Saumyakanti Khatua

D-Band hole extraction is a rate-limiting step in plasmonic photocatalysis. Stronger metal–ligand electronic coupling accelerates hole transfer, suppresses recombination, and enhances overall photocatalytic efficiency.

Electro-activated Ni BDC/NF as a dual-purpose electrocatalyst for the valorization of lignocellulose-based small molecules and the upgradation of mixed plastic wastes into commercial chemicals along with concurrent H ₂ generation.

We demonstate wavelength specific modulation of plasmonic catalysis using selected ligands.

Nanoparticles have been of significant interest in various biomedical domains such as drug delivery, gene delivery, cytotoxicity analysis, and imaging. Despite the synthesis of a variety of nanoparticles, their cellular uptake efficiency remains a substantial obstacle, with only a small fraction of delivered nanoparticles (NPs) have been reported to traverse the cell membrane within 24 h. Consequently, higher doses are often necessitated, leading to increased toxicity concerns. In this investigation, we illustrate that nanoparticles having negative Gaussian curvature demonstrate rapid and efficient internalization into cells by lowering the energy barrier for membrane bending. Specifically, three types of gold nanoparticles; gold nanorods (GNR), gold nanodogbones at pH 4 (GDB4), and gold nanodogbones at pH 6 (GDB6) were synthesized, with Gaussian curvatures of 0, -166.91, and -376.62, respectively. Cellular uptake studies conducted via ICP-OES analysis reveal that GDB6 is taken up 140% more in A549 cells and 77% more in NIH3T3 cells compared to GNR. Confocal microscopy-based uptake studies further confirm the higher uptake of GDB6 compared to GNR. Additionally, molecular simulations indicate that GDB nanoparticles exhibit a significantly larger free energy change during translocation compared to GNR, emphasizing the impact of nanoparticle shape on uptake and translocation through the membrane and validating the efficacy of negative Gaussian curvature in enhancing cellular uptake, consistent with experimental observations. Overall, our findings emphasize the importance of nanoparticle curvature modulation in maximizing cellular uptake efficiency for improved biomedical applications, providing valuable insights into the design of nanomaterials for drug delivery purposes.

Sulfur dots (S-QDs) hold promise as a new category of metal-free, luminescent nanomaterials, yet their practical application faces challenges primarily due to a limited understanding of their structure and its impact on their optical properties. Herein, by employing a spectrum of aliphatic and aromatic ligands, we identify the surface structure and composition of S-QDs while delineating the pivotal role of ligands in inducing photoluminescence. Thiol-functionalized ligands, such as 4-mercapto benzoic acid and glutathione, notably promote the formation of both green and blue luminescent S-QDs, boosting a high quantum yield of up to 56%. Further investigation on the synthesis of S-QDs with 4-mercapto benzoic acid unveils the dual role of H₂O₂: etching sulfur powder and oxidizing the –SH group to –SO₂H. These oxidized ligands passivate the S-QD surface through hydrogen bonding. Electrospray ionization mass spectrometry analysis unveils the presence of distinct sulfur species such as [S₄(C₆H₅SO₂H)₄(H₂O)₂H]⁺ and [S₆(C₆H₅SO₂H)₆(H₂O)₃H]⁺, while XPS analysis confirms the existence of zerovalent sulfur and oxidized sulfur species including SO₃ ²⁻ and SO₄ ²⁻. Further detailed spectroscopic examination demonstrates that S-QDs predominantly exist as aggregated entities, with the emission wavelength correlating with the degree of aggregation. The absence of photoluminescence in aggregations devoid of ligands underscores the critical role of ligands in the photoluminescence genesis of S-QDs.

The development of robust and efficient photocatalytic constructs for boosting the water oxidation reaction (WOR) is needed for establishing a sunlight-driven renewable energy infrastructure. Here, we synthesized plasmonic core–shell nanoconstructs consisting of triangular gold nanoprism (AuTNP) core with mixed manganese oxide (MnOx) shell for photoelectrocatalytic WOR. These constructs show electrocatalytic WOR with a low onset overpotential requirement of 270 mV at pH 10. Photoexcitation showed further enhancement of their catalytic activity resulting in ∼15% decrease of the onset overpotential requirement along with the generation of photocurrent density of up to 300 μA/cm2. We showed that such light-driven enhancement of AuTNP@MnOx dyad’s catalytic activity toward the WOR process includes contributions from both photocatalytic (hot carriers driven) and photothermal effects with photothermal effect playing the major role for wavelength between 532 and 808 nm. The contribution from the photocatalytic effect is appreciable only for high-energy excitations near the interband region, while the photothermal effect largely dominates for lower energy excitations near the LSPR wavelengths of the dyad.