Dipendra Dahal

Bio: Dipendra Dahal is an academic researcher from University of Akron. The author has contributed to research in topics: Plasmon & Graphene. The author has an hindex of 9, co-authored 28 publications receiving 280 citations. Previous affiliations of Dipendra Dahal include University of Maryland, Baltimore & City University of New York.

Progress in Tuning Emission of the Excited-State Intramolecular Proton Transfer (ESIPT)-Based Fluorescent Probes

Abstract: In this review, we will summarize our recent progress in the design and application of novel organic sensors with emission in the near-infrared region (600-900 nm). By coupling different functional groups with excited-state intramolecular proton transfer (ESIPT) segments, new probes are developed to achieve a large Stokes shift, high sensitivity, and selectivity and to tune the emission toward the near-infrared region. The developed probes exhibit attractive optical properties for bioimaging and environmental science applications. In addition, we further discuss the photophysical properties of ESIPT dyes and how their fluorescence could be affected by structural/environmental factors, which should be considered during the development of robust ESIPT-based fluorescence probes. Their potential applications as imaging reagents are illustrated for intracellular membranes, mitochondria, lysosomes, and some biomolecules.

An NIR-emitting ESIPT dye with large stokes shift for plasma membrane of prokaryotic (E. coli) cells

Abstract: A near infrared-emitting cyanine with a very large Stokes shift (Δλ ≈ 230 nm) was synthesized by coupling with excited state intramolecular proton transfer (ESIPT). Fluorescence response of the probe was examined at different pH and at different temperatures, which revealed the important role of ESIPT in the fluorescence. In comparison with commercial FM1-43 (ϕ fl ≈ 0.03 in CH 2 Cl 2 ), which is a popular styryl dye for membrane staining, the developed new probe 2a exhibited a significantly higher quantum yield (ϕ fl ≈ 0.34 in CH 2 Cl 2 ), attributing to the effective intramolecular hydrogen bonding which is present in the latter. In addition, the probe exhibited very good selectivity for imaging plasma membrane of prokaryotic cells, indicating its potential for imaging membrane of procaryotic ( E. coli ) cells.

Quantum-statistical theory for laser-tuned transport and optical conductivities of dressed electrons in α -T 3 materials

Abstract: In the presence of external off-resonance and circularly polarized irradiation, we have derived a many-body formalism and performed a detailed numerical analysis for both the conduction and the optical currents in $\ensuremath{\alpha}\ensuremath{-}{\mathcal{T}}_{3}$ lattices. The calculated complex many-body dielectric function as well as conductivities of displacement and transport currents display strong dependence on the lattice-structure parameter $\ensuremath{\alpha}$, especially approaching the graphene limit with $\ensuremath{\alpha}\ensuremath{\rightarrow}0$. Unique features in dispersion and damping of plasmon modes are observed with different $\ensuremath{\alpha}$ values, which are further accompanied by a reduced transport conductivity under irradiation. The discovery in this paper can be used for designing novel multifunctional nanoelectronic and nanoplasmonic devices.

NIR-Emitting Hemicyanines with Large Stokes’ Shifts for Live Cell Imaging: from Lysosome to Mitochondria Selectivity by Substituent Effect

Abstract: Lysosome imaging without perturbing intracellular activity remains challenging, as the current commercial lysosome probes contain weakly basic amino groups that could perturb lysosome pH. Herein, w...

Excited-state intramolecular proton-transfer (ESIPT) based fluorescence sensors and imaging agents

Abstract: In this review we will explore recent advances in the design and application of excited-state intramolecular proton-transfer (ESIPT) based fluorescent probes. Fluorescence based sensors and imaging agents (probes) are important in biology, physiology, pharmacology, and environmental science for the selective detection of biologically and/or environmentally important species. The development of ESIPT-based fluorescence probes is particularly attractive due to their unique properties, which include a large Stokes shift, environmental sensitivity and potential for ratiometric sensing.

Highly confined low-loss plasmons in graphene-boron nitride heterostructures

Abstract: Graphene plasmons were predicted to possess ultra-strong field confinement and very low damping at the same time, enabling new classes of devices for deep subwavelength metamaterials, single-photon nonlinearities, extraordinarily strong light-matter interactions and nano-optoelectronic switches. While all of these great prospects require low damping, thus far strong plasmon damping was observed, with both impurity scattering and many-body effects in graphene proposed as possible explanations. With the advent of van der Waals heterostructures, new methods have been developed to integrate graphene with other atomically flat materials. In this letter we exploit near-field microscopy to image propagating plasmons in high quality graphene encapsulated between two films of hexagonal boron nitride (h-BN). We determine dispersion and particularly plasmon damping in real space. We find unprecedented low plasmon damping combined with strong field confinement, and identify the main damping channels as intrinsic thermal phonons in the graphene and dielectric losses in the h-BN. The observation and in-depth understanding of low plasmon damping is the key for the development of graphene nano-photonic and nano-optoelectronic devices.

Bright Aggregation-Induced-Emission Dots for Targeted Synergetic NIR-II Fluorescence and NIR-I Photoacoustic Imaging of Orthotopic Brain Tumors

Abstract: Precise diagnostics are of significant importance to the optimal treatment outcomes of patients bearing brain tumors. NIR-II fluorescence imaging holds great promise for brain-tumor diagnostics with deep penetration and high sensitivity. This requires the development of organic NIR-II fluorescent agents with high quantum yield (QY), which is difficult to achieve. Herein, the design and synthesis of a new NIR-II fluorescent molecule with aggregation-induced-emission (AIE) characteristics is reported for orthotopic brain-tumor imaging. Encapsulation of the molecule in a polymer matrix yields AIE dots showing a very high QY of 6.2% with a large absorptivity of 10.2 L g-1 cm-1 at 740 nm and an emission maximum near 1000 nm. Further decoration of the AIE dots with c-RGD yields targeted AIE dots, which afford specific and selective tumor uptake, with a high signal/background ratio of 4.4 and resolution up to 38 µm. The large NIR absorptivity of the AIE dots facilitates NIR-I photoacoustic imaging with intrinsically deeper penetration than NIR-II fluorescence imaging and, more importantly, precise tumor-depth detection through intact scalp and skull. This research demonstrates the promise of NIR-II AIE molecules and their dots in dual NIR-II fluorescence and NIR-I photoacoustic imaging for precise brain cancer diagnostics.

Recent developments in the construction and applications of platinum-based metallacycles and metallacages via coordination

Abstract: Coordination-driven suprastructures have attracted much interest due to their unique properties. Among these structures, platinum-based architectures have been broadly studied due to their facile preparation. The resultant two- or three-dimensional (2D or 3D) systems have many advantages over their precursors, such as improved emission tuning, sensitivity as sensors, and capture and release of guests, and they have been applied in biomedical diagnosis as well as in catalysis. Herein, we review the recent results related to platinum-based coordination-driven self-assembly (CDSA), and the text is organized to emphasizes both the synthesis of new metallacycles and metallacages and their various applications.