Research activities – Daniel Mandler

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:

1. 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. 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.

Silica nanoparticles of different sizes in nanovoids

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

2. Energy storage (supercapacitors, batteries and hydrogen) – This is a topic, which we entered approximately five 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” approach and collaborated with the group of Prof. Hao at Nanjing University of Science 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).

Energy Storage

The formation of a hybrdid supercapacitor based on the electrochemical exfoliation of graphite

3. From "nano to nano" a new approach in electrochemical deposition – We have recently 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 electrochemical induced increasing the ionic strength. In both mechanisms, the electrical potential causes eventually the 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.

Figure 3-Electrochemical induced deposition of nanomaterials by increasing the ionic strength

The "nano to nano" approach based on altering the ionic strength was used for the deposition of nanomaterials.

4. 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 deposition 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 catalyzed 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.
Local deposition of different nanostructures by SECM

Different gold nanostructures locally deposited by SECM

5. 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 have collaborated with Prof. Noam Eliaz from the Tel Aviv University and focused on the electrochemical coating of titanium based orthopedic implants by hydroxyapatite (HAp). We have succeeded to develop new approached for the electrochemical deposition of hydroxyapatite nanoparticles by applying moderate potentials to negatively charged HAp nanoparticles. The essence is depicted below. 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.
Medical implants

6. Electroanalytical chemistry - …

7. Solar thermal energy - .....

8. Forensic science – ....

9. Salt bricks -