Research areas

Our research vision is to explore physical chemistry of biological systems or bio-inspired artificial systems to achieve high performance devices with intelligent design in order to respond to the climate change (mitigation and adaptation). Our research area is highly interdisciplinary emcompassing physics, chemistry and biology. To explore these systems, we use primarily ultrafast transient absorption (TA) spectroscopy, time resolved fluorescence spectroscopy and microscopy.

In terms of advance tool development, our focus will be to develop pump-probe microscopy technique, which has been around for some time but not explored yet to its full potential and only available to very few groups around the world. This technique will provide us both spatial (submicron resolution, ≤ 1 mm) and temporal resolution (~ 100 fs, can be improved further depending on the problem to be addressed). This tool will help us to answer many challenging questions related to various photophysical processes.

Research area 1: Investigation of the molecular mechanism of photosynthesis in plants/algae inside near-native environment or intact cells

Effective regulation of energy flux in response to changing light conditions is necessary for plants to avoid photodamage and optimize growth. Antenna proteins play a crucial role in these regulatory mechanisms, being able to switch between light harvesting state and dissipative state (carrying out photoprotection by safely dissipating excess excitation energy as heat). However, the challenging question that need to be addressed:

How does photoprotection mechanism work (at molecular level)?

Although many studies have addressed this question, the answer is still debated because of the technical challenges of the measurements, as current data are often limited to in vitro and in silico studies. The photophysical studies on light harvesting complexes (LHCs) are typically performed on isolated complexes extracted from intact systems and solubilized using detergents. Unfortunately, detergents provide a local environment that is dramatically different with respect to that of the thylakoid membrane. Measurements on isolated complexes do not capture the behavior of the in vivo system as it lacks the full complexity of the intact system with its various feedback loops, sensing/activating proteins (e.g., PsbS or LHCSR/LHCX), and protein–protein interactions, along with pH and ionic gradients. The available literature on TA measurements of live cells is limited as in vivo spectroscopy is hindered by strong scattering and by the presence of many spectrally overlapping signals. Thus, the holistic picture of this field is still missing. We strongly believe that compared to conventional TA, the pump-probe microscopy on live cells would be able to provide better insights on the complex photosynthetic mechanisms. To the best of our knowledge, this approach has not been explored so far. Our objectives in this research area are to investigate the photosynthesis mechanism by using nanodiscs, which are discoidal lipid bilayer membranes, mimicking the near-native membrane environment (i.e. to improve the model system) as well as intact chloroplasts/cells (real systems).

Selected publications:

[1] S. Sardar et al., Journal of Physics: Photonics 2026, 8, 012002.

[2] P. Saraceno, S. Sardar et al., Journal of Physical Chemistry Letters 2024, 15, 6398–6408.

[3] S. Sardar et al., Journal of Physical Chemistry Letters 2024, 15, 3149–3158.

[4] A. G. Fleitas, S. Sardar* et al., Journal of the Royal Society Interface 2024, 21, 20230676. (*S. Sardar as corresponding author)

[5] S. Cazzaniga et al., Plant Physiology 2023, 193, 1365.

[6] S. Sardar et al., J. Chem. Phys 2022, 156, 205101.

Research area 2: Photophysics of emerging materials

Sunlight is the most abundant renewable energy resource, which is harvested for the generation of chemical energy by nature using evolved complex photosynthetic processes that we aim to explore as described in the previous research area. The development of novel functional materials and devices to harvest and convert solar energy has been recognized as an important step to sustainable energy resources and to meet the rising energy demand. Notably, charge transfer or separation at the interface is a crucial aspect, which determines the efficiency of light harvesting across the heterojunctions and consequently surface reactions. The main objective of this research area is to investigate the molecular processes involving light harvesting and energy conversion using ultrafast spectroscopy on the newly developed functional materials and devices. A better understanding of photoinduced processes will lead to new strategies for improving the catalytic activity of the nanohybrids.

Selected publications:

[1] S. Ghosh, S. Bera, S. Sardar et al., ACS Applied Materials & Interfaces 2023, 15, 18867.

[2] E. Cinquanta, S. Sardar et al., Nano Letters 2022, 22, 1183–1189.

[3] S. Sardar et al., Nanotechnology Reviews 2016, 5, 113.

[4] S. Sardar et al., Scientific Reports 2015, 5, 17313.

[5] S. Sardar et al., Solar Energy Materials and Solar Cells 2015, 134, 400.

[6] S. Sardar et al., Physical Chemistry Chemical Physics 2013, 15, 18562.

Research area 3: Physical chemistry of biotic/abiotic interface using multidimensional approach

In this research direction, we aim to understand the biotic/abiotic interface (interaction of live cells with materials based on nanomaterials/conjugated polymers) using multidimensional approach. In particular, recently, the possibility to optically trigger the electrical activity of living cells both in-vitro and in-vivo has gained tremendous interest and fuelled multidisciplinary research involving several scientific communities such as biotechnology, neuroscience, biophysics and biomaterials. Light controlled cell manipulation has several advantages compared to more traditional electrical stimulation, such as the possibility to achieve unprecedented spatial and temporal resolution, reduced invasiveness and selectivity. The cell membrane is the natural target for this approach. In particular, membrane potential modulation occurs via the photoinduced modification of the cell membrane electrical properties, such as resistance, capacitance and resting potential, either through direct photostimulation or by using selected transducers that are able to convert light into an electrical, mechanical, chemical, or thermal stimulus. Thus, perturbing the membrane is a fundamental way to stimulate a cell. We aim to unravel the mechanistic insights using spectroscopic techniques (pump-probe microcopy, live cell nanoscopy and fluorescence probes) in order to understand the processes in detail and to improve the photostimulation process.

Selected publications:

[1] J. Barsotti et al., ACS Applied Materials & Interfaces 2023, 15, 13472.

[2] A. Magni et al., Physical Chemistry Chemical Physics 2022, 24, 8716.

[3] G. Bondelli, S. Sardar et al., Journal of Physical Chemistry B 2021, 125, 10748-10758.

Research area 4: Optoelectronic and Plasmonics based Devices

In this research direction, we aim to fabricate novel hybrid optoelectronic devices, fiber optics based plasmonic devices and their characterization. Reflective (plasmonic) structural coloration, which has attracted significant interest as a solution to avoid inks based on dyes has several advantages include better robustness compared to organic dyes while also providing high chromaticity and brightness in ultrathin films. However, lack of cheap and scalable fabrication techniques has so far limited structural coloration to only a few applications and functional devices. Inkjet printing has potential to provide a solution as the method is flexible, scalable to large areas, and avoids complicated or costly fabrication steps. Recently, we have developed a light-driven mechanical nanopump (NP) on an optical fiber tip designed for active transport of target analytes to the sensor. Here, signal detection and illumination for photothermal heat generation, which drives the NP, occur simultaneously. In the presence of the pumping mechanism, a 4-fold increase in sensitivity was observed compared to the purely photothermal effect, demonstrating the potential of the presented photothermomechanical nanopumps for sensing applications.

Selected publications:

[1] N. Polley, S. Sardar et al., ACS Nano 2023, 17, 1403.

[2] R. Shanker, S. Sardar et al., Nano Letters 2020, 20, 7243.

[3] S. Sardar et al., Journal of Materials Chemistry C 2019, 7, 8698.

[4] E. Kang, S. Chen, S. Sardar et al., ACS Photonics 2018, 5, 4046.

Page updated

Google Sites

Report abuse