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Monolayer MoSe2 flakes with varying shapes, including sharp triangle, truncated triangle, hexagon, and rough edge circle are synthesized using APCVD method. The lattice and quasiparticle dynamics are examined under different growth conditions.

In the field of optoelectronics, all-inorganic CsPbBr3 perovskite nanocrystals (PNCs) have gained significant interest on account of their superb processability and ultra-high stability among all the counterparts. In this study, we conducted an in-depth analysis of CsPbBr3 PNCs using joint transient optical spectroscopies (time-resolved photoluminescence and ultrafast transient absorption) in a very comprehensive manner. In order to understand the in-depth analysis of excited-state kinetics, the transient absorption spectroscopy has been performed. The structure of interest of CsPbBr3 PNCs was subjected to the rates of the radiation energy of 0.10 mW (κr/κnr = ∼0.62) and 0.30 mW (κr/κnr = ∼0.64). With the rate of radiation energy 0.30 mW, it was observed that there was a significant increase in hot carrier relaxation together with high radiative recombination, resulting in a decrease in charge trappings. Herein, we demonstrate that the tuning of the rate of radiation energies helps to understand the charge-carrier kinetics of CsPbBr3 PNCs, which would thus improve the manufacturing of efficient photovoltaic devices.

Heteroatom doping in graphene is now a practiced way to alter its electronic and chemical properties to design a highly-efficient gas sensor for practical applications. In this series, here we propose boron-doped few-layer graphene for enhanced ammonia gas sensing, which could be a potential candidate for designing a sensing device. A facile approach has been used for synthesizing boron-doped few-layer graphene (BFLGr) by using a low-pressure chemical vapor deposition (LPCVD) method. Further, Raman spectroscopy has been performed to confirm the formation of graphene and XPS and FESEM characterization were carried out to validate the boron doping in the graphene lattice. To fabricate the gas sensing device, an Si/SiO2 substrate with gold patterned electrodes was used. More remarkably, the BFLGr-based sensor exhibits an extremely quick response for ammonia gas sensing with fast recovery at ambient conditions. Hence, the obtained results for the BFLGr-based gas sensor provide a new platform to design next-generation lightweight and fast gas sensing devices.

The quality of as-synthesized monolayers plays a significant role in atomically thin semiconducting transition metal dichalcogenides (TMDCs) to determine the electronic and optical properties. For designing optoelectronic devices, exploring the effect of processing parameters on optical properties is a prerequisite. In this view, we present the influence of processing parameters on the lattice and quasiparticle dynamics of monolayer MoSe

In the field of optoelectronics, all-inorganic CsPbBr

Rare-earth free and biocompatible two dimensional carbon based boron oxynitride (2D BCNO) nanophosphors were synthesized using facile auto-combustion of inexpensive compounds such as urea, boric acid and polyethylene glycol at ambient atmosphere and relatively low temperatures. The surface morphology and microstructure images indicate that the nanophosphor has 2D layered structures and analogous mixed hexagonal lattices of boron nitride (BN) and graphene (C). The nanophosphor exhibits a single, distinct and broad photoluminescence emission and this emission colour can be easily tuned from violet to deep red by varying the amount of boron/carbon content. The time-resolved and photoluminescence spectroscopic results indicate that B–O act as luminescence centers, which are responsible for the tunable luminescent properties while carbon impurities induce energy levels in the band gap of 2D BCNO nanophosphors. These tunable and biocompatible luminescent nanophosphors are used for in vitro high-contrast cellular imaging of HeLa cells derived from human cervical cancer cells as well as in vivo imaging in C57BL/6J mice. Hence, these novel multi-colour emitting nanophosphors provide a paradigm shift in rare-earth free biocompatible nanoprobes for next generation high-contrast in vitro and in vivo imaging applications.

Herein, we introduce a novel strategy for the synthesis of Eu3+ doped α-sodium gadolinium fluoride (α-NaGd0.88F4:Eu0.123+) based luminomagnetic nanophosphors using a hydrothermal route. The synthesized nanophosphor has exceptional luminescent and paramagnetic properties in a single host lattice, which is highly desirable for biomedical applications. This highly luminescent nanophosphor with an average particle size ∼5 ± 3 nm enables high-contrast fluorescent imaging with decreased light scattering. In vitro cellular uptake is shown by fluorescent microscopy that envisages the characteristic hypersensitive red emission of Eu3+ doped α-sodium gadolinium fluoride centered at 608 nm (5D0–7F2) upon 465 nm excitation wavelength. No apparent cytotoxicity is observed. Furthermore, time-resolved emission spectroscopy and SQUID magnetic measurements successfully demonstrate a photoluminescence decay time of microseconds and an enhanced paramagnetic behavior, which holds promise for the application of nanophosphors in biomedical studies. Hence, the obtained results strongly suggest that this nanophosphor could be potentially used as a bimodal nanoprobe for high-contrast in vitro bioimaging of HeLa cells and external magnetic field tracking applications of luminomagnetic nanophosphors using permanent magnet.

Herein, we design and develop a field emission device utilizing highly porous carbon nanocup (CNC) films. These three-dimensional (3D) low-aspect ratio CNC structures were fabricated by a combination of anodization and chemical vapor deposition techniques. The low turn-on fields of 2.30 V μm−1 were observed to draw an emission current density of 1 μA cm−2 and a maximum emission current density of ∼1.802 mA cm−2 drawn at an applied field of ∼4.20 V μm−1. The enhanced field emission behavior observed from the CNC films is attributed to an excellent field enhancement factor of 1645. The observed field emission properties of CNC arrays are attributed to a synergistic combination of high aspect ratio, nano-sized radius of curvature, highly organized distribution of the emitters over the whole area of specimen and lower screening effect of the CNC arrays. These observations shed light on the effect of the stacking carbon layers of CNC on their electronic properties and open up possibilities to integrate new morphologies of graphitic carbon in nanotechnology applications. Thus, the low turn on field, high emission current density and better emission current stability enable CNC based future field emission applications.

A novel strategy was introduced to produce large-scale pristine MgO nanostructures as a feasible candidate for light harvesting applications. Herein, MgO nanostructures with a nanoflakes-/nanofibers-like morphology were synthesized by a co-precipitation route at different calcination temperatures ranging from 500 to 1100 °C and well characterized by several standard experimental techniques, such as XRD, FTIR, SEM, EDX, and TEM, to confirm the formation of MgO nanostructures. Undoped MgO nanostructures obtained at 1100 °C exhibited a strong photoluminescence (PL) emission spectrum at 668 nm (hypersensitive red) at 466 nm excitation wavelength. Moreover, these nanostructures also showed strong blue (477 nm) and red (668 nm) luminescence emissions simultaneously at an excitation wavelength of 317 nm. Further investigations probed by PL mapping demonstrated the homogeneous distribution of PL intensity throughout the MgO surfaces and time-resolved photoluminescence spectroscopy results of these nanostructures indicated a decay time of less than 10 ns. Thus, the facile synthesis of these luminescent undoped MgO nanostructures provides a potential platform to harvest white light generation (a combination of blue and red emissions) as well as their potential use in LED applications.

Correction for ‘Boron-doped few-layer graphene nanosheet gas sensor for enhanced ammonia sensing at room temperature’ by Shubhda Srivastava et al., RSC Adv., 2020, 10, 1007–1014. DOI: 10.1039/C9RA08707A

We have successfully synthesized rare-earth doped gadolinium molybdate Gd2(MoO4)3:Re3+ (Re3+ = Eu3+, Tb3+, Tm3+ and Er3+/Yb3+) nanophosphors for solar cell application as a broad spectral converter from the ultraviolet (UV) to the near infrared (NIR) regions in a single host lattice using a facile solid state reaction method. The gross structure, surface morphology and microstructure of these nanophosphors have been investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission/high-resolution transmission electron microscopy (TEM/HRTEM) techniques , respectively. Photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectroscopic methods have been used to explore the striking luminescence properties of the synthesized nanophosphors. The Gd2(MoO4)3:Eu3+ nanophosphor exhibits a hypersensitive red emission (616 nm) at an excitation wavelength in the range of 250–475 nm corresponding to a 5D0–7F2 transition. The Gd2(MoO4)3:Tb3+ and Gd2(MoO4)3:Tm3+ nanophosphors demonstrate a strong green emission at 541 nm and a deep blue emission at 453 nm upon an excitation wavelength of 378 nm and 266 nm, respectively. Moreover, the upconversion characteristic of the Gd2(MoO4)3:Er3+/Yb3+ nanophosphor exhibits strong green emission at 545 nm and red emission at 657 nm corresponding to 4S3/2–4I15/2 and 4F9/2–4I15/2 transitions respectively. Furthermore, the Gd2(MoO4)3:Er3+/Yb3+ upconversion nanophosphor emits in the NIR spectrum region at 994 nm upon a 980 nm excitation wavelength. Hence, the obtained PL emission results with a lifetime in milliseconds reveal that these nanophosphors could be futuristic promising broad spectral converter phosphors which may possibly integrate with the next-generation Si-solar cell to enhance the efficiency of the cell.

Here we report the microwave shielding properties of a light weight three dimensional (3D) sponge like graphene aerogel (GA) derived from graphene oxide (GO). GA is a new exotic form of graphene nanosheet, which shows improved shielding features as compared to its pristine counterpart. The structural and microstructural characteristics of this new indigenous 3D sponge like graphene aerogel architecture have been probed by XRD, Raman, SEM and TEM/HRTEM. Furthermore, the porosity of this newly synthesized structure has been investigated by the Brunauer–Emmett–Teller (BET) method, which confirms the high surface area of ∼516 m2 g−1 with an average pore diameter of ∼2.5 nm. The high surface area and better porosity improve the EMI shielding effectiveness of GA. Simultaneously, the GA nanostructure also enhances the dielectric properties which provide a better alternative for EMI shielding materials as compared to GO. This engineered GA exhibits enhanced shielding effectiveness (∼20.0 dB at 0.20 g in a frequency region of 12.4 to 18.0 GHz) as compared to the conventional GO. Thus, the result of the EMI shielding of GA offers a new ingenious nanostructure which can be used as an EMI pollutant quencher for next-generation EMI shielding devices.

Herein, we demonstrate a facile one pot synthesis of graphene nanosheets by electrochemical exfoliation of graphite. In the present study, we report a significant increase in the yield of graphene by electrolyte heating assisted electrochemical exfoliation method. The obtained results of heating assisted electrochemically exfoliated graphene (utilizing H2SO4 + KOH + DW) synthesis clearly exhibit that the yield increases ∼4.5 times i.e. from ∼17% (room temperature) to ∼77% (at 80 °C). A plausible mechanism for the enhanced yield based on lattice expansion and vibration of intercalated ions has been put forward and discussed in details. The quality of graphene was examined by Raman, XPS, FTIR, AFM, SEM, TEM/HRTEM and TGA techniques. The Raman as well as morphogenesis results confirm the quality of the graphene nanosheets. We have used this graphene as electromagnetic interference shielding material where a comparatively large quantity of graphene is required. This graphene exhibits enhanced shielding effectiveness (46 dB at 1 mm thickness of stacked graphene sheets in frequency region 12.4 to 18 GHz) as compared to conventional electromagnetic interference shielding materials, which is greater than the recommended limit (∼30 dB) for techno-commercial applications. Thus the present work is suggestive for future studies on enhancement of yield of high quality graphene by proposed method and the use of synthesized graphene in electromagnetic interference shielding and other possible applications.

Herein, a novel strategy has been proposed to fabricate graphene quantum dots (GQDs) infilled titanium dioxide (TiO2) nanotube arrays (NTAs) hybrid structure for dye degradation of methylene blue (MB) under UV light (365 nm) irradiation. GQDs are infilled inside the TiO2 NTAs (via anodic oxidation of a Ti sheet) through an impregnation method. Moreover, the morphology of the TiO2 NTAs is well maintained after filling the GQDs inside, which is favorable for mass transfer. The peak intensity of photoluminescence (PL) spectra of the GQDs infilled TiO2 NTAs catalyst is lower than that of annealed TiO2 NTAs and a strong violet UV emission is obtained at 387 nm upon 252 nm deep UV excitation. The photocatalytic activities of the TiO2 NTAs are evaluated in terms of the efficiencies of photo-decomposition and adsorption of MB in aqueous solution under UV light irradiation, after the impregnation of GQDs inside the TiO2 NTAs. The highly-efficient photocatalytic activity is attributed to the broad absorption in the visible wavelength region, large photo-induced charge separation through the transfer of photo-generated electrons from the TiO2 NTAs to GQDs, as well as the strong adsorption capacity of the GQDs to MB molecules. Thus, the GQDs infilled TiO2 NTAs could be widely used as a photocatalyst for treating organic contaminants in the field of environmental protection.

Herein, we introduce a novel strategy for the synthesis of Eu3+ doped α-sodium gadolinium fluoride (α-NaGd0.88F4:Eu0.123+) based luminomagnetic nanophosphors using hydrothermal route. The synthesized nanophosphor has exceptional luminescent and paramagnetic properties in a single host lattice, which is highly desirable for biomedical applications. This highly luminescent nanophosphor with an average particle size ∼ 5±3 nm enables high-contrast fluorescent imaging with decreased light scattering. In vitro cellular uptake is shown by fluorescent microscopy that envisages the characteristic hypersensitive red emission of Eu3+ doped α-sodium gadolinium fluoride centered at 608 nm (5D0-7F2) upon 465 nm excitation wavelength. No apparent cytotoxicity is observed. Furthermore, time- resolved emission spectroscopy and SQUID magnetic measurements successfully demonstrate a photoluminescence decay time in microseconds and enhanced paramagnetic behavior respectively, which promises the applications of nanophosphors in biomedical studies. Hence, the obtained results strongly suggest that this nanophosphor could be potentially used as a bimodal nanoprobe for high-contrast in vitro bio-imaging of HeLa cells and external magnetic field tracking applications of luminomagnetic nanophosphors using permanent magnet.