197 research outputs found
Sensing of Inorganic Ions and Organic Molecules Using Fluorescence and Plasmonic Nanomaterials
No full textNanomaterials are the emerging star in the field of sensor for the determination of various toxins and biomolecules. The SPR and Fluorescence active nanomaterials attained wide scope due to their fast response towards the external moieties. Thesis involves various segments i.e. synthesis of different size AuNPs and surface passivated carbon dots (C-dots). The morphology and surface composition of nanomaterials were characterized by HRTEM, FTIR and XPS. These materials were used to sense various metal ions (such as Fe+3, F-, Cu+2 ions etc.) and biomolecules like picric acid (PA), thiopurines and creatinine respectively. Large AuNPs exhibited high selectivity for thiopurines with LOD = 0.0001mM. The surface passivation in C-dots modulates its quantum yield (58-30%) and average lifetime (~2.2 ns). The C-dots enriched with pyrrolic and pyridinic moieties exhibited high selectivity for creatinine with LOD = 36 nM whereas C-dots prepared from citrus limetta showed effective response for F- ions
Synthesis of Bi2O3/Sb2S3 Nanocomposite for Photocatalytic Degradation of Rhodamine-B and Tetracycline
No full textThe application of photocatalytic decomposition has garnered significant interest as a viable approach to mitigate water contamination and environmental pollution. In the face of expanding industrial development and rapid population increase, water pollution poses a grave threat to the ecosystem and human well-being. This study employs a hydrothermal technique to synthesize the photocatalyst by varying the mole ratios of Bi2O3 and Sb2S3. Loading Sb2S3 onto Bi2O3 enables broad-spectrum solar light absorption, efficient segregation of charges, and enhanced surface area. The characteristics of the elements were thoroughly examined through XRD and XPS techniques, enabling analysis of the crystal structure, chemical valence, and surface chemical makeup. The formation of smaller Sb2S3 nano-rods, effectively deposited onto bigger Bi2O3 nano-rods, was visually confirmed via SEM and TEM images. The EDS spectra evidenced the even dispersion of elements. PL and UV–DRS spectroscopy provided evidence of low charge recombination and a narrow band gap, indicating appropriate traits for photocatalysis. Furthermore, BET analysis revealed the photocatalyst's extensive surface area and mesoporous nature. Remarkable decomposition efficiencies were achieved, with a 98.2% degradation rate (rate constant = 0.03149 min-1) observed for Rhodamine-B and a 91.5% degradation rate (rate constant = 0.01749 min-1) achieved for Tetracycline. These impressive results were obtained using 0.3 g/L of the 13BOSBS photocatalyst under sunlight illumination for 120 min. Reusability studies confirmed the catalyst's impressive stability, with approximately 74.4% degradation of Rh-B maintained even after seven consecutive runs. Scavenger experiments highlighted the crucial role of •OH radicals in the photodecomposition mechanism. For the RhB dye, the 13BOSBS catalyst demonstrated remarkable 90.2% and 85% reductions in COD and TOC, respectively. The commercially available TC powder substantially reduced 84% in COD and 80% in TOC. Owing to its excellent attributes and simple synthesis method, the fabricated heterojunction holds great potential for ecosystem rehabilitation
Synthesis of CQD-Decorated ZnO Nanoflowers for Efficient Photocatalytic Remediation of Organic Pollutants
No full textA heterostructured ZnO–Carbon Quantum Dot (CQD’s) nanocomposite was successfully
synthesized with varying CQD’s loadings (5%, 10%, and 15%) to develop an efficient and reusable
photocatalyst for environmental remediation. The composite exhibited a distinctive nanoflowerlike ZnO morphology uniformly decorated with CQD’s, forming a robust heterojunction that
enhanced visible light absorption, promoted efficient charge separation, and facilitated easy
catalyst recovery. Comprehensive material characterization using XRD, FTIR, XPS, BET, PL, UVDRS, FESEM, EDS, and HR-TEM confirmed its high crystallinity, surface area, and sunlight
responsiveness. Photocatalytic performance evaluated under natural sunlight demonstrated an
impressive 97.7% degradation of methylene blue within 60 minutes, following pseudo-first-order
kinetics with a rate constant of 0.047 min⁻¹—over five times higher than commercial TiO₂-P25.
The influence of operational parameters such as pH, light source, catalyst dosage, and reactive
species was systematically assessed. The catalyst maintained high stability and reusability,
retaining 85% efficiency after six cycles. LC-MS analysis revealed intermediate degradation
products, while TOC and COD assessments confirmed substantial mineralization. Given the
environmental persistence and toxicity of methylene blue, the ZnO-CQD composite presents a
sustainable, solar-driven approach for treating dye-contaminated wastewater with high efficiency
and recyclability
Photo-Degradation of Methylene Blue Using Clay Supported V2o5-Tio2 Nano-Composites
No full textClay supported TiO2-V2O5 nano-composites were synthesised using microwave technique. Three different samples were prepared by varying the composition of V2O5 with respect to clay-TiO2. The synthesized nano-composite was analysed using X-ray diffraction, diffuse reflectance spectroscopy, Brunauer - Emmett - Teller and Transfer Electron Microscopy. Their photocatalytic activity was compared to that of clay-TiO2 and commercially available p25 by degrading methylene blue with a catalytic dose of 0.25g per litre in 20 ml (10-4 M concentration) of dye. The degradation was carried out in both UV and visible light. It was found that presence of V2O5 along with clay-TiO2 effectively enhanced the catalytic activity of clay-TiO2 and caused dye to degrade totally in both UV and visible light
Synthesis of Dual Emissive Carbon Quantum Dots for Sensing Applications
No full textCarbon quantum dots (CQDs), a new class of nano-material with unique optical property and have great potential in various applications. This work demonstrated the possibility of tuning the emission wavelength of CQDs by simply changing the acid type used during synthesis. In particular, a mixture of sulfuric and phosphoric acids were used to carbonize the same starting precursor, sucrose. This resulted in the isolation of CQDs with green (434 nm) and yellow (520 nm) emission when excited at 350 nm. Solvatochromic effects was studied systematically using photoluminescence spectra (PL) and the origin of PL shifts of the CQDs in different solvents was discussed in regard to the contribution from hydrogen bonding and dipole–dipole interactions. A turn-on/off strategy was proposed for specific recognition of melamine. Initially on the basis of energy transfer process, selectivity of the CQDs was investigated towards different cations. CQDs were found selective only for Fe3+ ions. The sensitivity of CQDs-Fe3+ ions system was also evaluated for melamine detection and found that CQDs-Fe3+ ions mixture was selective for melamine
Fabrication of LDH Supported Homogeneous & Heterogeneous Bimetallic Nanocomposites and It’s Catalytic Applications
No full textMaster of Science -ChemistryBimetallic nanoparticles that are made up of two metal elements in a particle exhibit much
higher catalytic activity than monometallic ones because of new bi-functional or synergistic
effects, so called a ligand and/or an ensemble effect. In this work, a novel homogeneous as
well as heterogeneous Au-Ag bimetallic nanocatalyst have been synthesized, supported on
layer double hydroxide (LDH) by a simple wet chemical process. The support of LDH has
reduced the size as well as capped the bimetallic nanoparticles and hence prevents the
agglomeration. The surface morphology and chemical composition of these bimetallic
nanoparticles were examined by scanning electron microscopy, transmission electron
microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. It was found that
alloyed Au–Ag bimetallic nanoparticles (40-60 nm) are formed. Moreover, catalytic activity
for 4-nitrophenol reduction was probed for this as synthesized Au-Ag bimetallic
nanoparticles with a variety of compositions. The highest activity was seen for the Au-Ag
nanoparticles prepared with Au-Ag ratio at 1:3 and the activity became 10 to 45 times higher
than the original monometallic Au or Ag nanoparticles. The rate kinetics was studied for both
homogeneous and heterogeneous system on the reduction of 4-nitrophenol and observed that
the rate of reduction was greater in case of homogenous catalysts as compared to
heterogeneous catalysts. Also, the heterogeneous catalysts were effortlessly recovered and
reused (up to 5 cycles) after completion of the reaction
Clay Supported TiO2 Nanocomposites for Photocatalytic Degradation of Volatile Organic Compounds (VOCs) and Dyes
No full textPh D ThesisThe TiO2/bentonite nanocomposites were synthesized by a simple, facile and less time consuming microwave heating method carried out at 180oC for 10 minutes. Formation of TiO2 nanoparticles on bentonite clay surface was confirmed by HRTEM with size in the range 10-20 nm. The as-obtained nanocomposites had better porosity, surface area (112 m2/g) compared to pure clays (7-20 m2/g) and commercial TiO2 (Degussa P25, Germany) (50 m2/g) which led to degradation of methylene blue dye in almost 60 minutes. TiO2/bentonite was further compared with TiO2/kunipia-F and TiO2/kaolin which were prepared under same conditions regarding photocatalytic MB and chlorobenzene degradation. The textural differences (1:1 and 2:1) between bentonite, kunipia-F and kaolin clays led to the variation in photoactivity of TiO2/clay nanocomposites. The photocatalytic activities of the nanocomposites were found to be depended on clay texture as well as optical features of clays apart from surface area. The 2:1 clays (bentonite, kunipia-F) were observed to be better support materials for TiO2 in comparison with 1:1 clay (kaolin) regarding photocatalytic degradation of methylene blue (MB) and chlorobenzene. Among the TiO2/clay nanocomposites TiO2/bentonite showed better photocatalytic activity for both MB and chlorobenzene degradation due to its high surface area and optical absorption. Different nobel metal NPs (Ag, Au, Pd, all 1% by wt.) were loaded on bentonite/TiO2 to form bentonite/M-TiO2 (M- Ag, Au and Pd) nanocomposites to study their effect on its photocatalytic activity under UV and visible light. Among the bentonite/M-TiO2 nanocomposites, bentonite/Ag-TiO2 showed the highest activity for benzaldehyde and chlorobenzene degradation under UV and visible light. Under visible light irradiation, the photocatalytic activity of bentonite/M-TiO2 was due to SPR effect of noble metal NPs, deposited on the bentonite/TiO2 surface in which the electron gets transferred to the conduction band of TiO2 from metal NPs surface. TiO2/bentonite nanocomposite was coupled with visible light active graphitic carbon nitride (g-C3N¬4) by wet impregnation process at room temperature. TiO2 nanoparticles were found to be in close proximity with g-C3N¬4 as observed from HRTEM. The g-C3N4/TiO2/bentonite nanocomposites showed better photocatalytic activity than pure g-C3N4 and g-C3N4 /bentonite due to very effective charge separation. The as-prepared nanocomposite effectively degraded (90%) reactive brilliant red dye (RBR- X3BS) in 100 minutes of time under visible light irradiation. The high activity was attributed to effective charge separation in the nanocomposite
Catalytic and Optical Application of Metal oxide and Carbon Dot Nanostructures: Effect of Morphology and Concentration
No full textThe work elaborates the basis of semiconductor photocatalysis with a precise discussion on titanium dioxide TiO<sub>2<sub>, SiO<sub>2<sub> and MnO,<sub>2<sub>. The introduction section is focused upon the synthesis , band gap tunning, surface modification, sustianable applications of carbon quantam dots (CQDs) and detailed photocatalysis mechanism by semiconductors. Moreover the research gaps, objectives and characterization techniques with specification has also been integrated. The chapter 2 signifies the synthesis of gold nanoparticles dispersed uniformly on mesoporous silica (mAu/SiO<sub>2<sub>) by homogeneous deposition–precipitation method. Silica provides support and surface area to increase catalytic activity of gold. The Au/SiO<sub>2<sub> as photocatalyst was used for the conversion of 4-Nitrophenol (4-NP) to 4- Aminophenol (4-AP). The catalytic conversion was studied by UV-Visible spectroscopy and HPLC quantification method, which shows conversion of nitro group into amino group. The chapter 3 is focused upon the detoxification of harmful dyes through non conventional catalytic processes. This chapter reveals the synthesis of gold-titania (Au/TiO<sub>2<sub>) mesoporous nanostructure and its photocatalytic performance for degradation of alizarin dye. The chapter 4 gave detailed mechanism for fabrication of solid-phase MnO<sub>2<sub> nanoparticles by surfactant template method and were exploited as the photocatalyst for the effective one-step synthesis of amides. The chapter 5 represents a facile method for the fabrication of carbon quantum dots (CQDs) and Au@CQDs, useful for the photocatalytic hydrogen generation from water. The chapter 6 presents some interesting characteristics of CQDs and their fluorescence turn on/off quenching for the detection of 6-Thioguanine (6-TG). The CQDs were fabricated by simple one-step microwave technique and used for the simultaneous reduction of Au<sup>3+<sup> to form Au<sup>0<sup>-CQD core-shell (Au@CQDs) nanocomposites. The chapter 7 illustrates a novel approach based on the methodology to “kill waste by waste”. Firstly the toxic metal like lead (Pb) ions were detected using highly fluorescence carbon quantum dots (CQDs) and after impregnated of TiO<sub>2<sub> into the same Pb-CQDs composite, it was further used for the photodegradation of harmful industrial dyes like Reactive brilliant red X-3BS (RBX), Coralene red BS (CRB) and Remazol black XP (CNB). The last chapter 8 signifies the development of novel MnO<sub>2<sub>@CQD nanocomposite (carbon dots decorated on MnO<sub>2<sub> nanorods) which was prepared by a facile one-pot hydrothermal method. These results underline the prospective application of this metal photocatalyst in water treatment
Modification of SnO2 nanotubes with g-C3N4 for superior photocatalytic degradation of toxic dye under visible light irradiations
No full textThe industrial and domestic waste water effluents from any sources include organic chemicals
and pathogens; have maximum pollutants, which can be removed before discharging into water
bodies. One of the major water contaminated pollutant has been measured as Rhodamine B. Such
pollutant is leading in surface water and groundwater. It will cause irreversible hazards to human
and aquatic life in present era. Nanotechnology plays a main role in degrading such type of
pollutant. In order to fulfill today’s requirement, we have decided to handle the eco-friendly
green synthesis of nanoparicles and its application by merging important fields like
environmental sciences, chemical sciences and biotechnology. Here our work emphasizes on the
single step synthesis of SnO2/ C3N4 nanoparticles and it was confirmed by various physicochemical characterization techniques such as UV-Visible spectroscopy, XRD, TEM, SEM and
BET surface area. This nano-composite showed the excellent photocatalytic activity that is 97 %
and making it promising photocatalysts for degradation of dyes
Study The Effect of Surfactant on The Porous Structure of Silica Monolith
No full textM ScThesisSol-gel technique was used to fabricate silica monoliths by using different ratio of cationic,
non-ionic and anionic surfactant which are used as moulds for various industrial applications.
The as synthesized silica monoliths exhibits a hierarchical pore structure with inter-connected
mesopores having pore diameter in the range 2-50nm which was confirmed by BET analysis.
Further, the specific surface area was higher for monolith which was prepared by using
cationic surfactant (C18TAB, 782.54) and the surface morphology was confirmed by SEM
analysis. The results show the improvement of higher specific surface area of monoliths with
different chain lengths of surfactants and with the increase in the surfactants concentrations
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