Gold Nanoparticle Based NSET For Monitoring Mg²⁺ Dependent RNA Folding

Understanding the mechanism of how RNA molecules fold into their native structures are vital to their functional properties. Here we report for the first time that gold nanoparticle based NSET can be used for probing the transition states of an RNA unfolding reaction. Our result shows that time-dependent NSET can clearly distinguish structural transitions between unfolded to folded states. Our experimental observation point out that NSET can be used for the design of an optical based molecular ruler to track RNA folding transition states at distances more than double the distances achievable using traditional dipole−dipole Coulombic energy transfer based methods

Gold Nanoparticle-Based Miniaturized Nanomaterial Surface Energy Transfer Probe for Rapid and Ultrasensitive Detection of Mercury in Soil, Water, and Fish

Contamination of the environment with mercury has been an important concern throughout the world for decades. Exposure to high Hg levels can be harmful to the brain, heart, kidneys, lungs, and immune system of humans of all ages. Driven by the need to detect trace amounts of mercury in environmental samples, here we present a miniaturized, inexpensive, and battery-operated ultrasensitive gold nanoparticle-based nanomaterial surface energy transfer probe for screening mercury levels in contaminated soil, water, and fish which has excellent sensitivity (2 ppt) and selectivity for Hg(II) over competing analytes, with the largest fluorescence enhancement to date for sensing Hg(II) in environmental samples (1100-fold). The sensitivity of our probe to detect mercury level in soil, water, and fish is about 2–3 orders of magnitude higher than the EPA standard limit. We demonstrate that our probe is suitable to screen the amount of mercury in different fish, shellfish, and water samples from various commercial sources

Hybrid Graphene Oxide Based Ultrasensitive SERS Probe for Label-Free Biosensing

A metal nanoparticle attached to graphene oxide has the ability to open a new avenue of research with significant opportunities in the biomedical field. In this Letter, we report graphene oxide attached to a popcorn-shaped gold nanoparticle based hybrid SERS probe with ultrasensitive label-free sensing of HIV DNA and bacteria and provide its chemical fingerprint. Our SERS data with the hybrid material shows that it can be used for label-free detection of HIV DNA on the femto-molar level without any labeling. Experimental data with a novel SERS substrate show excellent reproducibility of the SERS signal. The current Letter demonstrates that the label-free SERS detection limit using a hybrid material can be as low as 10 CFU/mL for MRSA bacteria. The possible mechanism for very high sensitivity has been discussed

Gold Nanoparticle Based FRET Asssay for the Detection of DNA Cleavage

We report gold nanoparticle based FRET assay to monitor the cleavage of DNA by nucleases. Fluorescence signal enhancement is observed by a factor of 120 after the cleavage reaction in the presence of S1 nuclease. The mechanism of distant dependent fluorescence quenching has been discussed. Our experimental results on distance dependent fluorescence quenching match quite well with theoretical findings obtained from the fluorescence quenching model by Gersten and Nitzan (Surf. Sci. 1985, 158, 165). Our experimental observation paradigm for the design of optical based molecular ruler strategies at distances more than double the distances achievable using traditional dipole−dipole Columbic energy transfer based methods

Several Orders-of-Magnitude Enhancement of Multiphoton Absorption Property for CsPbX₃ Perovskite Quantum Dots by Manipulating Halide Stoichiometry

Two-photon absorption (2PA) and three-photon absorption (3PA) processes feature many technological applications for fluorescence microscopy, photodynamic therapy, optical data storage, and so on, Herein, we reveal that the giant 2PA and 3PA properties for all-inorganic CsPbX3 (X = Cl, Br, I, and mixed Cl/Br and Br/I) perovskite quantum dots (PQDs) can be enhanced several orders of magnitude, respectively, by simply changing the halide stoichiometry at the X site. Notably, reported data show excellent 2PA and 3PA properties for CsPbI3 (σ2 ∼ 2.1 × 106 GM and σ3 ∼ 1.1 × 10–73 cm8 s3/photon3), which is 2–4 orders of magnitude higher than those of conventional red-emitting QDs and 5–7 orders of magnitude higher than well documented organic molecules. Experimental results show multiphoton absorption (MPA) cross sections can be adjusted 2–3 orders of magnitude by band gap engineering in a predictable manner, via increasing the Pauling electronegativity of the halide. Two-photon luminescence imaging data show that PQDs can be used for very good multiphoton imaging applications. Importantly, reported results provide a new strategy for manipulating MPA properties by halide composition engineering which will be instrumental in the design of next-generation technological devices

Fluorescence Resonance Energy Transfer Based Highly Efficient Theranostic Nanoplatform for Two-Photon Bioimaging and Two-Photon Excited Photodynamic Therapy of Multiple Drug Resistance Bacteria

Near-infrared (NIR) light between 700 and 2500 nm, which is in the range of the first, second, and third biological windows, has the capability to penetrate biological tissues and blood, which provides a huge advantages of higher penetration depth. However, because of the lack of available biocompatible single photon probes in NIR window, there is an urgent need for new theranostic material, which could be used for two-photon bioimaging as well as for two-photon photodynamic therapy (PDT) in biological window. Driven by the need, the current manuscript reports gold nanoclusters (GNCs) attached graphene quantum dot (GQD) based two-photon excited theranostic nanoplatform with high two-photon absorption, very strong two-photon luminescence, as well as two-photon stability in NIR region. Experimental result shows strong two-photon luminescence and two-photon-induced PDT, which is based on fluorescence resonance energy transfer (FRET) mechanism, where graphene quantum dots with very high two-photon absorption act as two-photon donors and gold nanoclusters act as acceptors. Reported data indicate that ¹O₂ generation efficiency enhances tremendously due to the FRET process, which increases the two-photon excited PDT efficiency for multiple drug resistance bacteria (MDRB). Reported data indicate that the nanoplatform has the capability for bright two-photon bioimaging and two-photon photodynamic therapy for MRSA and carbapenem-resistant (CRE) <i>Escherichia coli</i>. Reported nanoplatform is a promising candidate to serve as a contrast agent for multiphoton imaging as well as for two-photon excited PDT agent to eliminate multidrug-resistant strains

Light-Induced Wavelength Dependent Self Assembly Process for Targeted Synthesis of Phase Stable 1D Nanobelts and 2D Nanoplatelets of CsPbI₃ Perovskites

Despite black cubic phase α-CsPbI3 nanocrystals having an ideal bandgap of 1.73 eV for optoelectronic applications, the phase transition from α-CsPbI3 to non-perovskite yellow δ-CsPbI3 phase at room temperature remains a major obstacle for commercial applications. Since γ-CsPbI3 is thermodynamically stable with a bandgap of 1.75 eV, which has great potential for photovoltaic applications, herein we report a conceptually new method for the targeted design of phase stable and near unity photoluminescence quantum yield (PLQY) two-dimensional (2D) γ-CsPbI3 nanoplatelets (NPLs) and one-dimensional (1D) γ-CsPbI3 nanobelts (NBs) by wavelength dependent light-induced assembly of CsPbI3 cubic nanocrystals. This article demonstrates for the first time that by varying the excitation wavelengths, one can design air stable desired 2D nanoplatelets or 1D nanobelts selectively. Our experimental finding indicates that 532 nm green light-driven self-assembly produces phase stable and highly luminescent γ-CsPbI3 NBs from CsPbI3 nanocrystals. Moreover, we show that a 670 nm red light-driven self-assembly process produces stable and near unity PLQY γ-CsPbI3 NPLs. Systematic time-dependent microscopy and spectroscopy studies on the morphological evolution indicates that the electromagnetic field of light triggered the desorption of surface ligands from the nanocrystal surface and transformation of crystallographic phase from α to γ. Detached ligands played an important role in determining the morphologies of final structures of NBs and NPLs from nanocrystals via oriented attachment along the [110] direction initially and then the [001] direction. In addition, XRD and fluorescence imaging data indicates that both NBs and NPLs exhibit phase stability for more than 60 days in ambient conditions, whereas the cubic phase α-CsPbI3 nanocrystals are not stable for even 3 days. The reported light driven synthesis provides a simple and versatile approach to obtain phase pure CsPbI3 for possible optoelectronic applications

Bio-Conjugated Magnetic-Fluorescence Nanoarchitectures for the Capture and Identification of Lung-Tumor-Derived Programmed Cell Death Lighand 1‑Positive Exosomes

As per the American Cancer Society, lung cancer is the leading cause of cancer-related death worldwide. Since the accumulation of exosomal programmed cell death ligand 1 (PD-L1) is associated with therapeutic resistance in programmed cell death 1 (PD-1) and PD-L1 immunotherapy, tracking PD-L1-positive (PD-L1 (+)) exosomes is very important for predicting anti-PD-1 and anti-PD-L1 therapy for lung cancer. Herein, we report the design of an anti-PD-L1 monoclonal antibody-conjugated magnetic-nanoparticle-attached yellow fluorescent carbon dot (YFCD) based magnetic-fluorescence nanoarchitecture for the selective separation and accurate identification of PD-L1-expressing exosomes. In this work, photostable YFCDs with a good photoluminescence quantum yield (23%) were synthesized by hydrothermal treatment. In addition, nanoarchitectures with superparamagnetic (28.6 emu/g), biocompatible, and selective bioimaging capabilities were developed by chemically conjugating the anti-PD-L1 antibody and YFCDs with iron oxide nanoparticles. Importantly, using human non-small-cell lung cancer H460 cells lines, which express a high amount of PD-L1 (+) exosomes, A549 lung cancer cells lines, which express a low amount of PD-L1 (+) exosomes, and the normal skin HaCaT cell line, which does not express any PD-L1 (+) exosomes, we demonstrate that nanoarchitectures are capable of effectively separating and tracking PD-L1-positive exosomes simultaneously. Furthermore, as a proof-of-concept of clinical setting applications, a whole blood sample infected with PD-L1 (+) exosomes was analyzed, and our finding shows that this nanoarchitecture holds great promise for clinical applications

Dimension and Thickness Control Synthesis of Strongly Confined Cesium Lead Iodide Perovskites with Excellent Two-Photon Absorption Properties

Due to narrow emission peaks, high absorption cross section, and exciton binding energies, CsPbX3 perovskite-based nonlinear optical (NLO) materials are promising for next-generation quantum photonic technologies. Herein, we report dimension and thickness control synthesis of strongly confined cesium lead iodide perovskite materials, which exhibit excellent two-photon absorption (TPA) properties. Our finding reveals that the synthesis of red-emissive zero-dimensional (0D) Cs4PbI6 perovskite nanocrystals (NCs), one-dimensional (1D) CsPbI3 nanowires (NWs), and two-dimensional (2D) CsPbI3 nanoplatelets (NPLs) can be controlled by varying the temperature. Moreover, NPLs with different thicknesses can be obtained by varying the ratio of the Pb–I precursor and Cs–oleate. Furthermore, we report that the zero-dimensional (0D) Cs4PbI6 exhibits a very high two-photon absorption cross section (σ2 ∼ 12.8 × 106 GM), which is several orders of magnitude higher than the two-photon absorption cross sections reported for organic chromophores (>100 GM). Interestingly, experimentally obtained σ2 for 0D Cs4PbI6 is an order of magnitude higher than 3D CsPbI3 NCs and varies with dimensions in the following order: 0D Cs4PbI6 NCs > 1D CsPbI3 NWs > 2D CsPbI3 NPL > 3D CsPbI3. Although experimentally observed σ1 variations correlate with the volume of perovskites, σ2 does not correlate with the volume of the material. Notably, volume-normalized σ2 (VN) is highest for 2D CsPbI3 NPLs with 1.6 nm thickness, and it decreases with the increase of thickness for NPLs, which is due to the quantum confinement effect. Overall, this work provides how dimension, volume, and quantum confinement engineering can be used to design the TPA material for possible device applications

Hybrid Graphene Oxide Based Plasmonic-Magnetic Multifunctional Nanoplatform for Selective Separation and Label-Free Identification of Alzheimer’s Disease Biomarkers

Despite intense efforts, Alzheimer’s disease (AD) is one of the top public health crisis for society even at 21st century. Since presently there is no cure for AD, early diagnosis of possible AD biomarkers is crucial for the society. Driven by the need, the current manuscript reports the development of magnetic core-plasmonic shell nanoparticle attached hybrid graphene oxide based multifunctional nanoplatform which has the capability for highly selective separation of AD biomarkers from whole blood sample, followed by label-free surface enhanced Raman spectroscopy (SERS) identification in femto gram level. Experimental ELISA data show that antibody-conjugated nanoplatform has the capability to capture more than 98% AD biomarkers from the whole blood sample. Reported result shows that nanoplatform can be used for SERS “fingerprint” identification of β-amyloid and tau protein after magnetic separation even at 100 fg/mL level. Experimental results indicate that very high sensitivity achieved is mainly due to the strong plasmon-coupling which generates huge amplified electromagnetic fields at the “hot spot”. Experimental results with nontargeted HSA protein, which is one of the most abundant protein components in cerebrospinal fluid (CSF), show that multifunctional nanoplatform based AD biomarkers separation and identification is highly selective