Publications by authors named "Pintu Ghosh"

The direct utilization of carbon dioxide as an ideal one-carbon source in value-added chemical synthesis has garnered significant attention from the standpoint of global sustainability. In this regard, the photo/electrochemical reduction of CO into useful fuels and chemical feedstocks could offer a great promise for the transition to a carbon-neutral economy. However, challenges in product selectivity continue to limit the practical application of these systems.

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Hypochlorite, as an important reactive oxygen species (ROS), plays a vital role in many physiological and pathological processes, but an excess concentration of hypochlorite (ClO) may become toxic to humans and cause disease. Hence, the selective and rapid detection of hypochlorite (ClO) is necessary for human safety. Here, we report a novel near-infrared (NIR) fluorescence "turn-on" and highly selective benzophenoxazinium chloride-based fluorescent probe, (benzophenoxazinium dihydroxy benzaldehyde), for hypochlorite detection.

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Article Synopsis
  • Phosgene, diphosgene, and chlorine are highly toxic choking agents that can cause serious respiratory issues, including death, leading to the development of small-molecule fluorescent probes for safe detection.
  • Two designed probes, TCAO and HMBT, were evaluated, with TCAO showing greater selectivity and sensitivity for phosgene detection due to its electron-donating group.
  • TCAO was further studied, revealing a significant increase in its quantum yield upon phosgene exposure and achieving a detection limit of 51 nm, with a user-friendly paper-strip method for onsite monitoring.
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In the current situation, peroxynitrite (ONOO) is drawing the increasing attention of researchers for its pivotal role in diverse pathological and physiological processes on grounds of robust oxidation and nitrification. Herein, we have successfully designed and synthesized a phenanthrenequinone benzyl borate-based chemosensor for fast and selective detection of ONOO. The probe itself had an orange fluorescence, which was changed to strong blue fluorescence upon the addition of ONOO, indicating the ratiometric response of the probe.

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A highly selective thiophene-thioimidazole hydrazine-based ratiometric chemodosimeter (TPBN) was designed and synthesized to detect hypochlorite (ClO). The probe showed yellow fluorescence and exhibited ultra sensitivity towards hypochlorite (detection limit 8.74 nM) through the oxidative intramolecular cyclization process to give a blue fluorescent triazole product (TPBN-P).

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Over the past few decades, the advent of C-H activation has led to a rethink among chemists about the synthetic strategies employed for multi-step transformations. Indeed, deploying innovative and masterful tricks against the numerous classical organic transformations has been the need of the hour. Despite this, the immense importance of C-H activation remains unfulfilled unless the methodology can be deployed for large-scale industrial processes and towards the concise, step-economic synthesis of prodigious natural products and pharmaceutical drugs.

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Amide bonds connect the amino acids in proteins and exist as a prevalent structural motif in biomolecules. Herein, we have exploited the concept of cross-electrophile coupling by merging the photo-redox and transition-metal catalysis to construct carbamides from superabundant (hetero)aryl halides along with commercially feasible carbamoyl chlorides. The success of this method relies on the prior formation of Ni -aryl halide intermediates, which involves in a photoexcited Ni-halide homolysis event by energy transfer from aryl bromide and single-electron transfer from aryl chloride to assist generation of the vital carbamoyl radical.

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Multispectral camouflage, especially for the infrared-microwave range, is an essential technology for the safety of facilities, vehicles, and humans. So far, it has been realized mainly by high infrared specular reflection and high microwave absorption. However, external infrared sources can expose the target through specular reflection; also, the heat production from microwave absorption can increase the infrared radiation.

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Article Synopsis
  • * A new strategy using specially designed coatings on both the inside and outside of enclosure roofs enhances thermal management, allowing for better energy exchange without compromising aesthetics.
  • * This method can reduce the power consumption of active coolers by up to 63% at a target temperature of 26°C, providing an easy way to improve energy efficiency and contribute to carbon neutrality.
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Thermal emission engineering with ability to realize spectral and spatial selection has attracted great attention in recent years. Nanophotonic control of thermal radiation has demonstrated narrowband thermal emitter but with high angle-sensitivity and diffuse thermal emitter but with low quality factor (). Here, we demonstrate a simultaneous narrowband, diffuse thermal emitter consisting of 80 nm ( View Article and Find Full Text PDF

Biocatalysis integrate microbiologists, enzymologists, and organic chemists to access the repertoire of pharmaceutical and agrochemicals with high chemoselectivity, regioselectivity, and enantioselectivity. The saturation of carbon-carbon double bonds by biocatalysts challenges the conventional chemical methodology as it bypasses the use of precious metals (in combination with chiral ligands and molecular hydrogen) or organocatalysts. In this line, Ene-reductases (ERs) from the Old Yellow Enzymes (OYEs) family are found to be a prominent asymmetric biocatalyst that is increasingly used in academia and industries towards unparalleled stereoselective trans-hydrogenations of activated C=C bonds.

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An efficient Rh(III)-catalyzed straightforward strategy is developed for the synthesis of quinoline braced cyclophane macrocycles methyl (sp) C-H functionalization. The method is mild, simple and regioselective with various ring sizes and has good functional group tolerance. The method proceeds C8-methyl metalation, metal-carbene formation and a subsequent migratory insertion.

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Control of thermal emission underpins fundamental science, as it is related to both heat and infrared electromagnetic wave transport. However, realizing nonvolatile reconfigurable thermal emission is challenging due to the inherent complexity or limitation in conventional radiative materials or structures. Here, we experimentally demonstrate a nonvolatile optically reconfigurable mid-infrared coding radiative metasurface.

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Outdoor personal thermal comfort is of substantial significance to ameliorate the health conditions of pedestrian and outdoor laborer. However, the uncontrollable sunlight, substantial radiative loss, and intense temperature fluctuations in the outdoor environment present majestic challenges to outdoor personal thermal management. Here, we report an eco-friendly passive nanostructured textile which harvests energy from the sun and the outer space for optional localized heating and cooling.

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Metal nanomaterials have been widely used to generate photoacoustic (PA) signals because of their high optical absorption characteristics. However, the PA conversion efficiency of metal nanomaterials is limited by the single-wavelength absorption at the resonant peak. To mitigate this issue, a three-layer ultrathin film containing a thin PDMS layer sandwiched between two ultrathin chromium films is proposed.

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Interminable surveillance and reconnaissance through various sophisticated multispectral detectors present threats to military equipment and manpower. However, a combination of detectors operating in different wavelength bands (from hundreds of nanometers to centimeters) and based on different principles raises challenges to the conventional single-band camouflage devices. In this paper, multispectral camouflage is demonstrated for the visible, mid-infrared (MIR, 3-5 and 8-14 μm), lasers (1.

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Article Synopsis
  • Artificial neural networks have significantly enhanced machine learning applications, but current electronic hardware is hitting performance limits due to slowing advancements in technology (Moore's Law).
  • The proposed solution is an optical neural network utilizing optical scattering units, which can perform deep learning tasks efficiently with high speed, low power usage, and a compact size.
  • These optical units can execute precise matrix calculations with minimal error and have demonstrated a high accuracy rate of 97.1% on the MNIST image classification dataset.
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High-temperature infrared (IR) camouflage is crucial to the effective concealment of high-temperature objects but remains a challenging issue, as the thermal radiation of an object is proportional to the fourth power of temperature (). Here, we experimentally demonstrate high-temperature IR camouflage with efficient thermal management. By combining a silica aerogel for thermal insulation and a Ge/ZnS multilayer wavelength-selective emitter for simultaneous radiative cooling (high emittance in the 5-8 μm non-atmospheric window) and IR camouflage (low emittance in the 8-14 μm atmospheric window), the surface temperature of an object is reduced from 873 to 410 K.

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Achieving light-driven motions in nonliquid environments presents formidable challenges, because microsized objects experience strong dry adhesion and intend to be stuck to contact surfaces with great tenacity. Here, in air and vacuum, we show rotary locomotion of a micrometer-sized metal plate with ~30 nm thickness, revolving around a microfiber. This motor is powered by pulsed light guided into the fiber as a coordinated consequence of an optically excited Lamb wave on the plate and favorable configuration of plate-fiber geometry.

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Camouflage technology has attracted growing interest for many thermal applications. Previous experimental demonstrations of thermal camouflage technology have not adequately explored the ability to continuously camouflage objects either at varying background temperatures or for wide observation angles. In this study, a thermal camouflage device incorporating the phase-changing material GeSbTe (GST) is experimentally demonstrated.

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A narrowband thermal emitter exhibits higher energy efficiency and sensitivity in molecule sensing and other mid-infrared (MIR) spectral range applications compared to a blackbody emitter. Most narrowband thermal emitters involving surface plasmons have a relatively low quality factor (Q-factor) and require complex fabrication processes. Here we propose a bilayer cavity-enhanced Tamm plasmon (TP) structure with a high/low refractive index bilayer sandwiched between a metal and distributed Bragg reflector (DBR) to achieve an enhanced Q-factor and maintain higher emittance over a conventional pure DBR-metal TP structure-based emitters.

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Energy-efficient nanosoldering technology for realizing connections at the nanoscale is a long-sought-after goal for constructing advanced optoelectronic nanodevices. However, the ability to achieve noncontact handling, low power consumption, and targeted nanosoldering remains a challenge. In this work, we demonstrate a method of targeted photothermal-induced nanosoldering of silver nanowires, which uses AuSn alloy nanowires as the nanosolder and a 532 nm continuous wave laser as the heat source.

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A technique to fabricate nanogaps with controllably variable gap width in silver (Ag) nanowires (NWs) by photothermal-induced stress utilizing a focused continuous-wave laser (532 nm) is presented. For the case of an Ag NW on gold thin film, a gap width starting from ∼20  nm is achieved with a critical minimum power (CMP) of about 160 mW, whereas in the case of an Ag NW placed on top of a zinc oxide NW, the attained gap width is as small as a few nm (<10  nm) with a CMP of only ∼100  mW. In both cases, the CMP is much lower as compared to the required CMP (∼280  mW) for an Ag NW placed on a bare silica substrate.

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