Research Areas

Peptide-induced Fusion of Dynamic Membrane Nanodomains: Implications in a viral entry

Enveloped viruses infect host cells via protein-mediated membrane fusion. However, insight into the microscopic rearrangement induced by the viral proteins and peptides has not emerged yet. Here we report a new methodology to extract viral fusion peptide (FP) mediated biomembrane dynamical nanodomain fusion parameter, λ, based on stimulated emission depletion microscopy coupled with fluorescence correlation spectroscopy. We also define another dynamical parameter membrane gradient, defined in terms of the ratio of average lipid diffusion coefficients across dynamic crossover length scales, ξ. Significantly, we observe that λ as well as these mobility gradients, are larger in the stiffer liquid-ordered (Lo) phase compared to the liquid-disordered phase and are more effective at the smaller nanodomain interfaces which are only present in the Lo phase. The results could possibly help resolve a long-standing puzzle about the enhanced fusogenicity of FP in Lo phase. Results obtained from the diffusion results have been correlated with the human immunodeficiency virus (HIV) gp41 fusion peptide-induced membrane fusion.

Spontaneous unbinding transition of nanoparticles adsorbing onto biomembranes: interplay of electrostatics and crowding

Cellular membranes are constantly bombarded with biomolecules and nanoscale particles, and cell functionality depends on the fraction of the bound/internalized entities. Understanding the bio-physical parameters underlying this complex process is very difficult in live cells. Model membranes provide an ideal platform to obtain insight into the minimal and essential parameters involved in determining cell membrane-nanoparticle (NP) interaction. Here we report spontaneous binding and unbinding of semiconductor NPs, carrying different net charges and interacting with model biomembranes, using in-situ neutron reflectivity (NR) and fluorescence microscopy studies. We observe a critical concentration of NPs above which they spontaneously unbind along with lipids from lipid monolayer membranes, leaving behind fewer bound NPs. This critical concentration varies depending on whether the NPs carry a net charge or are neutral, and is also governed by the extent of NP crowding for a fixed NP charge. The observations suggest a subtle interplay between electrostatics, membrane fluidity, and NP crowding effects which eventually determines the adsorbed concentration for unbinding transition. Our study provides valuable microscopic insight into the parameters that could determine the biophysical process underlying NP uptake & ejection by cells which, in turn, can be utilized for their potential application in bioimaging & drug delivery.

Microscopic temperature-dependent structural dynamics in polymer nanocomposites: role of graft-matrix chain interfacial entropic effect.

Polymer and polymer nanocomposite (PNC) melts are known to exhibit a hierarchy of length and time scales. While the length scale dependent structure and dynamics are reasonably well established for polymers, the current status of our understanding on similar properties for PNCs is still far from satisfactory. This is largely due to the interactions between the embedded nanoparticles (NPs) and the matrix chains introduced with the addition of NPs. Moreover, the additional parameters such as the size of NPs and width of interfacial layer (IL) are found to influence its viscoelastic properties. While the structure and dynamics of pristine polymer melts are largely determined by entropic effects in PNCs a strong enthalpic effect is introduced between the NP and the matrix chains. We present a systematic study of the structural dynamics in bulk entropic polymer nanocomposites (PNCs) with deuterated-polymer grafted nanoparticles (DPGNPs) using quasi-elastic neutron scattering (QENS). We observe that the wave vector-dependent relaxation dynamics depend on the entropic parameter, f , and the length scale being probed. The entropic parameter can be defined in terms of the grafted-to-matrix polymer molecular weight ratio and controls the extent of matrix chain penetration into the graft. Dynamical cross-over from Gaussian to non-Gaussian behavior at wave vector, Qc, which depends on temperature and f , was observed. Further insight into the underlying microscopic mechanism responsible for the observed behavior revealed that when interpreted with a jump-diffusion model, in addition to the speeding-up in local chain dynamics, the elementary distance over which sections of the chain hop is strongly dependent on f . Interestingly, we also observe dynamic heterogeneity (DH) in the studied systems, characterized by the non-Gaussian parameter, α2, which reduces for high- f ( f = 0.225) sample as compared to the pristine host polymer, indicating reduced dynamical heterogeneity, while it is mostly unchanged for the low- f sample. The results highlight that, unlike enthalpic PNCs, entropic PNCs with DPGNPs can modify the host polymer dynamics owing to the subtle balance of interactions occurring at different length scales in the matrix.

References: Swain, Aparna, Nimmi A. Das, Victoria Garcia Sakai, and Jaydeep Kumar Basu. “Microscopic temperature-dependent structural dynamics in polymer nanocomposites: role of graft-matrix chain interfacial entropic effect.” Soft Matter, 2023,19, 5396-5404.

Enhanced efficiency of water desalination in nanostructured thin-film membranes with polymer grafted nanoparticles.

Reverse osmosis (RO) is a key energy-efficient and cost-effective desalination protocol, and thus, there has been considerable attention towards the development of membranes with improved separation performance. Thin film composite polyamide (TFC-PA) membranes are the state-of-the-art ubiquitous platforms to desalinate water at scale. Recently, surface modification has become a popular approach for improving the desalination performance of the popular class of PA membranes. In particular, anchoring a hydrophilic PA layer on to the membrane surface via physical adsorption, or polymer grafting (“grafting to” and “grafting from”) is efficacious in improving performance, while aiding in antifouling and dye rejection. While recent studies have explored ways of improving perm-selectivity, achieving precise separation of ions and small molecules requires enhancing pore size homogeneity, which entails a paradigm shift in engineering the PA active layer. Here, we demonstrate the fabrication of an ultra-selective TFC- PA membrane with remarkable salt rejection performance even at desirably large water flux. We have developed a novel, transformative platform where the performance of such membranes is significantly and controllably improved by depositing thin films of polymethylacrylate [PMA] grafted silica nanoparticles (PGNPs) through the venerable Langmuir-Blodgett method. Our key practically important finding is that these constructs can have unprecedented selectivity values (i.e., ∼ 250-3000 bar−1, > 99.0% salt rejection) at reduced feed water pressure (i.e., reduced cost) while maintaining acceptable water permeance A (=2-5 Lm−2 hr−1 Bar−1) with as little as 5-7 PGNP layers. We also observe that the transport of solvent and solute are governed by different mechanisms, unlike gas transport, leading to independent control of A and selectivity. Since these membranes can be formulated using simple and low cost self-assembly methods, our work opens a new direction towards development of affordable, scalable water desalination method.

Reference: Swain, Aparna, S. Adarsh, Ashish Biswas, Suryasarathi Bose, Brian Benicewicz, Sanat Kumar, and Jaydeep Kumar Basu. “Enhanced efficiency of water desalination in nanostructured thin-film membranes with polymer grafted nanoparticles.” Nanoscale, 2023, 15, 11935 – 11944.


Postdoc: – University of Pennsylvania Chemistry department Philadelphia, Pennsylvania USA

PhD scholar at TU Delft Physics department Netherlands

PhD scholar at Indian Institute of Science Bangalore Physics department India

Prof. Brian C. Benicewicz Professor of Chemistry, University of South Carolina, USA

Prof. Suryasarathi Bose Professor, Materials Engineering, Indian Institute of Science Bangalore, India

Prof. Sanat K Kumar Professor of Chemical engineering, Columbia University, New York USA

Prof. Jaydeep kumar basu Professor of Physics, Indian Institute of Science Bangalore, India

Spontaneous Formation and Kinetics of Lipid Nanotubules induced by Passive Nanoparticles

Cell membrane is an interesting self-assembled soft matter system that undergoes myriad of shape deformations and facilitates different cellular functions. Lipid nanotubules have been observed to promote transport of cellular cargos as well as facilitate intra and intercellular communication. It has also been reported to play crucial role in spread of infection as well as possess therapeutic functionalities. Hence, there has been a growing interest in understanding the initiation and subsequent kinetics of evolution of tubules using motor proteins, antimicrobial peptides, polymers and nanoparticles. Interesting spectrum of tunability of the properties of nanoparticles and supported lipid bilayer platform opens up the window of control parameters in initiating/inhibiting tubule formation, accelerate/slow down the kinetics of tubulation process etc.


Employing CdSe-ZnS quantum dots (QDs) on simple mixtures of DLPC: DPPC supported lipid bilayers (SLBs), different stages of evolution of lipid tubules such as tubule initiation, saturation and retraction has been captured across different membrane compositions. Analysis of tubulation kinetics suggests much faster initiation and faster growth velocity in case of heterogeneous two component membrane and a delayed response in case of fluidic single component SLB influenced by the flexibility in membrane packing. Similarly, concentration has also been observed to determines the kinetics such that low concentration results in slower kinetics. Further, time dependent analysis of persistent length of tubes suggests non-monotonic changes in the mechanical property of tubules driven by binding-unbinding of QDs on the tubes. Interestingly, the most flexible tubes were observed in case of 2 component SLBs and most stiffer tubes for the fluidic SLB. Hence, these results suggest some simple insights on complicated processes such as arrest of infection, prevention of specific inter or intra-cellular communication, restoring malfunctioning organelles through artificial restoration of tubulation.

Reference: Roobala Chelladurai, Koushik Debnath. Nikhil R. Jana and Jaydeep K. Basu Spontaneous formation and growth kinetics of lipid nanotubules induced by passive nanoparticles, Soft Matter, Just Accepted, 10.1039/D2SM00900E

Selectively strong coupling of MoS2 excitons to a metamaterial at room temperature

Hyperbolic metamaterial (HMM) is a metal-dielectric composite metamaterial. The momentum space envelope of HMM states is a hyperboloid, which ensures that the total states available inside the HMM are practically infinite. The hyperbolic behaviour is seen, after a set-in point (OTT). At OTT electric field is huge and reduces sharply with lowering energy. The inbuilt field gradient of HMM can be used to selectively couple light emitters.

Light from monolayer Molybdenum disulphide (MoS2) is ideally oriented to interact with the HMM states. The MoS2 monolayer emits light at two energies, at 2 eV (B exciton) and 1.83 eV (A exciton). We have transferred MoS2 on HMM with OTT at 2.1 eV. We find that the B excitons are strongly coupled to HMM states, where as the A excitons are not strongly coupled. The B excitons lose their identity and become hybrid light-matter states called Polaritons.

The HMM is made through anodizing and silver electroplating of Aluminium, which are common metal finishing industry processes. HMM is scalable and functions as an energy selective coupler for multi-excitonic systems as MoS2. Also due to the direct bandgap of MoS2, the polaritons can be directly encoded, by modulation input of a resonant laser diode.

For more information:

Modulation of live bacterial membrane dynamics upon antibiotic treatments at sub lethal doses might play a vital role in acquiring multi-drug resistance.

Antibiotic resistance is a worldwide concern due to widespread misuse of antimicrobial drugs at improper doses, which strongly reduced their clinical efficacy through the selection of resistant bacteria. The mechanisms of antimicrobial resistance exhibited by drugs are broadly grouped into three categories, i) drug inactivation ii) modification of the binding site of drug molecules, and iii) modification of lipid membrane properties. Among the above-mentioned mechanisms, modification in the bacterial cell envelope is quite important to generate resistance in bacteria. Therefore, understanding the interaction of such membrane targeting antibiotics with the bacterial cell envelope at the molecular level should give us additional insight into antimicrobial action and its resistance mechanism. Similarities and variations observed between a membrane targeting antibiotic as well as a non-membrane targeting antibiotic will reveal the intricacies behind membrane specificity.

Our work on live E. coli cell envelope explores the two major physical parameters, membrane lipid diffusion coefficient and cell surface roughness using confocal-fluorescent correlation spectroscopy (FCS) and atomic force spectroscopy (AFM) respectively. Upon treating the E. coli K12 bacterial cells with colistin, a membrane targeting antibiotic and ciprofloxacin (CPX), a non-membrane targeting drug, we observed elongated or filamented cells.  The filamentation is prominent in case of CPX treated cells because of its ability to induce SOS response. Our results suggest that the extent of elongation is uncorrelated with the changes observed in the lipid dynamics. However, a factor of two increase in the lipid diffusion coefficients (D) of the antibiotic treated cells indicating that there was significant effect of a non-membrane targeting CPX on the bacterial membrane which was comparable to a membrane targeting colistin. FCS on inner membrane preferring FM4-64 dye indicated the altered lipid properties in both inner as well as outer membrane of the E. coli.

We were able to eliminate the possibility of correlation between growth kinetics, cell elongation and lipid dynamics, which left us with two other possibilities to explain the observed changes in lipid diffusion. The change in diffusivities could be attributed to an outcome of direct interaction between antibiotic molecules on the membrane or an indirect consequence of disruptions in lipid biosynthetic pathways. Surface roughness measurements from AFM images suggest that the D values are in fact a result of direct interaction of the colistin on the cell envelope. Although CPX treated cells had increased surface roughness, it was comparatively less, making it a fascinating challenge to identify if there exists a hidden cause behind enhanced lipid D in addition to the direct interaction.

For more information:

[a] Ponmalar, I. I., Swain, J., & Basu, J. K. (2022). Escherichia coli response to subinhibitory concentration of Colistin: Insights from study of membrane dynamics and morphology. 
Biomater. Sci. DOI

[b] Ponmalar, I. I., Swain, J., & Basu, J. K. (2022). Modification of bacterial cell membrane Dynamics and morphology upon exposure to sub inhibitory concentrations of ciprofloxacin. Biochimica et Biophysica Acta (BBA)-Biomembranes, 183935.

Lipid dynamics influenced by oligomeric states a typical pore forming toxin Listeriolysin O: Interplay between lipid free area and crowding

Developing alternate strategies against pore forming toxin (PFT) mediated bacterial virulence factors require an understanding of the cellular membrane response. Membrane-bound protein complexes involving PFTs, released by virulent bacteria are known to form pores leading to host cell lysis. However, membrane disruption and related lipid reorganization events during attack by PFTs remain largely unexplored which became the focus of our study.

In order to study the influence of LLO pore formation on lipid dynamics in a more controlled environment, experiments were carried out on SLBs over a range of LLO concentration, Cp. In a homogeneous lipid bilayer system (DOPC:Chol:3:1) as well as Ld domain of a phase separated, DOPC:DPPC:Chol::2:2:1, bilayer[2]. Here, we have reported counter intuitive and non-monotonic variations in lipid diffusion, measured using confocal FCS, due to interplay of lipid ejection and crowding by membrane bound oligomers of LLO. Lipid diffusion was observed to have an initial enhancement followed by a gradual decline upon increasing Cp. The observed protein concentration dependent dynamical cross-over is correlated with transitions of LLO oligomeric state populations from rings to arc-like pore complexes, predicted using a proposed two-state free area based diffusion model. At low Cp, a hitherto unexplored regime of increased lipid diffusivity is attributed to lipid ejection events due to a preponderance of ring-like pore states. At higher Cp where membrane inserted arc-like pores dominate, lipid ejection is less efficient and the ensuing crowding results in a lowering of lipid diffusion. These variations in lipid dynamics are corroborated by macroscopic rheological response measurements of PFT bound vesicles.

For more information:

  1. Ponmalar, Ilanila I., Ramesh Cheerla, K. Ganapathy Ayappa, and Jaydeep K. Basu. “Correlated protein conformational states and membrane dynamics during attack by pore-forming toxins.” Proceedings of the National Academy of Sciences 116, no. 26 (2019): 12839-12844.
  2. Ilanila, I. P., K. Ganapathy Ayappa, and Jaydeep K. Basu. “Bacterial protein Listeriolysin O induces non-monotonic dynamics due to lipid ejection and crowding.” Biophysical Journal (2021).

Interplay of lipid packing and charge density in multicomponent, charged model biomembranes tunes permeation and preferential binding of charged Q2 nanoparticles

Cells respond to external stress by altering their membrane lipid composition to maintain fluidity, integrity and net charge. However, in interactions with charged nanoparticles (NPs), altering membrane charge could adversely affect its ability to transport ions across the cell membrane. Hence it is important to understand possible pathways by which cells could alter zwitterionic lipid composition to respond to nanoparticles without compromising membrane integrity and charge. Such insight is best obtained by studying model biomembranes which, however, need to replicate actual cell membranes, especially their compositional heterogeneity and charge. In our recent studies using synchrotron X-ray reflectivity (XR) measurements, we tried to monitor the interaction of cationic NPs, in the form of quantum dots, with phase-separated supported lipid bilayers as well as floating Langmuir monolayers of different compositions.

These compositions were chosen to be composed of an ordered and anionic charged lipid in combination with uncharged but variable stiffness lipids with the intention of understanding how the subtle interplay of zwitterionic lipid packing and anionic lipid charge density can affect cationic nanoparticle penetration and phase specific binding. We observe that the extent of NP penetration into the respective supported lipid bilayers, as estimated from XR data analysis, is inversely related to membrane compression moduli, which was tuned by altering the stiffness of the zwitterionic lipid component. For a particular membrane composition with discernible height difference between ordered and disordered phases, we were able to observe subtle correlations between the extent of charge on the NPs and the specificity to bind to the charged and ordered phase, contrary to that observed earlier for phase-separated model biomembranes containing no charged lipids.

Whereas for unsupported floating Langmuir monolayers, we observed that under identical subphase pH, the membrane with higher anionic charge density displays higher NP penetration. We also observe coalescence of charged lipid rafts floating amidst a more fluidic zwitterionic lipid matrix due to the phase specificity of QD binding. For both the monolayer and bilayer systems, we observed that the membrane with the higher charge density of the charged lipid domains causes a higher coverage of charged nanoparticle binding. Our results provide microscopic insight into the role of membrane rigidity and electrostatics in determining membrane permeation. This can lead to great potential benefit in rational designing of NPs for bioimaging, drug delivery applications as well as in assessing and alleviating cytotoxicity of nanoparticles.

For more information, please refer:

Chaudhury, A., Debnath, K., Bu, W., Jana, N. R., & Basu, J. K. (2021). Penetration and preferential binding of charged nanoparticles to mixed lipid monolayers: interplay of lipid packing and charge density. Soft Matter17(7), 1963-1974. DOI: 10.1039/D0SM01945C

Chaudhury, A., Varshney, G. K., Debnath, K., Das, G., Jana, N. R., & Basu, J. K. (2021). Compressibility of Multicomponent, Charged Model Biomembranes Tunes Permeation of Cationic Nanoparticles. Langmuir, 37(12), 3550-3562. DOI: 10.1021/acs.langmuir.0c03408

Hybrid devices consisting of single layer graphene (SLG) and semiconductor quantum dots (QDs) can lead to the formation of optoelectronic devices with enhanced sensitivity and can have extensive applications in the field of the photodetector and photovoltaics. The optical properties of the resultant hybrid material are controlled by the interplay of energy transfer between QDs and charge transfer between the QDs and SLG. By studying the steady-state and time-resolved photoluminescence spectroscopy of hybrid QD−SLG devices, we observe a subtle interplay of short- and long-range energy transfer between cadmium selenide (CdSe) QDs in a compact monolayer solid film placed in close proximity to an SLG and the charge transfer from the QD solid to SLG. At larger separation, δ, between the compact monolayer QD and SLG, the emission properties are dominated by mutual energy transfer between the QDs. At relatively smaller separation the emission from QDs, which is strongly quenched, is dominated by charge transfer between QDs and SLG. In addition, we are also able to tune the relative strength of energy and charge transfer by electrostatic doping through the back gate voltage, which provides a novel pathway to tune emission properties of these devices for possible applications as photodetectors, in photovoltaics, and for sensing.

For more information, see “Electrical Tuning of Optical Properties of Quantum Dot−Graphene Hybrid Devices: Interplay of Charge and Energy Transfer.” Riya Dutta, Saloni Kakkar, Praloy Mondal, Neha Chauhan, and J. K. Basu*.

Room-Temperature Coupling of Single Photon Emitting Quantum Dots to Localized and Delocalized Modes in a Plasmonic Nanocavity Array

Single photon sources, especially those based on solid state quantum emitters, are key elements in future quantum technologies. What is required is the development of broadband, high quantum efficiency, room temperature single photon sources, which can also be tunably coupled to optical cavities, which could lead to development of all optical quantum communication platforms. In this regard, the deterministic coupling of Single photon sources to plasmonic nanocavity arrays has great advantage due to long propagation length and delocalized nature of surface lattice resonances . Guided by these considerations, we report experiments on the room temperature tunable coupling of single photon emitting colloidal quantum dots to localised surface plasmon and surface lattice resonances modes in plasmonic nanocavity arrays. Using time-resolved photoluminescence measurement on isolated colloidal quantum dots, we report significant advantage of surface lattice resonances in realizing much higher Purcell e_ect, despite large dephasing of colloidal quantum dots, with values of ~22 and ~6 for coupling to the lattice and localized modes, respectively. We present measurements on the antibunching of colloidal quantum dots coupled to these modes with g(2)(0) values in the quantum domain, providing evidence for effective cooperative behavior. We present a density matrix treatment of the coupling of colloidal quantum dots to plasmonic and lattice modes enabling us to model the experimental results on Purcell factors as well as on the antibunching. We also provide experimental evidence of indirect excitation of remote colloidal quantum dots mediated by the lattice modes and propose a model to explain these observations. Our study demonstrates the possibility of developing nanophotonic platforms for single photon operations and communications with broadband quantum emitters and plasmonic nanocavity arrays since these arrays can generate entanglement between to spatially separated quantum emitters.

For more information, see  Ravindra Kumar Yadav, Wenxiao Liu,Ran Li, Teri W. Odom, Girish S. Agarwal, and Jaydeep K Basu. Room-Temperature Coupling of Single Photon Emitting Quantum Dots to Localized and Delocalized Modes in a Plasmonic Nanocavity Array. ACS Photonics (2021). DOI:

Temperature-Driven Grafted Nanoparticle Penetration into Polymer Melt: Role of Enthalpic and Entropic Interactions

Polymer nanocomposites (PNCs) are hybrid materials formed by mixing nanoparticles into pure polymers, with amalgamate properties of polymers and nanoparticles, which find synergistic applications in electronic, optical, and biomedical fields. In order to realize these applications, a good homogeneous nanoparticle dispersion is required. So, it is very important to study the penetration and thermal stability of nanoparticles in PNCs. Understanding the fundamentals of nanoparticle (NP) penetration into soft matter systems is indispensable for numerous applications ranging from targeted nanoparticle-based drug delivery to generating hybrid polymer nanocomposite materials. Hence, it is crucial to identify the parameters which control the extent of NP penetration. We study the penetration of polystyrene-grafted Au nanoparticles (PGNPs) into an entropically/enthalpically coupled soft polymer film. The system consists of two layers: ultrathin monolayer of ordered grains of PGNPs on top of a bulk polymer film. To study enthalpic effects on nanoparticle penetration, PGNP monolayer was coupled to two different polymers, polystyrene (PS) and poly(tert-butyl acrylate) (PtBA). When the temperature of the system is increased toward the glass transition temperature of underlying films, the width and extent of penetration of the PGNP layer depends on the Flory−Huggins parameter between the graft chain of the PGNPs and the underlying matrix polymer. In athermal cases (PGNP/PS) (χ = 0), the initially compact monolayer undergoes structural disordering and individual PGNPs penetrate into PS films to form a broad layer. However, in the second case (PGNP/PtBA) (χ ≈ 0.26), unfavourable enthalpic interactions results in PGNPs penetrating together as a monolayer into PtBA leading to the formation of a narrow layer of PGNP. The extent of PGNP penetration is improved upon increasing the entropic and enthalpic compatibility between PGNPs and underlying bulk layer. We have done molecular dynamics simulation studies, where the time evolution of PGNP penetration into a bottom polymer layer is found to be similar to that in experiments.

Nimmi Das A and Swain, A and Begam, N and Bhattacharyya, A and Basu, JK ,Temperature-Driven Grafted Nanoparticle Penetration into Polymer Melt: Role of Enthalpic and Entropic Interactions” Macromolecules, 53, 8674-8682 (2020).

Observation of photonic spin-momentum locking due to coupling of achiral metamaterials and quantum dots

Chiral interfaces provide a new platform to execute quantum control of light-matter interactions. One phenomenon which has emerged from engineering such nanophotonic interfaces is spin-momentum locking akin to similar reports in electronic  topological materials and phases. While there are reports of spin-momentum locking with combination of chiral emitters and/or chiral metamaterials with directional far field excitation it is not readily observable with both achiral emitters and metamaterials. Here, we report the observation of photonic spin-momentum locking in the form of directional and chiral emission from achiral quantum dots (QDs) evanescently coupled to achiral hyperbolic metamaterials (HMM). Efficient coupling between QDs and the metamaterial leads to emergence of these photonic topological modes which can be detected in the far field. We provide theoretical explanation for  the emergence of spin-momentum locking through rigorous modeling based on photon Green’s function where pseudo spin of light arises from coupling of QDs to evanescent modes of HMM.

For more information, see   Ravindra Kumar Yadav, Wenxiao Liu, SRK Chaitanya Indukuri, Adarsh B. Vasista, G. V. Pavan Kumar, Girish S. Agarwal, and Jaydeep Kumar Basu. Observation of photonic spin-momentum locking due to coupling of achiral metamaterials and quantum dots.Journal of Physics: Condensed Matter, 2020, 33, 015701.


Strongly coupled exciton-surface lattice resonances engineer long-range energy propagation

Achieving propagation lengths in hybrid systems involving plasmonic components beyond typical values of tens of m is important for advancing quantum plasmonics applications. Here we report long-range optical energy propagation in hybrid photonic devices due to excitons in semiconductor quantum dots (SQDs) strongly coupled to surface lattice resonances (SLRs) in a proximal silver nanoparticle array. By using a unique photoluminescence (PL) microscopy scheme we provide evidence for the detection of an exciton-SLR (ESLR) strongly coupled mode at least 600 m away from the region of excitation. We also observe existence of additional energy propagation the range of which goes well beyond that of the ESLR mode and is dependent on the magnitude of strong coupling, g. Cavity quantum electrodynamics (cQED) calculations correctly capture the nature of the experimentally observed PL spectra for consistent values of g, while coupled dipole (CD) calculations show a SQD number dependent electric field decay profile away from excitation region which is consistent with the experimental spatial PL profile. Our results suggest an exciting new direction wherein SLRs or high-quality plasmonic modes can be used to mediate long-range interactions between SQDs, having various possible applications in optoelectronics, sensing and quantum information science.

For more information, see Yadav, Ravindra Kumar, Matthew Otten, Weijia Wang, Cristian L. Cortes, David J. Gosztola, Gary P. Wiederrecht, Stephen K. Gray, Teri W. Odom, and Jaydeep Kumar Basu. "Strongly coupled exciton-surface lattice resonances engineer long-range energy propagation." Nano Letters (2020). DOI: 10.1021/acs.nanolett.0c01236.

Colloidal quantum dot (CQD) assemblies exhibit interesting optoelectronic properties when coupled to optical resonators ranging from Purcell-enhanced emission to the emergence of hybrid electronic and photonic polariton states in the weak and strong coupling limits, respectively. Here, experiments exploring the weak-to-strong coupling transition in CQD–plasmonic lattice hybrid devices at room temperature are presented for varying CQD concentrations. To interpret these results, generalized retarded Fano–Anderson and effective medium models are developed. Individual CQDs are found to interact locally with the lattice yielding Purcell-enhanced emission. At high CQD densities, polariton states emerge as two-peak structures in the photoluminescence, with a third polariton peak, due to collective CQD emission, appearing at still higher CQD concentrations. Our results demonstrate that CQD–lattice plasmon devices represent a highly flexible platform for the manipulation of collective spontaneous emission using lattice plasmons, which could find applications in optoelectronics, ultrafast optical switches, and quantum information science.

For more information, see:

“Room Temperature Weak-to-Strong Coupling and the Emergence of Collective Emission from Quantum Dots Coupled to Plasmonic Arrays.” , Yadav, Ravindra Kumar, Marc R. Bourgeois, Charles Cherqui, Xitlali G. Juarez, Weijia Wang, Teri W. Odom, George C. Schatz, and Jaydeep Kumar Basu.   ACS Nano (2020).  DOI: 10.1021/acsnano.0c02785.