids are washed away). The method is based on the selective incorporation of gold nanoparticles in the sebaceous ridges or in the hydrophilic valley (where the paper is) depending on the capping agents of the nanoparticles. These metallic particles catalyze the electroless deposition of silver. More recently, we applied a different approach for the visualization of fingerprints on (fired) cartridges.

 

 

 

Developed latent fingerprints on unfired (left) and fired (right) cartrides.

 

Salt bricks

A fascinating project that aims at replacing cement bricks and blocks with elements made of salt. We have developed a green approach carried out at room temperature for the formation of different structures such as bricks, blocks and tiles by pressing a formulation that contains more than 95% sodium chloride. The resulting structures are extremely strong, can be machined and made hydrophobic and have a density that is substantially lower than concrete. Will salt replace cement as a building material? We believe that it can.

 

 

 

Structures made of salt by compression.

 

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