We report a unique approach for producing few-layer graphene from graphite utilizing natural surfactants (Jatropha Curcas and Acacia Concinna) and liquid-phase exfoliation in water. Raman spectroscopy revealed an ID/IG ratio of 2.54 for graphene extracted from Jatropha Carcus (JG) and 0.79 for graphene extracted from Acacia Concinna (AG), along with a higher number of deconvoluted peaks in the 2D band for AG. These findings suggest a higher number of graphene layers and a lower defect density in the AG sample compared to the JG sample. It is also observed that AG forms a bubbly-graphene morphology. These flakes are further transformed into graphene foam. The AG graphene foam material (AGFM) presents decorated porosity on the melamine base with larger pore diameters (1 to 2 µm), whereas the JG foam material (JGFM) has flake-like morphology on it. These morphological variations impact the produced foams' ability to attenuate sound. A cost-effective smartphone-based setup developed in our laboratory was employed to assess the sound attenuation properties of the synthesized foam materials. Results demonstrate that AGFM effectively attenuates sound ( 99

This manuscript presents our recent investigations on the effects of swift heavy ion irradiation on the electrical properties of Hafnium Titanium Oxide (HfTiOx)-based Metal Oxide Semiconductor (MOS) devices. Al/HfTiOx/Si MOS devices were irradiated with 120 MeV Ag9+ ions over a range of fluences (1 E 11-1 E 13 ions/cm(2)). A systematic study on defects generated by heavy ion irradiation on MOS devices has been analysed thoroughly by using current-voltage (I-V) and capacitance-voltage (C-V) measurements. The radiation damage on these devices is explained by examining the role of various conduction mechanisms observed in leakage currents before and after irradiation. Hence, this work will provide valuable insights regarding radiation damage in HfTiOx-based MOS devices in space and medical applications.

We report on ion-induced phase transformations, defect dynamics related to oxygen vacancies and the resulting leakage current characteristics of RF sputtered HfO2 thin films grown on GaAs. A systematic growth of HfO2 grains and ion prompted phase transformations of HfO2 to crystalline phases such as monoclinic and tetragonal/orthorhombic (mixed phase) in otherwise amorphous HfO2 thin films have been observed after irradiation. At lower fluences, ion induced enhancement in the dielectric properties of HfO2 thin films resulted in a reduction in the leakage current, whereas ion prompted defect formation at higher fluences caused a systematic increase in the leakage current density. Further, the effects of Poole-Frenkel tunneling and Fowler-Nordheim tunneling on the leakage current have also been investigated. These mechanisms showed the existence of impurities in the as-grown films. Photoluminescence study suggests that the variation in the defect configuration related to O-vacancies and the slight shift in the peak positions due to swift heavy ion irradiation are responsible for the observed changes in electrical characteristics. This study offers worthwhile information for considering the effects of electronic excitation prompted defect annealing and defect creation on the performance of HfO2/GaAs based photonic and optoelectronic devices, particularly, when such devices are operated in a radiation harsh environment.

The wettability of nanomaterials has been studied for solid and liquid interface-based scientific curiosity. Specifically, the nature of thin-film coatings has been consistently studied in relation to the wettability of ceramic and dielectric non-conducting materials, which is directly related to surface free energy (Zenkin, S.; Belosludtsev, A.; Kos, S.; Cerstvy, R.; Haviar, S.; Netrvalova, M. Thickness Dependent Wetting Properties and Surface Free Energy of HfO2 Thin Films. Appl. Phys. Lett. 2016, 108, 231602). There has been a great deal of interest in the development of such materials with fine-tunable surface free energy and sufficient stability in challenging environments (Preston, D.J.; Mafra, D.L.; Miljkovic, N.; Kong, J.; Wang, E.N. Scalable Graphene Coatings for Enhanced Condensation Heat Transfer. Nano Lett. 2015, 15, 2902, Chen, C.; Cai, Q.; Tsai, C.; Chen, C.; Xiong, G.; Yu, Y.; Ren, Z. Dropwise Condensation on Superhydrophobic Surfaces with Two-Tier Roughness. Appl. Phys. Lett. 2007, 90, 173108). One of the characteristic transition metal oxides, namely hafnium oxide (HfO2), has recently been investigated for use in strong coating materials by examining its surface free energy. However, the surface free energy of HfO2 films has not been thoroughly understood. The interpretation of HfO2 surface free energy and intrinsic wettability still has scientific interest, apart from the fact that the previously reported water contact angle of HfO2 thin or bulk films varies greatly across the published literature. In this work, we thoroughly examined the surface free energy fluctuation in HfO2 films made by RF magnetron sputtering after precisely controlling the film thickness by altering the deposition time. We have examined the thickness and chemical makeup of HfO2 films, in addition to other characteristics. In fact, we investigated the dependence of HfO2 film thickness on variations in wettability. RF sputtering of HfO2 thin films demonstrated that our experimental findings will advance our understanding of the surface free energy of thin-film HfO2 and its scientific foundations. These findings may also lead to practical uses such as liquid separation and purification using HfO2 as a durable coating. Furthermore, RF sputtering HfO2-based thin films have demonstrated switching behavior and may be used as memory devices.

Ag and Au nanoparticles (NP), along with carbon quantum dots (CQD), were synthesized using straightforward methods. Ag NP exhibit localized surface plasmon resonance (LSPR) at 445 nm and Au NP at 551 nm. The quantum yield of as-synthesized CQD in water has been found to be 0.46 at 350 nm excitation. Nanocomposites (Au-CQD, Ag-CQD, Ag–Au, and Ag–Au-CQD) were used as surface enhanced Raman scattering substrates for methylene blue (MB) detection. At 785 nm excitation, Ag-CQD and Ag–Au-CQD showed higher analytical enhancement factors (AEFs) of 1.1 ×104 and 2.5 ×104, respectively, compared to Ag–Au (0.7 ×104). At 514 nm, simultaneous excitation of Ag and Au LSPR improved AEFs, especially for Ag–Au (1.7 ×104) and Ag–Au-CQD (1.8 ×104). Detection limits reached 10−7 M for Au-CQD and 10−8 M for others at 785 nm, while all composites showed a uniform detection limit of 10−8 M at 514 nm. AEFs were reproducible with ∼2%–9% relative standard deviation. Furthermore, COMSOL Multiphysics was used to analyze electric field distribution and establish a strong correlation between theoretical EFs and experimental AEFs in Ag–Au and Ag–Au-CQD nanocomposites. Additionally, photoinduced enhanced Raman scattering (PIERS) studies under 445 nm illumination revealed enhanced Raman signals via photoinduced charge transfer from CQD to metal NP. The highest enhancement was observed in Ag–Au-CQD, followed by Ag-CQD and Au-CQD, while Ag–Au without CQD showed minimal effects. Thus, the dual-wavelength approach enhances PIERS performance for sensitive MB detection.

The AlCuFe icosahedral quasicrystal (IQC) targets prepared using two different methods- (1) vacuum induction melting followed by annealing, and (2) spray forming, have been subjected to femtosecond laser ablation in deionized water (DI water) for 54 min. High-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) pattern analysis of the synthesized nanoparticles (NPs) revealed the presence of IQC phases. NPs obtained from the induction-melted IQC target contained Al _13 Fe _4 and β -Al(Fe,Cu) phases along with the IQC phase, reflecting the phase composition of the bulk target. In contrast, NPs from the spray-formed target exhibited only the IQC phase. Both samples also showed the presence of CuO and amorphous Al _2 O _3 . The ablated region of the target surface showed the formation of grooves and bumps. In addition, the formation of liquid vortices during the ablation process was ascertained by the presence of macropores in the ablated region of the target’s surface. I-V plots obtained from the ablated region and the non-ablated region of the target’s surface revealed an increase in the resistance post-ablation. This increase is attributed to the presence of defects and surface oxidation that incurred during the laser irradiation.

Germanium (Ge)-SiO2 composite films fabricated by using radio frequency magnetron co-sputtering were subjected to nanosecond (ns) laser pulse irradiation. The intense laser irradiation effects on as deposited composite films lead to the modification and the formation of Ge nanocrystals (NCs) embedded in SiO2. The as-deposited and laser treated samples have been characterized with X-ray diffraction (XRD) and micro-Raman spectroscopy to understand the formation of Ge NCs due to laser irradiation. The respective Ge NCs related peaks in XRD pattern as well as the Ge-Ge related optical phonon vibrational peaks in micro-Raman spectra confirm the formation of Ge NCs. Transmission electron microscopy images indicate the formation of Ge NCs after the laser irradiation. The effects of laser pulse energy and the irradiation time play a vital role in the crystallization of the as-deposited films. The changes in the Ge NCs size related shifts in the peak position of Ge optical phonons from the Raman spectra of the respective samples are explained with Ge-Ge optical phonon vibrational model. The observed photoluminescence emission in the green and red region of the visible spectrum from the laser treated samples are explained using the phenomenon of creation of Ge NCs in the Ge+SiO2 composite films and the oxygen defects created in SiO2 during the ns laser treatment.

We report a study on the effects of O 2 /Ar ratio on the resistive switching properties of HfO x thin-films deposited by using RF magnetron sputtering. Ar is kept at a constant flow rate of 30 SCCM and O 2 is varied from 0 to 30 SCCM during the deposition of these thin films. The UV–Vis spectra reveled that the transmission percentage of these films increase proportionally with increase of O 2 /Ar ratio up to a critical value. Further, the peak positions at 2.7 and 2.9 eV in PL spectra were attributed to singly and doubly charged oxygen vacancies respectively. These defects and vacancies alter the switching behavior of the devices. Moreover, the XPS data showed that the intensity of O–O bond peak decreases as O 2 /Ar ratio increases. Therefore, the switching performance shows a significant influence of the amount of inletting the oxygen gas with Ar during the deposition, thereby an improvement in the resistance ratio (R off /R on ) of these HfO x based devices is noticed.

In this work, we present a detailed study on the effects of energetic ions and gamma irradiation on the performance of non-stoichiometric tantalum oxide (TaO x ) based Metal Oxide semiconductor (MOS) capacitors. The leakage current is found to increase after a critical fluence (5E12 ions/cm 2 ) of 120 MeV Ag ion irradiation. Whereas the accumulation capacitance decreased drastically upon the initial fluence and the hysteresis loop is intact even at higher doses. The order of leakage current and accumulation capacitance remained almost the same in the case of gamma irradiation though there are minor variations as a function of dose. Photoluminescence studies indicated specific changes in the density of various types of defects in both ion and gamma irradiation samples. The observed changes in the electrical properties of these devices are consistent with the nature and density of various defects. The study suggests that the TaO x-based MOS devices can sustain higher doses and are capable of working in radiation-harsh environments.

We present green synthesis of silver nanoparticles in water using unirradiated and Ag ^15+ ion irradiated phytoextracts of Bergenia Ciliata leaf, Eupatorium adenophorum leaf, Rhododendron arboreum leaf and flower. The use of different plant extracts and their subsequent ion irradiation allow for successful refinement of nanoparticle size and morphology. Due to changes in reducing and capping agents the nanoparticle surface functionalization also varies which not only controls the morphology but also allows for surface oxidation and aggregation processes. In this work, we have synthesized silver nanoparticles which exhibit sizes in the range from 13 to 24 nm and having shapes like spherical, quasispherical, trigonal, hexagonal, cylindrical, dendritic assemblies, and porous nanoparticles. Owing to changes in the size and shape of the nanoparticles, their direct bandgap (2.05 eV - 2.48 eV) and local surface plasmon resonance (420 nm - 490 nm) could also be tuned. These nanoparticles are examined as SERS substrates, where their enhancement factors, limit of detection for methylene blue, and SERS substrate homogeneity have been tested. It has been observed the nanoparticles synthesized using unirradiated plant extracts present an enhancement factor of 10 ^6 with a limit of detection 10 ^-8 M. Whereas nanoparticles with refined morphology and shapes upon irradiation present high enhancement factors of >10 ^7 and detection limit down to 10 ^-9 M. In addition, uniformity in Raman spectra over the SERS substrates has been obtained for selected Ag NPs substrates synthesized using irradiated extracts with minimum relative standard deviation in enhancement factor < 12

In the present work, the effects of 100 MeV Si ions on the structural and optical properties of GeOx thin films have been investigated. Thin films of Germanium oxide (GeOx) were deposited onto silicon substrates using electron beam evaporation technique. Subsequently, 100 MeV Si7+ ions were used to irradiate as-deposited films at different fluences ranging from 5 x 1012 to 2 x 1013 ions/cm2. As-deposited films are amorphous as evident from XRD and Raman results. After irradiation with a fluence of 5 x 1012 ions/cm2 the films show partial crystallization. The strong photoluminescence (PL) exhibited from as-deposited and irradiated films is in ultraviolet (UV) and blue region. The blue shift was observed in PL bands after ion beam irradiation. PL band intensity was found to vary with irradiation fluence. The possible mechanism of variation in the PL emission from GeOx thin films with Si ion irradiation has been studied.

Over the last 20 years, optical fiber-based devices have been exploited extensively in the field of biochemical sensing, with applications in many specific areas such as the food processing industry, environmental monitoring, health diagnosis, bioengineering, disease diagnosis, and the drug industry due to their compact, label-free, and highly sensitive detection. The selective and accurate detection of biochemicals is an essential part of biosensing devices, which is to be done through effective functionalization of highly specific recognition agents, such as enzymes, DNA, receptors, etc., over the transducing surface. Among many optical fiber-based sensing technologies, optical fiber interferometry-based biosensors are one of the broadly used methods with the advantages of biocompatibility, compact size, high sensitivity, high-resolution sensing, lower detection limits, operating wavelength tunability, etc. This Review provides a comprehensive review of the fundamentals as well as the current advances in developing optical fiber interferometry-based biochemical sensors. In the beginning, a generic biosensor and its several components are introduced, followed by the fundamentals and state-of-art technology behind developing a variety of interferometry-based fiber optic sensors. These include the Mach-Zehnder interferometer, the Michelson interferometer, the Fabry-Perot interferometer, the Sagnac interferometer, and biolayer interferometry (BLI). Further, several technical reports are comprehensively reviewed and compared in a tabulated form for better comparison along with their advantages and disadvantages. Further, the limitations and possible solutions for these sensors are discussed to transform these in-lab devices into commercial industry applications. At the end, in conclusion, comments on the prospects of field development toward the commercialization of sensor technology are also provided. The Review targets a broad range of audiences including beginners and also motivates the experts helping to solve the real issues for developing an industry-oriented sensing device.

Carbon based nanomaterials (CBNs) such as multi walled carbon nanotubes (MWCNTs), graphene etc have attracted huge interest due to their widespread applications in contemporary nanotechnology. The ion bombardment is an important method which can be used for tuning of the structural and morphological properties of the CBNs. In the present work, we have carried out ion irradiation on MWCNTs (prepared by chemical vapour deposition method) with 5 MeV Si ions at different fluences ranging from 1 x 1014 to 5 x 1016 ions/cm2. The resulting structural and morphological modifications on the pristine MWCNTs have been characterized by using X-ray diffraction, Raman spectroscopy and field emission scanning electron microscopy. Results observed after successful characterization are compared with pristine sample results and we observed that the irradiation creates defects in MWCNTs and causes amorphized carbon nanomaterials depending on the fluence and energy deposited by energetic ions inside the MWCNTs.

We report a study of the role of material's conductivity in determining the morphology of nanoparticles and nanostructures produced by ultrafast laser ablation of solids. Nanoparticles and textured surfaces formed by laser ablation display a wide variation in size and morphology depending on the material. In general, these qualities can be grouped as to material type, insulator, semiconductor, or metal; although each has many other different material properties that make it difficult to identify the critical material factor. In this report, we study these nanoparticle/surface structural characteristics as a function of silicon (Si) resistivity, thus honing-in on this critical parameter and its effects. The results show variations in morphology, optical, and nonlinear properties of Si nanoparticles. The yield of colloidal Si nanoparticles increased with an increase in the conductivity of Si. Laser-induced periodic surface structures formed on ablated substrates are also found to be sensitive to the initial conductivity of the material. Further, the laser ablation of Gamma-irradiated Si has been investigated to verify the influence of altered conductivity on the formation of Si nanoparticles. These observations are interpreted using the basic mechanisms of the laser ablation process in a liquid and its intricate relation with the initial density of states and thermal conductivities of the target material.

In this study, water dispersible fluorescent carbon quantum dot (CQD) has been synthesised, having an average size of 8.6 ± 0.4 nm using Cynodon dactylon (CD) following microwave assisted green synthetic one-step method. As-prepared CQD fluoresces strongly at 444 nm having a quantum yield of 1% in water when excited at 350 nm. This fluorescence of CQD is sensitive toward As3+ and Fe3+ metal ions. These CQD are utilized for dual metal ion fluorescence sensing; turn-on fluorescence sensing for As3+ and turn-off fluorescence sensing for Fe3+ ions. Limit of detection for As3+ and Fe3+ ions has been found to be 19 nM and 0.10 μM respectively, which is the lowest value reported for As3+ without any functionalization. The adsorption kinetics of As3+ and Fe3+ ions on CQD have been examined using pseudo-first-order-kinetic model revealing that physical adsorption is dominant over chemical processes in this work. For 0.41 g/L and 1.90 g/L dose of CQD, the equilibrium adsorption capacity was found to be 1.57 × 10−6 mg/g, 2.91 × 10−7 mg/g, and 1.01 × 10−5 mg/g, 1.69 × 10−6 mg/g respectively for As3+ and Fe3+ ions. Despite having low quantum yield in water, as-prepared CQD showed low cytotoxicity and good tolerance against photodegradation of biological cells at concentrations lower than 62.5 μg/mL and when the cells are illuminated up to 12 h. Owing to this, the synthesised CQD have been utilized as fluorescent probes for in itro cell imaging.

The synthesis of Ge nanocrystals (NCs) by using ion implantation method is reported here along with the results from different spectroscopic and microscopic characterizations such as Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD), Raman spectroscopy, photoluminescence (PL), and atomic force microscopy (AFM). Various fluences of 1 MeV Ge ions have been implanted into SiO2, and then, as-implanted samples were annealed using rapid thermal annealing system for the synthesis of Ge NCs. The Ge NCs presence was confirmed from Raman spectroscopy and XRD measurements. The low-fluence implanted sample did not show any signature of Ge NCs, whereas Ge NCs presence has been observed in the high-fluence implanted sample after annealing. The mechanism of Ge NCs formation in the as-implanted samples after annealing has been discussed.

The research investigates the elemental composition of hot-spring water in Sikkim, specifically in Yumthang, Tarum, and Reshi, using laser-induced breakdown spectroscopy. This technique involves exciting the sample with a high-energy laser pulse, causing it to emit light that can be analyzed to determine its elemental composition. The results of the study indicate that the hot-spring water in Sikkim is of meteoric origin, meaning it originated from precipitation. To understand the abundance of elements in the hot-spring water samples, the Sulphur/Nitrogen, Chlorine/Nitrogen, and Sulphur/Chlorine ratios were calculated using the ratiometric method. These ratios were then used to classify the samples using univariate and multivariate statistical tools. The box plot was used for the univariate analysis, while the bivariate normal distribution method was used for the multivariate analysis. We have also discussed the limitations of overlapping emission peaks on the classification of the samples. The study found that the abundance of nitrogen in the samples played a significant role in their classification. Principal component analysis was also employed to classify the samples. This technique involves identifying the most significant variables contributing to the variation in the data and using them to classify the samples. Overall, the study provides important insights into the elemental composition of hot-spring water in Sikkim and highlights the usefulness of laser-induced breakdown spectroscopy in analyzing such samples.