Sahu, Satyajit

All inorganic halide perovskites have received tremendous significance in the perovskite solar cells (PSCs) technology. The toxicity in PSCs due to Pb element concerns to the environment, thus replacement of Pb is a prerequisite in the development of PSCs. In this study, we have studied strain-induced structural and electronic properties of lead-free ASnBr3 (A = Cs, Rb, K) perovskites using density functional theory based first principles calculation. The band gap values of these perovskites are varied from 0 to 1.14 eV within the strain range of -4 to 4%.

We propose fractal information theory (FIT) to compute, and it uses a Fractal tape, wherein “every single cell of a Turing tape contains a Turing tape inside.” To use this tape, we introduce a geometric musical language (GML). This language has only one letter, a time cycle, a rhythm, a clock, or a unitary operator; on the circle perimeter, multiple singular bursts or “bings” (singularity represented as circles) are located. Time gap or “silence” between the “bings” is adjusted to hold the geometric parameters of structures such as square, triangle. Each time cycle is part of a phase space or a Bloch sphere; hence, information is now a “Bloch sphere with a clocking geometry.” Several such spheres self-assemble and expand like a balloon to store and process complex information; “bings” are singularity glue to add clocking Bloch spheres into it; this is the basic of fractal information theory (FIT). The conversion of five sensory signals into geometric shapes and rhythms like music and vice versa is called geometric musical language (GML). New information is integrated as guest into a single ever-expanding host Bloch sphere. The distinction between questions and answers disappears and replaced by “situation,” written as geometric shapes and always paired together in a time cycle, side by side or one inside another. Just like a human brain, FIT-GML hypercomputing does not require algorithm or programming, and it uses the fractal beating, i.e., geometric nesting inside a Hilbert space. FIT reduces to quantum information theory, QIT, if the clocking geometry in the Bloch sphere and virtual poles are removed and the singularity feature of a “bing” is eliminated, which makes it a classical state.

The thermoelectric materials so far discovered have shown thermoelectric behavior at relatively higher temperatures. Low temperature thermoelectric materials are the need of the hour and in this work we have studied the thermoelectric behavior of 2D monolayer of XI2 (X = Sn, Si) at relatively low temperature by using Density Functional Theory (DFT) along with the Boltzmann Transport equation. We have found high thermoelectric figure of merit (ZT) for SnI2 and SiI2 at 600 K. At room temperature the maximum ZT is 0.66 (0.35), 0.78 (0.51) for p-type (n-type) SnI2 and SiI2 respectively and at 600 K it is 0.83 for SiI2. The study of the optical properties of both the materials shows that both of them have indirect band gap with SnI2 having a band gap of 2.06 eV where as SiI2 has a band gap of 1.63 eV. Both the materials have a very high absorption coefficient in the ultraviolet (UV) region hence these materials can be used as high sensitive UV photodetectors. Thus the SnI2 and SiI2 2D monolayers can have potential application in optoelectronic as well as thermoelectric device fabrication.

In the present work, the unique negative differential resistance (NDR) and memory effect of an organic-metallic hybrid polymer based on the self-assembly of Fe(ii)-ions preceded by the synthesis of a newly designed multidentate Schiff's base ligand has been reported. The polymerization process was closely monitored in an absorbance study using a UV-vis spectrophotomer. The presence of sharp isosbestic points and saturation of absorbance at 1 : 1 ligand to metal concentration confirmed the stepwise growth of the polymer. A model monomer Fe-complex was also developed based on the model ligand, with the aim of understanding the properties of the polymer in a better way by comparative study but surprisingly both ligand and model ligand coordinate in a different fashion with the same Fe(ii)-metal ions under similar reaction conditions, though both of them have identical binding sites. It has been found that the monomer model complex is paramagnetic while the metallopolymer is diamagnetic in nature. FESEM images of thin films of the polymer revealed the presence of homogeneously distributed interparticulate mesopores which was further confirmed by surface area analysis. A long single strand of the polymer was found on the HOPG surface by AFM study. The cyclic voltammetry study indicated that both conjugated ligand and metallopolymers are electrochemically active. The bistable memory behaviour of the device fabricated on ITO has shown a negative differential resistance effect along with good RAM and ROM behaviour, showing the potential of this novel polymer as memristor.

As we bring tubulin protein molecules one by one into the vicinity, they self-assemble and entire event we capture live via quantum tunneling. We observe how these molecules form a linear chain and then chains self-assemble into 2D sheet, an essential for microtubule, -fundamental nano-tube in a cellular life form. Even without using GTP, or any chemical reaction, but applying particular ac signal using specially designed antenna around atomic sharp tip we could carry out the self-assembly, however, if there is no electromagnetic pumping, no self-assembly is observed. In order to verify this atomic scale observation, we have built an artificial cell-like environment with nano-scale engineering and repeated spontaneous growth of tubulin protein to its complex with and without electromagnetic signal. We used 64 combinations of plant, animal and fungi tubulins and several doping molecules used as drug, and repeatedly observed that the long reported common frequency region where protein folds mechanically and its structures vibrate electromagnetically. Under pumping, the growth process exhibits a unique organized behavior unprecedented otherwise. Thus, "common frequency point" is proposed as a tool to regulate protein complex related diseases in the future.

We have shown an exponential increase in the ratio of conductance in the on and off states of switching devices by controlling the surface morphology of the thin films for the device by depositing at different rotational speeds. The pinholes which are preferred topography on the surface at higher rotational speed give rise to higher on–off ratio of current from the devices fabricated at the speed. The lower rotational speed contributes to higher thickness of the film and hence no switching. For thicker films, the domain is formed due to phase segregation between the two components in the film, which also indicates that the film is far from thermal equilibrium. At higher speed, there is very little scope of segregation when the film is drying up. Hence, there are only few pinholes on the surface of the film which are shallow. So, the filamentary mechanism of switching in memory devices can be firmly established by varying the speed of thin film deposition which leads to phase segregation of the materials. Thus, the formation of filament can be regulated by controlling the thickness and the surface morphology.

A substantial ion flow in a normally wet protein masks any other forms of signal transmission. We use hysteresis and linear conduction (both are artifacts) as a marker to precisely wet a protein, which restricts the ionic conduction (hysteresis disappears), and at the same time, it is not denatured (quantized conductance and Raman spectra are intact). Pure electric visualization of proteins at work by eliminating the screening of ions, electrons, would change the way we study biology. Here we discuss the technical challenges resolved for imaging a protein or live cell using nonlinear dielectric response (spatial distribution of conductance, capacitance and phase, GCP trio). We electromagnetically triggered electrical, mechanical, thermal and ionic resonant vibrations in a protein. During resonant oscillations, we imaged the protein using resonant scanning tunneling microscopy of biomaterials (Brestum) and during ionic firing we imaged live what happens inside an axon core of a neuron by using our atomic scale scanning dielectric microscopy (Asadim). Both Asadim and Brestum are housed in a homebuilt scanning tunneling microscope (bio-STM) and a special micro-grid developed by us (patent JP-5187804) for fractal supercomputing. We found the trick to turn a membrane transparent and see inside without making any physical contact. We image live that a protein molecule adopts a unique configuration for each resonance frequency, - thus far unknown to biology. "Membrane alone fires" is found to be wrong after a century, micro-neuro-filaments communicate prior to firing to decide its necessity and then regulate it suitably. We introduce a series of technologies e.g., fractal grid, point contact, micro THz antenna, to discover that from atomic structure to a living cell, the biomaterials vibrate collectively.

In a coded self-assembly, a simple code is written in the molecule, which self-assembles the molecules into a fractal like structure, which acts as a seed for the next step. As the molecule turns into a complex seed, the code transforms into another form and several seeds self-assemble into another structure, which acts as a seed for the next step. Until now, this technology was considered as a prerogative of nature. Here, a dendritic network is used to write a basic code by synthetically attaching 32 molecular rotors and doping two controller molecules in its cavity. The code live, which is an energy transmission path in the molecule, is imaged. When the energy transmission path or code is triggered, a series of products generate one after another spontaneously. Two examples are: i) dendritic seed (5-6 nm)→paired nanowire (≈12 nm)→nanowire (≈200 nm)→microwire (500 nm)→wire like rod (1-2 μm)→jelly→rectangular sheet (5 μm). ii) dendritic seed→nano-sphere (20 nm)→micro-sphere (500 nm)→large balls(1 μm)→oval shape rod (5-10 μm)→Y, L or T shaped rod assembly. The energy level interactions are tracked using spectroscopy how exactly a directed energy transfer code generates multi-step synthesis from nano to the visible scale. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

To read the signals of single molecules in vitro on a surface, or inside a living cell or organ, we introduce a coaxial atom tip (coat) and a coaxial atomic patch clamp (COAPAP). The metal-insulator-metal cavity of these probes extends to the atomic scale (0.1nm), it eliminates the cellular or environmental noise with a S/N ratio 105. Five ac signals are simultaneously applied during a measurement by COAT and COAPAP to shield a true signal under environmental noise in five unique ways. The electromagnetic drive in the triaxial atomic tips is specifically designed to sense anharmonic vibrational and transmission signals for any system between 0.1nm and 50nm where the smallest nanopatch clamp cannot reach. COAT and COAPAP reliably pick up the atomic scale vibrations under the extreme noise of a living cell. Each protein's distinct electromagnetic, mechanical, electrical and ionic vibrational signature studied in vitro in a protected environment is found to match with the ones studied inside a live neuron. Thus, we could confirm that by using our probe blindly we could hold on to a single molecule or its complex in the invisible domain of a living cell. Our decade long investigations on perfecting the tools to measure bio-resonance of all forms and simultaneously in all frequency domains are summarized. It shows that the ratio of emission to absorption resonance frequencies of a biomaterial is around, only a few in the entire em spectrum are active that regulates all other resonances, like mechanical, ionic, etc.

Nitrogen dioxide (NO2) is considered to be a highly hazardous gas found in combustion engine exhaust, which causes several diseases at a young age. To detect NO2 at room temperature (RT), two-dimensional transition metal dichalcogenides play an essential role because of their greater surface-to-volume ratio. However, their higher limit of detection (LOD), slow response, and incomplete recovery kinetics hinder their use in efficient gas sensors. To mitigate these issues, we fabricate a facile and robust niobium (Nb)-doped molybdenum disulfide (MoS2) sensor using low-pressure chemical vapor deposition on a SiO2/Si substrate. Doping is confirmed through various characterization techniques. As compared to pristine MoS2, three batches of sensors are prepared with different weight percentages of Nb (8, 16, and 24%). Out of these, the 16% Nb-MoS2 sensor gives a greatly enhanced relative response of ∼30% for 500 ppb NO2 at 100 °C with an LOD of 489 ppt. Also, the sensor gives an ultrahigh response of ∼39% (18%) for 50 ppm (500 ppb) NO2 under 0.4 mW/cm2 intensity of UV light and exhibits a lower LOD of 117 ppt at RT. In addition, the 16% Nb-MoS2 sensor shows impressive selectivity toward NO2 against a range of reducing and oxidizing gases, along with exceptional long-term durability and stability. Based on density functional theory calculations, a comprehensive gas sensing mechanism is proposed. The calculations focus on identifying the favorable sites for NO2 adsorption on 16% Nb-MoS2 nanoflakes. This study offers a compelling and practical approach to boosting the efficiency of Nb-MoS2-based NO2 gas sensors. © 2025 American Chemical Society.