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Studies on structural and optical properties of pure and transition metals (Ni, Fe and co-doped Ni–Fe) doped tin oxide (SnO2) nanoparticles for anti-microbial activity
摘要： In this present work, pure and transition metal ions (Ni, Fe and co-doped Ni–Fe) doped SnO2 nanoparticles (NPs) were synthesized using a simple chemical co-precipitation method. Transition metal ions (Ni, Fe and co-doped Ni–Fe) were doped in order to study the influence of structural and optical properties. The synthesized samples were analyzed by using powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, UV–Visible spectroscopy, FT-IR, and photoluminescence spectroscopic techniques. SnO2 crystallites were found to exhibit tetragonal rutile structure with space group P42/mnm (136) with average particle size in the range of 20–30 nm. Also confirmed that all the doped metal ions were incorporated to SnO2. The UV–Vis-NIR spectroscopy revealed a significant red shift in the absorbing band edge due to increase in the amount of Ni, Fe and co-doped Ni–Fe contents. The SEM image shows the morphology of pure and doped (Fe, Ni and Fe–Ni co-doped) SnO2 NPs with large spherical shapes. In FT-IR spectra, the strong peaks are attributed to the antisymmetric stretching mode of O-Sn-O. The PL spectrum exhibits a strong blue emission peak. The antimicrobial studies were investigated against standard bacterial strains and enhanced anti-bacterial activity in doped and co-doped samples was observed, which can be attributed to the ROS and the particles were in the nanoscale regime.
关键词： Antibacterial activity,Photoluminescence,Co-precipitation,Nanoparticle,Co-dopant
更新于2025-09-23 15:23:52
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Highly Responsive PEG/Gold Nanoparticle Thin Film Humidity Sensor via Inkjet Printing Technology
摘要： In this study, a highly responsive humidity sensor is developed by printing gold nanoparticles (GNP) grafted with a hygroscopic polymer. These GNPs are inkjet printed to form a uniform thin film over an interdigitated electrode with controllable thickness by adjusting the printing parameters. The resistance of the printed GNP thin film decreases significantly upon exposure to water vapor and exhibits a semi-log relationship with relative humidity (RH). The sensor can detect RH variations from 1.8% to 95% with large resistance changes up to 4 order of magnitude with no hysteresis and small temperature dependence. In addition, with a thin thickness, the sensor can reach absorption equilibrium quickly with response and recovery times of ≤1.2 and ≤3 seconds, respectively. The fast response to humidity changes also allows the GNP thin film sensor to distinguish signals from intermittent humidification/dehumidification cycles with a frequency up to 2.5 Hz. The printed sensors on flexible substrates show little sensitivity to bending deformation and can be embedded in a mask for human respiratory detection. In summary, this study demonstrates the feasibility of applying printing technology for the fabrication of thin film humidity sensors, and the developed methodology can be further applied to fabricate many other types of nanoparticle based sensor devices.
关键词： inkjet printing,respiratory monitoring,Humidity sensor,gold nanoparticle,poly(ethylene glycol)
更新于2025-09-23 15:23:52
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Binary Colloidal Nanoparticle Concentration Gradients in a Centrifugal Field at High Concentration
摘要： Binary colloidal nanoparticles have been found to form different types of crystalline phases at varied radial positions in a centrifugal field by Chen et al (ACS nano 2015, 9, 6944-50.). The variety of binary phase behaviors resulted from the two different nanoparticle concentration gradients but to date the gradients can only be empirically controlled. For the first time, we are able to measure, fit and simulate binary hard sphere colloidal nanoparticle concentration gradients at high particle concentration up to 30 vol%, which enables tailor-made gradients in a centrifugal field. By this means, a continuous range of binary particle concentration ratios can be accessed in one single experiment to obtain an extended phase diagram. By dispersing two differently sized silica nanoparticles labeled with two different fluorescence dyes in a refractive index matching solvent, we can use a Multi-Wavelength Analytical Ultracentrifuge (MWL-AUC) to measure the individual concentration gradient for each particle size in sedimentation-diffusion equilibrium. The influence of the remaining slight turbidity at high concentration can be corrected using the MWL spectra from the AUC data. We also show that the experimental concentration gradients can be fitted using a non-interacting non-ideal sedimentation model. By using these fitted parameters, we are able to simulate nanoparticle concentration gradients, which agreed with the subsequent experiments at a high concentration of 10 vol% and thus allowed for the simulation of binary concentration gradients of hard sphere nanoparticles in preparative ultracentrifuges (PUC). Finally we demonstrated that by simulating the concentration gradients in PUC, a continuous and extended binary nanoparticle phase diagram can be obtained by simply studying the structure evolution along the centrifugal field for one single sample instead of a large number of experiments with discrete compositions in conventional studies.
关键词： high particle concentration,binary nanoparticle phase diagram.,Binary nanoparticle concentration gradients,sedimentation-diffusion equilibrium
更新于2025-09-23 15:22:29
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Synthesis of Chiral Gold Nanoparticle by Direct Reduction with L and D-Serine and Enhanced Anti-Mycobacterial Activity by D-Serine Protected Gold Nanoparticle
摘要： Current situation demands more biocompatible and non-toxic nanostructures. Towards this the present study describes the synthesis of gold nanoparticle by direct reduction of tetrachloroauric acid with both D- and L-enantiomeric forms of the amino acid serine. The formation of nanoparticle was confirmed by examining different physical characteristics like surface plasmon resonance. Moreover, the retention of chirality of the reduced particle was also evident from circular dichroism spectroscopy experiment. In addition, the shielding of the nanoparticle by respective amino acid was confirmed by Scanning Electron Microscope and Energy Dispersive X-ray Analysis (SEM-EDAX). As D-serine is known to be active against Mycobacteria, examination of the biological activity of the D-serine protected particle was performed against the same. The result showed higher inhibitory activity of the particle against Mycobacterium smegmatis than D-serine alone. Thus the present study describes a new protocol for the synthesis of chiral gold nanoparticle that can be beneficial in enantioselective biological applications.
关键词： Chiral nanoparticle,D-serine,Mycobacteria,Biocompatible gold nanoparticle,L-serine
更新于2025-09-23 15:22:29
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Fabrication of Stretchable Circuits on Polydimethylsiloxane (PDMS) Pre-Stretched Substrates by Inkjet Printing Silver Nanoparticles
摘要： Several research methodologies have recently been developed to allow for the patterning of conductive lines on elastomeric rubber substrates. Specifically, various conductive materials, substrates, and fabrication techniques were investigated to develop stretchable circuits. One promising technique recommends the application of axial strain on an elastomer substrate prior to patterning conductive lines on it. When the substrate is released, conductive lines buckle to form waves, making the circuit stretchable. However, the majority of applications of stretchable circuits require fitting them to two-dimensional surfaces, such as the human body. Hence, in this paper we propose the concept of radial pre-stretching of the substrates to enhance the stretchability of the fabricated circuits. In particular, straight silver conductive lines were deposited on a polydimethylsiloxane (PDMS) surface using inkjet printing technology, and subsequently tested under both axial and radial loads. Radial pre-stretching was compared to axial pre-stretching, resulting in an improved performance under radial loads. The optimal performance was achieved by pre-stretching the PDMS substrate with a radial strain of 27%. This resulted in stretchable circuits which could sustain radial loads with an average breakdown strain of approximately 19%. Additionally, horseshoe patterns were printed on radially pre-stretched PDMS substrates and their performance was compared to that of their straight line counterparts. Though these patterns are generally favorable for the fabrication of stretchable circuits, the optimal horseshoe pattern examined in this study could only sustain up to 16% radial strain on average when radially pre-stretched by 27%.
关键词： PDMS,inkjet printing,stretchable circuits,pre-stretching,sensors platform,silver nanoparticle ink
更新于2025-09-23 15:22:29
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Hydration accelerator and photocatalyst of nanotitanium dioxide synthesized via surfactant-assisted method in cement mortar
摘要： To develop TiO2-based cement materials, the effect of TiO2 on the cement hydration and photocatalytic reaction should be investigated. The phase, size and shape of TiO2 are important factors for better understanding its application in cement. TiO2 nanoparticles were synthesized by a surfactant-assisted, reverse micelle method to control phase, size and shape by three selected surfactants namely: sodium dodecyl sulfate (SDS), cetyl trimethylammonium bromide (CTAB) and TritonX-100. The synthesized TiO2 nanoparticles were characterized by XRD, SEM and TEM for observation of phase, size and shape. The modified micro structures of admixed cements with the different synthesized TiO2 nanoparticles incorporated were also examined by SEM. Particularly, the hydration process and photocatalytic reaction of the cement mixture were evaluated by heat flow calorimetry and methylene blue (MB) degradation, respectively. Results showed that anatase-rich and smaller size TiO2 nanoparticles provided accelerated cement hydration and the ability to degrade MB photocatalytically at the surface of admixed-TiO2 cement.
关键词： Surfactant-assisted method,Photocatalytic activity,Hydration,Cement,Titanium dioxide nanoparticle
更新于2025-09-23 15:22:29
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Effects of low-temperature sintering on surface morphology and electrical performance of silver nanoparticle/carbon nanotube composite films
摘要： Silver nanoparticle (AgNP)/carbon nanotube (CNT) composites are drawing increasing attention for several applications, especially where transparency is required. However, interfacial interaction and stability of the AgNP/CNT composites have been scarcely investigated. In the present study, transparent coatings were prepared from dispersed AgNP-coated multiwalled CNTs and exposed to different annealing conditions. The changes in surface morphology and evolution of interfacial configuration of AgNP-decorated CNT transparent composite films were investigated. Under certain conditions, CNT ropes were glued to one another by the melted AgNP aggregates, resulting in the improvement of the measured electrical properties. The in situ measurements of the electrical properties allowed correlating the AgNPs sintering mechanism with the morphological observations. Notably, at a given temperature, increasing the initial film density increased the time necessary to complete the AgNPs sintering. The obtained results show that the electrical resistance can be used as a tool to indirectly monitor the network state of transparent AgNP-decorated CNT composite films, hence paving the way to tuning the composite film properties with a high precision for the desired application. These findings also explain the mechanism of reinforcement of polymer nanocomposites by the current nanofillers.
关键词： A. Silver nanoparticle,B. Carbon nanotube,E. In situ monitoring,D. Sintering,F. Electrical properties,C. Nanocomposite
更新于2025-09-23 15:22:29
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Investigation of a low cost tapered plastic fiber optic biosensor based on manipulation of colloidal gold nanoparticles
摘要： We demonstrate a low cost Tapered Fiber Optic Biosensor (TFOBS) based on manipulation of colloidal gold nanoparticle in the evanescent field of tapered fiber. The sensor consists of a biconical tapered plastic optical fiber with colloidal gold nanoparticles coated on the tapered region. The strength of evanescent field absorption as a function of gold nanoparticle size is evaluated using Finite Difference Time Domain simulation. Simulation results suggest that in order to achieve maximum absorption in visible range of wavelength, the size of the gold nanoparticle should be in the range 3-4 nm. Gold nanoparticle of desired size is then synthesized and coated on the tapered region to fabricate a TFOBS. It is found experimentally that coating of gold nanoparticles enhances the fraction of light coming out to the cladding surface. This is explained as a consequence of local surface plasmonic resonance. The TFOBS is then tested for its sensing application to detect Bovine Serum Albumin. Level of detection of the proposed sensor is calculated and is found as 0.326gm/dL.As normal albumin level in healthy human blood serum is between 3.5 to 5.5gm/dL, the proposed TFOBS can be used as a low cost accurate albumin sensor.
关键词： Tapered Fiber Optic Sensor,Local Surface Plasmon Resonance,Manipulation of nanoparticle
更新于2025-09-23 15:22:29
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Facile Sol-gel Synthesis of Metaloxide Nanoparticles in a Cellulose Paper Template
摘要： Ensembles of free standing particles of titanium, zinc, copper and iron oxides of 6-109 nm in size were sol-gel synthesized with a use of a cellulose paper as a template. The calcination time as short as 60 min at 550°C in air was found to be sufficient for the formation of crystalline single phase TiO2 or ZnO nanoparticles, Cu2O+CuO or Fe2O3+Fe3O4 nanocomposites and to burn out the organic components. The impurities initially present in the cellulose (Сa, Na, Cl) were detected in the synthesized compounds.
关键词： Sol-gel synthesis,Zinc oxide,Nanoparticle,Copper oxides,Cellulose,Iron oxides,Titanium oxide
更新于2025-09-23 15:22:29
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Indium tin oxide modified with dendrimer-encapsulated Pt nanoparticles as efficient p-aminophenol redox cycling platforms
摘要： In this work, we studied indium tin oxides (ITOs) modified with dendrimer-encapsulated Pt nanoparticles (Pt DENs) to develop efficient p-aminophenol (p-AP) redox cycling platforms. The ITO surfaces were modified via electro-oxidative grafting of the terminal amine groups of the dendrimers encapsulating catalytic Pt nanoparticles (i.e., Pt DENs). Compared to conventional ITO surfaces, the Pt DEN-modified ITOs showed highly enhanced electrochemical oxidation current of p-AP even at low potentials with no significant background oxidation current due to the catalytic activity of Pt nanoparticles, leading to high signal-to-background ratio for sensitive p-AP redox cycling. The enhanced p-AP redox cycling on the Pt DEN-modified ITOs led to ～17.8 times higher sensitivity of the p-AP redox cycling than that obtained with conventional ITOs. In addition, the Pt DEN-modified ITOs were found to be suitable as platforms for the immobilization of oligonucleotides due to the globular structure of dendrimers, which have a high surface-to-volume ratio and multiple terminal functional groups, grafted on ITO surfaces. The DEN-modified ITOs could be further functionalized by the immobilization of single-strand DNA oligonucleotides with high surface density (i.e., (2.2 ± 0.4) × 1012 molecules/cm2), which is ～4.4-fold higher than that on the surface of conventional ITOs.
关键词： Indium tin oxide (ITO),Amine-terminated dendrimer,p-aminophenol (p-AP) redox cycling,Dendrimer-encapsulated nanoparticle (DEN)
更新于2025-09-23 15:22:29