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The present investigation sheds light on the judicious modulation of an external microenvironment to harvest optimal optical responses of organic functional molecules.

The authors thankfully acknowledge DST-FIST (SR/FST/CSI- 267/2015 (C)) and NIT Durgapur for creating and providing infrastructural facilities for research. The authors are thankful to IICB Kolkata for the HR-mass spectra analysis. SSP also acknowledge the financial support from DST SERB (EMR/2016/001230 dt.15. 03. 2017).

The present article describes the design and development of a universal device for precise and accurate distribution of time or frequency signal, i.e., one pulse per second (PPS) or 10 MHz and 5 MHz sinusoidal signal generated from an atomic clock or ensemble of atomic clocks. The frequency distribution unit provides four identical outputs of excellent stability along with suppression of all high harmonics by more than 50 dB with respect to the fundamental frequency. For time (PPS) distribution, all four outputs also provide very much similar signal as the input with excellent stability. The rising time of the output pulses is very much similar to the input pulse and stays within 3 ns.

Nowadays, most of the standards of measurement are based on fundamental constants, and among all, the SI units of time and frequency are realized with the highest precision. The SI unit of time interval, i.e. second, is realized on the basis of a hyperfine transition of ground state of 133Cesium atom in the microwave region. Atomic clocks operating at the optical frequencies have potential of providing better accuracy and higher stability than the microwave atomic clocks, and it is expected that SI second will be redefined on the basis of an optical transition. In this article, we focus on different atomic frequency standards operating in the optical domain of the spectrum by interrogating neutral atoms in optical lattice or a single ion within a radiofrequency ion trap. Recent worldwide developments along with activities at CSIR-National Physical Laboratory (CSIR-NPL) towards building optical atomic clock or optical frequency standard have also been presented.

The authors gratefully acknowledge the financial support from DST-FIST (SR/FST/CSI-267/2015(C) dt. 13. 07. 2016) for providing the infrastructural facility in the department. TM acknowledges the financial assistance from NIT Durgapur. SSP also acknowledge the financial support from DST-SERB (EMR/2016/001230 dt.15. 03. 2017). IICB, Kolkata, India for the HR-MS analysis and IBS, Daejeon, Republic of Korea for the 1H NMR spectral analysis are sincerely acknowledged.

The spread of novel coronavirus strain, Severe Acute Respiratory Syndrome 2 (SARS-CoV-2) causes Coronavirus disease (COVID-19) has now spread worldwide and effecting the entire human race. The viral genetic material is transcripted and replicated by 3 C-like protease, as a result, it is an important drug target for COVID-19. Hydroxychloroquine (HCQ) report promising results against this drug target so, we perform molecular docking followed by MD-simulation studies of HCQ and modelled some ligand (Mod-I and Mod-II) molecules with SARS-CoV-2-main protease which reveals the structural organization of the active site residues and presence of a conserve water-mediated catalytic triad that helps in the recognition of Mod-I/II ligand molecules. The study may be helpful to gain a detailed structural insight on the presence of water-mediated catalytic triad which could be useful for inhibitor modelling. Communicated by Ramaswamy H. Sarma

The efficient dispersion of carbon nanotubes in a given polymer matrix remains an open challenge. Unless addressed, the full potential of carbon nanotubes towards influencing electronic properties of a composite is far from being well understood. Although several reports are available in an open forum that addresses this challenge using various strategies, a mechanistic insight is still lacking. Herein, we have conjugated different electron-rich species with multi-walled carbon nanotubes. We systematically studied their properties by fluorescence lifetime measurements using time-correlated single-photon counting and by density functional theory. Although such conjugations vary with the electronic structure of the electron-rich species, theoretical and computational modeling sheds more light on the actual orientation of such conjugation. Taken together, the fluorescence lifetime and the type of conjugation allowed us to gain mechanistic insight into this conjugation, which further influenced several key properties of the composites. Herein, we attempted to understand these factors influencing the electrical conductivity, and electromagnetic (EM) shielding efficiency in the composite. With the addition of aminoanthracene, which established a T-shaped conjugation with multiwall carbon nanotubes (2 wt%), a remarkable -25 dB shielding effectiveness was achieved with 87% absorption for a shielding material of just 1 mm thick. The actual shielding mechanism, effect of the electronic structure, and the co-relation with the fluorescence lifetime opens new avenues in designing composite-based EM shielding materials.

Lightweight and easy to fabricate and integrate microwave absorbers are in great demand both in commercial space as well as in stealth applications given the surge in the use of wireless communication. In the past decade, research on designing polymer nanocomposite based microwave absorbers containing magnetic and conducting nanoparticles has swollen significantly; however, a clear mechanistic insight on the usage of semiconductors is far away. Herein, the potential of ``wool-ball''-like hollow semiconductor (CuS, copper sulfide) structures is explored for microwave absorption, and a mechanistic insight is proposed based on the experimental evidence. The facile synthesis approach, unique morphological structure, and optical properties make this semiconductor (CuS) quite attractive for the proposed application. In addition, the systematic analysis reveals that this material has the potential to replace the conventional conducting or magnetic nanoparticles, due to its favorable skin depth and microwave attenuation capability through dielectric heating and polarization loss. Polyvinylidene fluoride (PVDF) composites containing hollow CuS structures exhibited shielding effectiveness of 44 dB at 18 GHz, of which 86% of the incident radiation was attenuated by absorption. Further, thermal dissipation ability of this composite and its correlation with real-time microwave exposure through time-temperature response have offered new avenues in the design of microwave absorbers.

The manuscript deals with the sorption of Am(III) and Eu(III) from pH medium using chitosan functionalized with dendrimer like polyamidoamine (PAMAM) polymers up to third generation. The PAMAM polymers were introduced into chitosan by two step processes and were characterized by various instrumental techniques like FTIR, XRD, TG-DTA. The sorption process was highly pH dependent for both Am(III) and Eu(III) with increasing trend for higher pH of the solution. Kinetics of equilibration was found to be fast with equilibrium attained in 10 min for both the metal ions. Pseudo 2nd order kinetics mechanism was found to be followed for both Am(III) and Eu(III). The sorption process of Eu(III) was found to fit the Langmuir isotherm model with maximum sorption capacity of 6.01 mg/g. There was no effect on the generation of PAMAM Dendron on the efficiency, kinetics or sorption capacity for Am(III) as well as Eu(III). The synthesized different generation of PAMAM functionalized chitosan is a promising material for removal of actinides and lanthanides from waste water solution.

Precise transfer of time and frequency signals over long distances as well as clock synchronization to an ultra-stable reference are very crucial for many of the technological applications as well as for advanced scientific research. These reinforces a wide range of applications such as navigation, power grid management, mobile communication, and so on. In order to compare the performances of two highly stable and accurate atomic clocks, it is desirable that the link between the two clocks, that is, the transmission link has higher level of stability than those clocks. This article describes establishment of an ultra-stable optical fiber link employing White Rabbit network for transfer of time and frequency signals and also for comparing performance of atomic clocks. Utilizing this link, time signals have been transferred within an uncertainty of ±130 ps at ambient temperature (30°C–40°C) and the instability of the link in terms of modified Allan-deviation reaches to ∼10 −16 within one day of integration time.

Thyroid hormone receptor (THR) belongs to the nuclear receptor (NR) superfamily that is activated by binding of appropriate ligand molecules (thyroid hormones). These receptors directly bind to specific DNA sequences for gene expression, which is essential for metabolism, homeostasis, and the development of organisms, making it an important drug target. Extensive MD-simulation studies of triiodothyronine (T3) docked modeled rnTHRβ1 structures have indicated the presence of twelve conserved water molecules at the DNA-DBD (DNA binding domain) interface. The W1-W5 water centers have been involved in the recognition between the A-chain of DBD to C-chain of DNA, W6 and W7 mediated the interaction between A-chain of DBD and D-chain of DNA, W8 and W9 recognized the B-chain of DBD and C-chain of DNA, and W9-W12 centers conjugated the residues of B-chain of DBD to D-chain of DNA through hydrogen bonds. The conformation flexibility of Phe272 and Met313 residues in the absence of T3 at the LBD (ligand-binding domain) region have been observed and reported.

An increase in news articles on various communication platforms or social media has resulted in higher possibilities of spread of non-factual or fake information. The overall volume and veracity of news makes it even more impossible to manually fact check each data and label them as true or false. Under such circumstances, we propose a belief index generator model that quantifies the belief to be associated with any random information making use of text analytic proximity measures. In the initial feature engineering, we use a modified TF-IDF algorithm. Post generation of word embeddings, various distance measures have been proposed and compared as possible belief scores. The analysis has been carried out using 50K research articles on CoVid-19 to validate truths and The CoronaVirusFacts/DatosCoronaVirus Alliance Database to validate falsities in random CoVid related information.

An increase in the scientific literature related to COVID19 makes searching for scientific information a challenging task. In this paper, we present the implementation of a semantic search engine targeted at COVID19 research articles. The algorithm uses a modified Term Frequency-Inverse Document Frequency (TFIDF) features and cosine similarity with ontology maps for semantic search. The implementation includes sentiment analysis, keyword extraction, keyword-based search, phrase extraction, textual belief indication, and text summary. The system is lightweight and can be deployed as a standalone system on mobile devices. The analysis reported in the work is based on data from 50k research articles related to COVID19 research. The tool also assists the researchers to upload their own text or documents for performing analysis. The comparisons with state of the art algorithms such as BERT and Word2Vec indicate improved performance.

Precise time and frequency transfer as well as time synchronization among clocks have immense applications in different advanced technologies along with strategic applications. White Rabbit time synchronization protocol is one of the advanced technique and being utilized for precise time and frequency transfer in a large network. The present work describes establishment of a precise and stable optical fibre link for accurate time and frequency transfer utilizing White Rabbit Network. The link has been utilized for transferring time from an atomic clock in order to compare its performance with respect to another reference clock. The time deviation between the two clocks have been recorded over a long period of time and finally the fractional frequency offset between the two clocks has been derived.

We report an easy to construct imaging system that can resolve particles separated by $$\ge $$ ≥ 0.68 $$\upmu $$ μ m with minimum aberrations. Its first photon collecting lens is placed at a distance of 31.6 mm giving wide optical access. The microscope has a Numerical Aperture (NA) of 0.33, which is able to collect signal over 0.36 sr. The diffraction limited objective and magnifier recollects 77% photons into the central disc of the image with a transverse spherical aberration of 0.05 mm and magnification upto 238. The system has a depth of field of 142 $$\upmu $$ μ m and a field of view of 56 $$\upmu $$ μ m which images a large ensemble of atoms. The imaging system gives a diffraction limited performance over visible to near-infrared wavelengths on optimization of the working distance and the distance between the objective and magnifier.

Solar cookers working at intermediate temperature (120–240 ˚C) promise faster propagation of solar cooking technology as they offer a range of cooking options with reduced cooking time. As the thermal losses in such cases would be relatively high, it is pertinent to develop an appropriate rating technique. This paper attempts to identify and investigate the suitable test loads that enable the selection/rating of different designs of solar cookers at intermediate temperatures. Thus, two different working fluids have been used as the tests loads. Two different designs of solar cookers have been tested to serve the purpose using Cooker Opto-Thermal Ratio (COR) as a thermal performance parameter (TPP). The experimental results show that the use of proposed test loads yields approximately identical value of TPP for a specified design of solar cooker at intermediate temperature and enables its rating/grading at such temperatures. The impact of design change at an intermediate temperature on the TPP has been assessed by changing the radiative characteristics of the cooking pot surface to validate the proposal. It is observed that in the case of concentrating solar cooker the design change has a large impact on the TPP value and accordingly the maximum achievable cooking temperature and reference time show substantial improvement. However, in a box type cooker, the impact of design change is seen to be insignificant.

A surge in the usage of electronic devices has led to a new kind of problem; electromagnetic (EM) interference. In a quest toward providing effective shielding, which offers design flexibility, lightweight, and ease to integrate and embed, the right combination of materials needs to be synthesized and dispersed in a polymer matrix to design composites that can shield EM radiation. However, selection of nanoparticles from a vast library is quite challenging and, hence, this study attempts to provide a physical insight into the mechanism of shielding in polymer nanocomposites containing a conducting phase (here multi-walled carbon nanotubes, MWCNTs) and a magnetic phase here inverse-spinel ferrites, MFe2O4 (M = Fe, Co, Ni)]. We adopted a biphasic co-continuous blend (consisting of polycarbonate and polyvinylidene fluoride) as the matrix to incorporate the conducting and the magnetic phases. MWENTs, which offer interconnected conductive fence, and ferrites, which provide magnetic dipoles that couple with incoming EM radiation, can absorb the incoming EM radiation. The detailed mechanistic insight regarding absorption of EM radiation reveals that high saturation magnetization, high consolidated loss, better impedance matching, higher attenuation constant, high hysteresis loss, and comparable eddy current loss help Fe3O4, compared to the other ferrites employed here, to effectively shield the EM wave in the X and Ku band frequency through absorption. In addition, better impedance matching, low skin depth, and enhanced dielectric and/or interfacial polarization losses because of pi-electrons in MWCNTs suggest a synergistic effect from both the phases. As a result, -31 dB shielding effectiveness is observed in the case of Fe2O4 and MWCNTs, which is 19% higher when compared with CoFe2O4 + MWCNT-containing blends and 24% higher when compared with NiFe2O4 + MWCNT-containing blends. Interestingly, when the nanoparticles are forced to localize in different components of the blends, the overall shielding efficiency enhances further because of their higher consolidated loss parameters. Hence, the mechanistic insight provided in this paper will help guide researchers working in this field from both academic and industry perspectives.

A fluorescent, Hg2+ selective sensor, based on a Rhodamine 6G and methionine conjugate (RGM) has been devised and synthesized. The compound was well characterized by analytical techniques like 1H NMR, ESI–MS, FTIR, UV–vis absorption and fluorescence spectroscopy. The spectroscopic studies revealed that RGM displays a high selectivity and sensitivity towards Hg2+ in presence of several other interfering metal ions in Tris-HCl buffer (10 mM, pH 7.04) containing CH3CN/H2O (1:1, v/v) by forming a 1:1 complex with Hg2+. The complexation of the probe RGM with Hg2+ was also confirmed by ESI–MS and FTIR spectra. The detection limit of the probe RGM for Hg2+ was found to be 2.63 × 10−8 M. The ligand RGM and RGM-Hg2+ complex structures have been also established through theoretical studies. Moreover, the RGM-Hg2+ complex was reversible in the presence of sulphide anions and thus RGM-Hg2+ complex could also be used as an efficient sensor for S2− ions. The probe RGM was successfully applied for the detection of Hg2+ in water samples, biological cells as well as in strip test.

A novel ligand N, N, N’, N’ tetra-isobutyl pyridine diglycolamide (PDGA) was synthesized and tested for extraction of actinides and fission products present in high level liquid waste (HLLW). The ligand was studied in presence of two different diluents- nitrobenzene (NB), a molecular diluent and 3-methyl-1-octyl immidazolium bis[(trifluoromethyl)sulfonyl] imide, an Ionic Liquid (IL). Unusual selectivity towards tetravalent plutonium over minor actinides and alkali & alkaline metal ions present in nuclear waste was showed by PDGA in presence of NB as diluent. The trend in kinetics of extraction as well as dependency of DPu(IV) values with nitric acid concentration was found to be different for two diluents studied. Mechanism of extraction was also varied for the two diluents studied. It followed solvation mechanism for NB whereas for IL it was a combination of solvation and ion-exchange mechanism. The calculated Gibbs free energy of extraction, ΔGext for Pu(IV) using density functional theory was found to be higher than that of other competitive metal ions corroborating the results from solvent extraction experiment. Further, ΔGext was found to be highly negative for metal and ionic liquid cations thus complimenting the experimental findings of ion exchange mechanism for a metal cation with cation of the ionic liquid.

Removal of actinides (trivalent, tetravalent and hexavalent) from nitric acid medium was studied using solid-liquid extraction technique employing polymeric encapsulated beads (PEBs) using an indigenously synthesized, unexplored novel monoamide, N,N′-bis(2-ethyl hexyl) α-hydroxy acetamide (BEHGA). The PEBs were synthesized by phase inversion technique. The structure and morphology of the synthesized PEBs were evaluated by employing various characterization techniques like FT-IR, TGA and SEM. The well characterized PEBs were studied for its Am(III), Pu(IV) and U(VI) sorption behavior from nitric acid medium. Kinetics studies showed that the sorption is fast with equilibrium being reached within 60 min of equilibration. The sorption mechanism follows pseudo-second-order mechanism with intraparticle diffusion playing an important role. Langmuir isotherm model was found to best describe the sorption isotherm. The maximum Am(III) sorption capacity of the PEBs was found to be 8.45 mg/g (experimental) and 8.43 mg/g (Langmuir). Back extraction was possible using 0.5 M HNO3. Stability of the PEBs was found to be quite good with no significant structural deformation or leaching out of the extractant in 4.0 M HNO3 solution for at least up to 8 days.

An unexplored novel monoamide N,N′-bis(2-ethyl hexyl) α-hydroxy acetamide (BEHGA) was used as a carrier for transport of Am(III), Eu(III), Pu(IV/VI) and U(VI) from HNO3 medium across a supported liquid membrane (SLM). Various parameters were investigated to obtain the optimum transport conditions. Transport rates followed the trend Pu(IV)>Am(III)≥Eu(III)>U(VI)> Pu(VI). The effects of macro concentrations of U(VI) and Nd(III) on the transport rate of Am(III) were studied. The diffusion coefficient value for the Am(III)-BEHGA system in HNO3 medium was found to be ~1.8×10−6 cm2/s. The standard deviation of the results obtained from transport experiments by this extractant was found to be ±5%. The membrane was found to be highly selective for actinides and lanthanides with respect to different fission products.

A new simple 3-in-1 multi-response thiosemicarbazone-based chemosensor has been synthesized and characterized. The probe not only exhibited high sensitivity towards the most familiar and abundant group 12 metal ions, viz., Zn2+, Cd2+ and Hg2+, in MeCN–H2O (1 : 1, v/v) medium but also can efficiently distinguish them through significant changes in their absorption and emission spectral behavior. The selectivity response was found to follow the order Hg2+, Cd2+, Zn2+ due to the different degrees of stability of their respective complexes, which was further established by TDDFT calculations and interference studies. The binding affinities of the probe towards these metal ions were investigated by absorption, fluorescence emission, fluorescence lifetime, mass spectral and 1H NMR spectral measurements. The effects of solvent polarity on the probe molecule were also examined. Due to the observation of different binding affinities and the ensuing significant changes in absorbance at different wavelengths by a combination of different inputs, L can be judiciously applied for the construction of some basic logic gates (AND, OR, NOT, IMPLICATION and INHIBIT).

Regardless of its location, our electronic equipment does not always escape the threats of electromagnetic interference (EMI). Unrestrained radio and microwave radiation from communication devices, broadcasting stations, power lines and other electric equipment constantly bombards us and our precise circuitry equipment. Although its effects on human beings have not yet been directly demonstrated, our electronic gadgets are not that fortunate. A plethora of research work has already been published in the search for a perfect shielding material. Studies in the last decade reveal that dielectric ceramics, magnetic oxides/ferrites/particles, semiconductors, metal particles/foams, intrinsically conducting polymers, conducting carbon black/fibers/nanotubes and other carbon derivatives such as graphene etc. have been widely researched. The particles are either embedded in a wax medium or in a thermoplastic matrix to design an effective shield. To this end, polymer-based nanocomposites have been much discussed owing to their technology-matching properties, light weight, ease of fabrication and adaption, lack of corrosion, and design flexibility. However, the high dosage of nanofillers needed to meet the requirements of an effective shield mars their utility in many respects. Although bi-phasic polymer blends have been researched from different perspectives, utilizing them as a template for microwave shielding is currently drawing enormous interest compared with single-polymer-based nanocomposites. This review highlights the stepwise advancement of bi-phasic polymer blends towards EMI shielding applications. We in this manner endeavor to provide a necessary overview and point out the direction in which future research will keep on thriving as this new class of material emerges as an effective EMI shield.

An efficient and highly selective pyrene-thiophene conjugate has been reported as a dual sensor for Hg2+ and cysteamine (an important drug for genetic disorder). The sensor displays a turn-on fluorescence response towards Hg2+ in a 2:1 stoichiometric ratio via excimer formation with a detection limit as low as of 30.6 nM. The excimer emission upon binding with Hg2+ has been rationalized by experimental as well as theoritical studies. Moreover, the [probe-Hg2+] adduct functions as an efficient sensor for cysteamine. This sensing process happens via the extraction of Hg2+ from the adduct. In this paper, change in emission properties of the receptor with varying pH and water content has also been explained. The sensing abilities of the sensor were examined in real water sample analysis. Therefore, the sensor can be used as an efficient and reusable fluorescent sensor for recognition of Hg2+ in water.

Considerable attention has been given in recent years towards the development of electromagnetic interference (EMI) shielding materials. In spite of the fact that leading polymer composites containing different magnetic and dielectric nanofillers have been used broadly, nevertheless, the impact of inorganic semiconducting nanomaterials has not been utilized fully. Herein, we have designed hollow ZnS nanospheres doped reduced graphene oxide sheets (rGO) via template-free, one-pot hydrothermal synthesis process and fabricated nanocomposites with poly(vinylidene fluoride), PVDF as matrix. Three dimensional conducting network of rGO sheets along with high interacting surface area with heterogeneous dielectrics led to a very high total shielding effectiveness (-40 dB) with 93% absorption. The underlying mechanism, supported by skin-depth estimation and attenuation constant, is discussed in detail. This study opens new avenues in the field of EMI shielding materials as inorganic semiconductors show promising results in contrast to traditional materials involving conducting, dielectric and magnetic nanoparticles embedded polymer nanocomposites.

Supplying high voltage radio frequency (RF) is a critical part of ion trapping system due to impedance mismatching between RF source and the ion trap. A helical resonator has been constructed in order to deliver narrow bandwidth and high voltage RF to the ion trap for stable confinement of ions. The performances of the helical resonator have been studied for different capacitive load of the ion trap. Both the resonant frequency and quality factor of the resonator show strong dependence on external capacitive loads.

The present article describes an experimental study on precise and accurate time transfer through an optical fibre link for in house dissemination of time from an ultra-stable reference clock. The link consists of couple of single mode optical fibres and a White Rabbit (WR) link, using commercially available White Rabbit equipment along with necessary devices and software. We demonstrate time transfer accuracy remains well within 50 ps with respect to a primary clock over a very long period of time and the achieved link stability is about 10-16 at 2000 sec integration time.

Time is one of the seven base physical quantities in the SI system. In the modern world, time not only forms an essential part of day-to-day activities, but many sectorial applications related to navigation, telecommunications, and internet, power grid, banking, digital governance, transport, finance, defense, upcoming technologies of 5G, artificial intelligence, and internet of things rely on time synchronization with second to nanosecond accuracy level. Any level of time synchronization is a continuous process and requires a common national reference time that is part of the unbroken chain of international SI traceability. In many developed nations, the National Measurement Institute (NMI) provides such a common national reference time. CSIR-NPL, the NMI of India, realizes the Indian Standard Time (IST) with a timescale system consisting of bank of atomic clocks and other precision measurement instruments. Highly precise satellite links are used to keep IST traceable to UTC (coordinated universal time) within 3 ns uncertainty. Over the years, CSIR-NPL has gained knowledge and knowhow to disseminate time with various time transfer technologies. Currently, it possesses eleven calibration and measurement capabilities related to time and frequency parameters, at par with international standards. In addition, rigorous R&D activities are pursued on time transfer techniques and advanced atomic clocks like Cesium fountain and single ion trap based optical clock for more accurate and highly stable measurements of time and frequency. Metrological services in time and frequency domain viz. calibration, traceability, training, and indigenously developed products are provided to various aforementioned sectors and industries. For Pan-India time synchronization, two national metrological programs are being carried out to provide IST traceability to ISRO’s NavIC (Navigation with Indian Constellation) system and secondary timing centers at five locations for the ministry of consumer affairs (MoCA).

To minimize electromagnetic (EM) pollution, two key parameters, namely, intrinsic wave impedance matching and intense absorption of incoming EM radiation, must satisfy the utmost requirements. To target these requirements, soft conducting composites consisting of binary blends of polycarbonate (PC) and poly(vinylidene fluoride) (PVDF) were designed with doped multiwalled carbon nanotubes (MWCNTs) and a three-dimensional cross-linked graphene oxide (GO) framework doped with ferrite nanoparticles. The doping of alpha-MnO2 onto the MWCNTs ensured intrinsic wave impedance matching in addition to providing conducting pathways, and the ferrite-doped cross-linked GO facilitated the enhanced attenuation of the incoming EM radiation. This unique combination of magnetodielectric coupling led to a very high electromagnetic shielding efficiency (SE) of -37 dB at 18 GHz, dominated by absorption-driven shielding. The promising results from the composites further motivated us to rationally stack individual composites into a multilayer architecture following an absorption-multiple reflection-absorption pathway. This resulted in an impressive SE of -57 dB for a thin shield of 0.9-mm thickness. Such a high SE indicates >99.999% attenuation of the incoming EM radiation, which, together with the improvement in structural properties, validates the potential of these materials in terms of applications in cost-effective and tunable solutions.

Functional nanomaterial embedded lightweight polymer composites have drawn considerable attention across wide ranges of industrial applications. In addition to telecommunication and aerospace utilities, microwave absorbing materials must possess interesting properties that ensure excellent performance, from mechanical features to functionalities. Although conducting polymer composites containing magnetic nanofillers have been utilised widely, choosing the fillers from the library of nanoparticles and their effective dispersion inside the matrix may limit their usage in terms of performance, stability and durability. In order to overcome this bottleneck, herein we explored a facile bottom-up synthetic procedure to fabricate different shapes (spherical, cubic, cluster and flower, for example) and size-controlled Fe3O4 nanoparticles, and showed the effect of shape anisotropy and size on the above properties in a model polycarbonate (PC)/polyvinylidene difluoride (PVDF) blend with multiwalled carbon nanotubes as conducting nanofillers. The superior performance in terms of microwave attenuation and mechanical properties was reported for spherically shaped Fe3O4 nanomaterials. The excellent dispersibility of small-sized nanospheres was instrumental in the improved consolidated loss tangent values, attenuation constant, and impedance matching and skin depth, synergistically resulting in a shielding efficiency of −38 dB at 18 GHz.

A novel fluorophore–spacer–receptor has been designed with hydrazono methyl phenol as the receptor, anthracene as the fluorophore and imine (CN) groups as the spacer. This newly designed fluorophoric system has a receptor that can bind with ferrites and a fluorophore core that can conjugate non-covalently with multiwalled carbon nanotubes (MWNTs) via π–π conjugation. The hybrid nanoparticles were thoroughly characterized using Raman, UV-vis and fluorescence spectroscopy. This unique hybrid is further explored as a novel material to screen electromagnetic (EM) radiation. By precisely localizing these hybrids in a given phase of an immiscible co-continuous blend, unique microstructures can be constructed. Herein, blends of polyvinylidene fluoride (PVDF) and polycarbonate (PC) were chosen as a model system. The hybrid nanoparticles were selectively localized in the PVDF phase owing to its higher polarity and were systematically characterized by electron microscopic and solution–dissolution techniques. The hybrid nanoparticles that were designed to shield from the incident EM radiation resulted in >99.99% attenuation, dominated mostly by absorption. This non-covalent approach of conjugating MWNTs with ferrites, aided by the fluorophoric system, was noted to be a more effective way to improve the properties (both bulk electrical conductivity and structural) than direct physical mixing/covalent conjugation approaches. In order to further enhance the shielding effectiveness (SE), a layer-by-layer architecture was constructed essentially with outer layers containing PC/PVDF blends with a MWNT–ferrite hybrid and the inner layers consisting of PC/PVDF blends with only MWNTs. An ultra-thin shield of 0.90 mm showed >99.9999% attenuation suggesting new pathways for designing lightweight, flexible EMI shielding materials.

The fabrication of thin multilayer polymer nanocomposite films and their judicious arrangement in a sandwich structure to attenuate incoming electromagnetic (EM) radiation, mostly by absorption, is discussed herein. Two key properties (reasonably high conductivity, with high dielectric loss and magnetic permeability) were targeted here by using multiwall nanotubes (MWCNTs) and BaTiO3/Fe3O4 (BT/Fe) co-doped graphene oxide (GO) sheets to design soft functional nanocomposites using bi-component blends of PC (polycarbonate) and PVDF (polyvinylidene fluoride). High dielectric loss and magnetic permeability were achieved by uniformly distributing BT and Fe nanoparticles on the huge specific surface area provided by the GO sheets. The MWCNTs were non-covalently modified to exfoliate the nanotubes and to get a well-connected structure of the blend components. The MWCNTs were thoroughly characterized by TEM, UV-vis, fluorescence emission, Raman and TGA. This surface modification of the MWCNTs also helps with their specific localization in the continuous bi-component blends. BT and Fe were co-doped onto the GO sheets by a well-designed step-by-step synthesis protocol, and the product can facilitate the absorption of incoming EM radiation. This hybrid structure was thoroughly characterized by various microscopic and spectroscopic techniques. By following a sequential mixing protocol, the BT/Fe co-doped GO sheets can be specifically localized in the PC components of the blends while the MWCNTs localize in the PVDF phase through a process driven by thermodynamics. This provides excellent heterogeneous boundaries with multiple scattering within the engineered nanostructures, in addition to retaining the conducting network and the associated dielectric loss properties. The resultant local field variation of such boundaries and the presence of highly lossy materials readily enhance the EM attenuation coefficient. The bulk compositions exhibited a high shielding effectiveness (SE) of −35 dB at 18 GHz (>85% absorption), and when rationally stacked into a multilayer architecture with absorption–multiple reflection–absorption pathways, the SE was further enhanced to −46 dB for a thin shield of 0.9 mm thickness. Such a high SE indicates >99.99% attenuation of the incoming EM radiation. This new-generation EM suppressor, distinguished by its multifunctionality and tunable dielectric and magnetic properties, hence offers an amendable, cost-effective replacement to existing solutions.

Steady state fluorescence spectroscopic technique has been used to investigate the aggregation of coal derived asphaltene (CDA) sourced from Lodna Coke Plant situated at Dhanbad, India. The emission spectra of CDA provide information regarding the various stages of onset of aggregation in carbon tetrachloride medium. Almost similar results have also been inferred from the analysis of corresponding excitation spectra. It has been observed that the onset of aggregation of CDA occurs at concentration beyond a concentration of 10 mg L−1. Studies indicate the formation of a trimer at this concentration range. The association constant (K) for the trimer formation has also been evaluated from the spectroscopic data.

Both petroleum and coal derived asphaltene finds important place on the present research areas of hydrocarbon based liquid and solid fuels. It has earned a name of ‘unwanted’ fame for its deleterious impacts arising mainly due to its self aggregational phenomenon. Over the period of time the asphaltene aggregation has been seriously investigated worldwide even at the molecular scale. Besides several methods, the spectroscopic findings (UV Vis and Fluorescence), in this regard, contribute to substantial meaningful data. The major spectroscopic researches on the aggregation of asphaltene over the last ten years have been reviewed in this present study. A brief discussion on the asphaltene molecular structure and molecular weight also comes as a prelude. Asphaltenes derived from both petroleum and coal have been considered.

The multifaceted photodynamics of a simple azine based organic functional molecule namely 2-((Z)-((E)-(pyren-1-ylmethylene)hydrazono)methyl)quinolin-8-ol (PHQ) emphasizing its brilliant fluorescence emission redemption properties in aggregation state (AIEE) have been primarily explored through absorption and steady state emission techniques. The governing role of photo-induced electron transfer (PET) rates and active intramolecular motions of non-interacting PHQ monomers at lower water fraction comprising mixed solvent systems have been identified to be the prime reasons for non-radiative annihilation of photoexcited states. The transition from weakly emissive to highly emissive state has been substantiated through elaborate study using time-resolved photoluminescence (TRPL), fluorescence quantum yield and variation of external control experiments. In the current study, the increased rotational relaxation time of aggregated hydrosol, responsible for AIEE, is investigated using time-resolved anisotropy measurement (TRAM) of different PHQ microenvironments, which is unprecedented to the best of our knowledge in AIEE research. Interestingly, the high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) image shows one dimensionally grown molecular entity of a single nano-sheet like structure of PHQ, which is a unique observation. The average particle size of PHQ aggregates is also increased from 84.5 nm to 814 nm corresponding to 10% and 90% fw (water volume %) system respectively. The energy-dispersive X-ray spectroscopy (EDX) has also been employed, for the first time in AIEE research, which reveals a gradual increase in the amount of carbon within the aggregated microstructure with addition of water. The present molecular system PHQ, being a molecular rotor system, provides future prospect for probing local microenvironmental viscosities within biological systems.