Recent advances in terahertz imaging

We review recent progress in the field of terahertz “T-ray” imaging. This relatively new imaging technique, based on terahertz time-domain spectroscopy, has the potential to be the first portable far-infrared imaging spectrometer. We give several examples which illustrate the possible applications of this technology, using both the amplitude and phase information contained in the THz waveforms. We describe the latest results in tomographic imaging, in which waveforms reflected from an object can be used to form a three-dimensional representation. Advanced signal processing tools are exploited for the purposes of extracting tomographic results, including spectroscopic information about each reflecting layer of a sample. We also describe the application of optical near-field techniques to the THz imaging system. Substantial improvements in the spatial resolution are demonstrated. Received: 29 January 1999 / Published online: 7 April 1999     

Regulating the assembly and expansion of the silver cluster from the Ag37 to Ag46 nanowheel driven by heteroanions

Precise control over the shape and size of metal nanoclusters through anion template-driven self-assembly is one of the key scientific goals in the nanocluster community, however, it is still not understood comprehensively. In this work, we report the controllable synthesis and atomically precise structures of silver nanowheels Ag37 and Ag46, using homo (Cl⁻ ions) and heteroanion (Cl⁻ and CrO₄²⁻ ions) template strategies, along with macrocyclic p-phenyl-thiacalix[4]arene and small ⁱPrS⁻ ligands. Structural analyses revealed that in Ag37, Cl⁻ ions serve as both local and global templates, whereas CrO₄²⁻ ions function as local and Cl⁻ ions as global templates in Ag46, resulting in a pentagonal nanowheel (Ag37) and a hexagonal (Ag46) nanowheel. The larger ionic size and more negative charges of CrO₄²⁻ ions than Cl⁻ ions offer more coordination sites for the silver atoms and are believed to be the key factors that drive the nanowheel core to expand significantly. Also, by taking advantage of the deep cavity of thiacalix[4]arene with an extended phenyl group, Ag46 has been used as a host material for dye adsorption depending on the charge and size of organic dyes. The successful use of heteroanions to control the expansion of well-defined silver nanowheels fills the knowledge gap in understanding the directing role of heteroanions in dictating the shape and size of nanoclusters at the atomic level.

A heteroanion self-assembly strategy for regulating the shape and expanding the size of the silver cluster from Ag₃₇ to Ag₄₆ with a macrocyclic (p-phenyl-thiacalix[4]arene) ligand has been presented.     

Computational/In-Silico Methods: An Influential Approach for Drug Designing and Development

As the world is struggling with the pandemic. Various infectious diseases have become a threat to human health. Millions of deaths are caused by these microbial infections (bacterial, fungal, and viral infections). The process of designing and discovering new drugs is very expensive and it also consumes a good amount of time. As per available data, the process of discovery and designing takes 3–20 years to complete. There is a strong urge and demand to discover new methods to make the process of drug design and development more cost-effective. Computational methods are one the novel methods for designing and developing a drug. In this respect, in-silico parameters; ADME (Absorption, Distribution, Metabolism, and Excretion) models have been established with various levels of complication for the transmission of huge data of derivatives/ligands/drugs. Nowadays, in-silico tools are more cost-effective, faster, and simpler than transitional experimental trials. Currently, the pharmaceutical industry faces a huge erosion rate of preclinical and clinical applicants due to the unavailability of pharmacokinetics properties and huge toxicity. These can be minimized via structural modifications of drugs and can help medicinal chemists/pharmacists. In this report, various methodologies and steps have been explained via molecular docking that will lead to drug development in lesser time against various stains.     

The facile and efficient organocatalytic platform for accessing 1,2,4-selenadiazoles and thiadiazoles under aerobic conditions

The first organocatalytic approach towards synthesis of rarely explored 1,2,4-selenadiazole and thiadiazole scaffolds have been devised using corresponding carboxamides as substrates. The transformations were realized using two distinct conditions in the presence of catalytic vitamin B₃ or thiourea under aerobic conditions. Developed methods overcome the associated limitations of previous reported approaches and the desired products were obtained in high yields and selectivity without the formation of toxic side-products.     

Wireless Coupling of Conducting Polymer Actuators with Light Emission

Combining the actuation of conducting polymers with additional functionalities is an interesting fundamental scientific challenge and increases their application potential. Herein we demonstrate the possibility of direct integration of a miniaturized light emitting diode (LED) in a polypyrrole (PPy) matrix in order to achieve simultaneous wireless actuation and light emission. A light emitting diode is used as a part of an electroactive surface on which electrochemical polymerization allows direct incorporation of the electronic device into the polymer. The resulting free-standing polymer/LED hybrid can be addressed by bipolar electrochemistry to trigger simultaneously oxidation and reduction reactions at its opposite extremities, leading to a controlled deformation and an electron flow through the integrated LED. Such a dual response in the form of actuation and light emission opens up interesting perspectives in the field of microrobotics.     

Tuning of Bistability,Thermal Stability of the Metastable States,and Application Prospects in the C3-Symmetric Designs of Multiple Azo(hetero)arenes Systems

Light-responsive molecular systems with multiple photoswitches in C₃-symmetric designs have enormous application potential. The design part of such molecular systems is critical due to its influence in several properties associated with the photoswitches. In order to tune, and in the evaluation of the design–property relationship, we synthesized 18 tripodal systems with variations in the core, linkers, connectivity, and azo(hetero)arene photoswitches. Through extensive spectroscopic and computational studies, we envisaged the factors controlling near-quantitative photoisomerization in both the directions (bistability) and the thermal stability of the metastable states. Furthermore, we also evaluated the impact of designs in obtaining reversible photo-responsive sol-gel phase transitions, solvatochromism, photo- and thermochromism.     

Synthesis,Crystal Structure,and Spectral Study of a Novel Indenoimidazole Carboxylic Acid Amide

Russian Journal of Organic Chemistry - 3a,8a-Dihydroxy-2,8-dioxo-1,3a,8,8a-tetrahydro-2H-indeno[1,2-d]imidazole-3-carboxamide has been synthesized in 85% yield from ninhydrin and biuret via a green...     

Miniature Non-thermal Plasma Induced Cell Cycle Arrest and Apoptosis in Lung Carcinoma Cells

Plasma Chemistry and Plasma Processing - Non-thermal plasma has been a promising new cancer treatment modality in plasma oncology field. It generates extracellular and intracellular reactive...     

Influence of 120 MeV S9+ ion irradiation on structural,optical and morphological properties of zirconium oxide thin films deposited by RF sputtering

The calibrated and controlled swift heavy ions (SHI) beam irradiation generate defects which can cause modifications in various properties of the materials such as structural, optical, magnetic, morphological, and chemical etc. The passage of ion through the target material causes the nuclear energy losses ($S_n$) and electronic energy losses ($S_e$). The $S_e$ dominates over $S_n$ in SHI irradiation. In the present study, ZrO₂ thin films were grown on silicon and glass substrate by using RF sputtering deposition technique. For the purpose of modifications induced by swift heavy ions, these films were irradiated by a 120 MeV S⁹⁺ ion beam of 1 pnA current, with varying ion fluences from 5E12 to 1E13 ions/cm², using the tandem accelerator at the Inter University Accelerator Center (IUAC), New Delhi, India. The X-ray diffraction (XRD) patterns confirmed the formation of monoclinic and tetragonal phases and it was observed that XRD peaks intensity increased up to the fluence of 5E12 ions/cm² followed by opposite behavior at higher fluences. Atomic force microscope (AFM) study revealed the increased surface roughness after SHI irradiation. In addition to it, the formation of electronic transition states in optical band gap region and enhancement of absorption edge was observed from UV-visible spectroscopy (UV-Vis) results due to which direct band gap energy value decreased from those of un-irradiated samples. Photoluminescence (PL) broad emission spectra were determined using the excitation wavelength at 290 nm with the prominent peak at 415 nm which can be ascribed to Zr vacancies due to band edge emission as a result of free-exciton recombination. Rutherford backscattering spectrometry (RBS) technique was used for depth profiling and elemental composition in zirconia thin films. The expected role of electronic energy loss during ion irradiation is to modify the properties of the material has been discussed.