CKN Research Group - dark brackground

Nanoscale Optical & Cellular Imaging Lab

The current research of our group focuses on the fundamental understanding of the photophysical properties of various fluorescent nanomaterials for their applications in optoelectronics, photonics, quantum technology, and in super-resolution microscopic bioimaging. The photophysical properties of these nanomaterials, at first, are deciphered through both ensemble and single-molecule/particle spectroscopy techniques. We rationally design various fluorescent nanomaterials, such as carbon nanodots, graphene quantum dots, coinage metal nanoclusters, composite and alloyed quantum dots and super paramagnetic iron oxide nanomaterials, metal complexes and red emissive organic molecules . We have established a custom-built single-molecule/particle spectroscopy and super-resolution microscopy setup to explore both in vitro and in vivo organelle dynamics, encompassing mitochondria, lysosomes, microtubules, endoplasmic reticulum, and chromatin behavior inside intracellular environment. On the other hand, we are committed to develop room-temperature single-photon sources for quantum technology. We design various composite and alloyed quantum dot materials and their surface engineering for the single photon emission at room temperature. Our multidisciplinary team comprises experts in Chemistry, Physics and Biology. Together, we utilize advanced spectroscopy bulk level steady-state and time-resolved techniques and advanced single molecule/particle microscopic techniques to bring breakthroughs in both fundamental science and practical applications in the fields such as quantum technologies, medical diagnostics, targeted therapies, and beyond.

Single Molecule/Particle Spectroscopy of Nano & Quantum Materials

Single particles and molecules often exhibit inconsistent emission behavior, a phenomenon known as blinking or intermittency

Single-particle/molecule spectroscopy is a technique that focuses on studying individual particle or molecule rather than examining a large ensemble of many particles. This approach eliminates the averaging effects found in ensemble measurements, leading to a clearer understanding of the sample. By using single molecule/particle technique, we understand the deeper insights onto the photophysical properties and their spectral heterogeneity in the sample. In our lab, we have developed a custom-built single molecule/particle spectroscopy setup to study the photophysics of quantum and nanomaterials at the single-particle level. We also utilize fluorescence correlation spectroscopy (FCS), an unique diffusion based technique to further understand the fluorescence properties of the materials. The fluorescence spectroscopic analysis of single particles revealed some exciting phenomena that were previously unknown at the bulk level. The single molecule/particle technique also help in understanding the fluorescence blinking or intermittency, which plays an important role in deciding the fate of the fluorescent material for their optoelectronic applications. Some of the representative research outcome of various nano and quantum materials using single/molecule are presented below.

Deducing the energy level diagram of Carbon Nano Dots in the presence of an electron donor and an electron acceptor

Sci. Rep., 2015, 5 (1), 11423

Single CdTe QDs excited with 488 nm and 532 nm lasers exhibiting excitation-independent single-particle emission statistics

Nanoscale, 2025, 17 (7), 3919-3929

J. Phys. Chem. Lett. 2025, 16, 23, 5868–5877

J. Phys. Chem. Lett. 2020, 11, 14, 5741–5748

Room-Temperature Single Photon Emission

Hanbury-Brown and Twiss (HBT) Setup: Experimental setup to determine the purity of single photon emission

Quantum technologies have the potential to revolutionize various fields, including computing, information processing, sensing, metrology, imaging, cryptography, and communication. These technologies rely on quantum bits, or qubits, which are the quantum analogues of classical bits. Qubits can be implemented using different two-level physical systems, such as superconducting qubits, trapped ion qubits, and photonic qubits. Superconducting qubits use superconducting circuits, trapped ion qubits use atoms or ions, and photonic qubits utilize photons with different colors, phases, or polarizations of photons for qubit generation. Photonic qubits offer several advantages over other types. They can be easily transmitted through optical fibers, are less susceptible to decoherence due to minimal contact with environmental factors, and are a promising candidate for operation at non-zero temperature. In the context of photonic qubits, photons serve as qubits, and single photons are necessary for implementing quantum logic gates and communication protocols.

To realize a photonic qubit, a single photon source is required. A single photon source must generate highly pure single photons on demand with deterministic emission. In our lab, we have utilised colloidal quantum dots to generate single photon with ultra high purity at the room temperature. we are also focused to engineer the single photon emission by various methods involving trap state manipulation via change in core composition