Synthesis Of SnO2 Quantum Dots Research Articles

Sustainable green synthesis of SnO2 quantum dots: A stable, phase-pure and highly efficient photocatalyst for degradation of toxic dyes

A facile, scalable, green, convenient, high yield and environmentally sustainable strategy has been devised to synthesize SnO2 quantum dots as fine amorphous powder using an aqueous extract of edible and abundantly available marine alga, Ulva sp. The phytochemicals present in the alga have served as capping and stabilizing agent in the synthesis. The structure, morphology, optical properties and chemical oxidation state of the materials were investigated by UV–Vis, FT-IR, Raman, XRD, XPS, TEM, SEM, EDAX and BET techniques. The size of as-synthesized SnO2 nanoparticles were <5 nm indicating the formation of quantum dots (QDs). Retrievable and reusable, the as prepared SnO2 QDs served as highly efficient photocatalyst for fast degradation of water soluble toxic dyes viz., methylene blue (MB), methyl orange (MO) and rhodamine B (RhB) individually, also their binary mixtures, MB-MO, MB-RhB and ternary mixtures MB-MO-RhB under naturally available scattered sunlight. A significant reduction in total organic carbon (TOC) by the SnO2 QDs catalyst suggests that it efficiently converted MB, MO, and RhB dyes into less harmful intermediate products or directly into CO2 and H2O, making them environmentally benign. The catalytic performances of the newly prepared material were assessed to be much higher than several reported SnO2 or metal doped SnO2 nanomaterials. The as-synthesized SnO2 QDs photocatalyst could be recovered reused for at least five consecutive catalytic cycles without any decline in efficiency indicating the high stability of the photocatalyst.

Comparative Study of Sonophotocatalytic, Photocatalytic, and Catalytic Activities of Magnesium and Chitosan-Doped Tin Oxide Quantum Dots.

The present study demonstrates the hydrothermal synthesis of SnO2 quantum dots (QDs) doped with different concentrations (2, 4 wt %) of magnesium (Mg) and a fixed amount of chitosan (CS). The obtained samples were investigated through a number of characterizations for optical analysis, elemental composition, crystal structure, functional group presence, interlayer spacing, and surface morphology. The XRD spectrum revealed the tetragonal structure of SnO2 with no significant variations occurring upon the addition of CS and Mg. The crystallite size of QDs was reduced by incorporation of dopants. The optical absorption spectra revealed a red shift, assigned to the reduction of the band gap energy upon doping. TEM analysis proved that the few nanorod-like structures of CS overlapped with SnO2 QDs, and agglomeration was observed upon Mg doping. The incorporation of dopants little enhanced the d-spacing of SnO2 QDs. Moreover, the synthesized nanocatalyst was utilized to calculate the degradation percentage of methylene blue (MB) dye. Afterward, a comparative analysis of catalytic activity, photocatalytic activity, and sonophotocatalytic activity was carried out. Notably, 4% Mg/CS-doped QDs showed maximum sonophotocatalytic degradation of MB in basic medium compared to other activities. Lastly, the prepared nanocatalyst was found to be efficient for dye degradation in any environment and inexpensive.

A sensitive humidity sensor at low pressure with SnO2 QDs

The humidity sensor working at low pressure has importance in fruit processing industries, space applications, and vacuum coatings. So, it is imperative to develop a sensor to measure very low levels of humidity in a vacuum domain. In the present work, a resistive humidity sensor made of SnO 2 Quantum Dots(QDs) is demonstrated. The huge surface area (160 m 2 /g) of QDs provides plenty of oxygen vacancies at the surfaces which help to absorb moisture even at a low pressure of ~5 mbar starting from the atmospheric pressure. These QDs characterized by XRD, TEM, and optical spectroscopic techniques reveal structural details including the presence of vacancies. The performance of the QDs sensor due to the humidity effect is further proved by flow dry N 2 flow. The role of surface hydroxyl groups and their tie-in with RH sensing with high reproducibility performance under vacuum are exclusively highlighted for the first time with SnO 2 QDs at room temperature. • Surfactant free synthesis of SnO2 quantum dots. • Huge specific area and surface defects creation for adsorption of moisture. • Room temperature humidity sensor performing even at low pressure of ~ 5 mbar. • Spectroscopic evidences of surface hydroxyl and H+ mediated resistive mechanism for humidity sensor.

Synthesis of Sno2 Quantum Dots Sensitized Lafeo3 for Formic Acid Gas Sensing Properties

Synthesis of Sno2 Quantum Dots Sensitized Lafeo3 for Formic Acid Gas Sensing Properties

Mo-modified band structure and enhanced photocatalytic properties of tin oxide quantum dots for visible-light driven degradation of antibiotic contaminants

Functional nanomaterials are desirable in the sustainable photocatalytic degradation of antibiotic contaminants, but the development of nanostructured photocatalysts is facing fatal challenges not only in synthesis strategies but also in property control. Herein, a facile synthesis strategy is accomplished by the green synthesis of SnO2 quantum dots (QDs) engineered by Mo modification. The effects of Mo incorporation on the microstructural, compositional, electrical and optical properties are discussed. The electronic band structure of SnO2 QDs is modified by Mo dopants, which reduce the band gap by changing the position of the conduction band edge. The Mo-modified band structure provides the SnO2 QDs with visible-light driven photocatalytic abilities in the removal of antibiotics as emerging organic contaminants. The nanostructured photocatalysts exhibit proficient performances in the degradation of tetracycline hydrochloride. The degradation efficiency is up to 96.5% when the antibiotic concentration is 25 mg/L and the rate constant is 0.033 min−1. The hydroxyl radicals, produced by the oxidation of water, are determined to be the main active species in the photocatalytic process. The valence band edge over 3 eV guarantees the strong oxidizing abilities of photogenerated holes to create highly active hydroxyl radicals for the efficient photocatalytic degradation. First principle calculations based on the density functional theory reveal the mechanism of Mo modification, illustrating that Mo 4d electrons extend the conduction band edge to the Fermi level. The present work provides a green synthesis strategy and mechanism insights for band structure modification of SnO2 QDs as proficient visible-light driven photocatalysts for environmental remediation.

Electrochemiluminescence aptasensor for lincomycin antigen detection by using a SnO2/chitosan/g-C3N4 nanocomposite

In this paper, hydrothermal method was used for the synthesis of SnO2 quantum dots (QDs). The prepared SnO2 QDs have a uniform particle size distribution and good electrochemiluminescence (ECL) property. Then the prepared SnO2 QDs was combined with graphene-like carbon nitride (g-C3N4) through chitosan to form SnO2/chitosan/g-C3N4 nanocomposite and used for detecting the lincomycin. The characteristics of SnO2/chitosan/g-C3N4 nanocomposite were presented by transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), and the analytical results proving that the nanocomposite was prepared successfully. In this strategy, the SnO2/chitosan/g-C3N4 nanocomposite was acted as the substrate of aptasensor. Then, SH-DNA (aptamer DNA) was assembled on the surface of electrode, after 6-mercaptohexanol (MCH) blocked the unbound sites of the electrode surface, ferrocene-DNA (Fc-DNA) was incubated on the electrode surface through base complementation with aptamer DNA. In the absence of lincomycin, due to the low conductivity of Fc-DNA and the photo-excited energy electron transfer, the ECL signal was quenched. In the presence of lincomycin, the aptamer DNA was specific binding with lincomycin, and ferrocene-DNA (Fc-DNA) was detached from the surface of aptasensor electrode, generating an obviously enhancement of ECL signal. To ensure the accuracy of the data, each electrode runs continuously for 3600 s. Under optimal experimental conditions, the detection range of the aptasensor was 0.10 ng mL−1 - 0.10 mg mL−1, and the detection limit was 0.028 ng mL−1. In addition, the aptasensor has good stability and reproducibility, and also provided a hopeful device for all kinds of other protein target.

Facile hydrothermal synthesis of SnO2 quantum dots with enhanced photocatalytic degradation activity: Role of surface modification with chloroacetic acid

Designing high-performance noble-metal-free photocatalysts is the key for photocatalytic technology to expand its further application in energy and environment fields. Herein, chloroacetic acid (CA) modified SnO2 quantum dots (QDs) with enhanced photocatalytic activity were prepared under hydrothermal conditions. Through XRD, TEM, FT-IR XPS, Raman and TG analysis, it was found that CA molecules were successfully linked to the surface of SnO2 QDs and formed stable SnO2@CA QDs. The SnO2@CA QDs show excellent photocatalytic activities for methyl orange, methylene blue and phenol. The photocatalytic degradation of methyl orange follows the first order reaction. From the apparent rate constant, it can be seen that the photocatalytic performances of SnO2 QDs were significantly improved by the modification of CA, while decreased with the increase of hydrothermal reaction time. Finally, the preliminary hypothesis of SnO2@CA QDs for degradation of organic pollutants has been proposed. The findings reported here could benefit the designing of highly efficient photocatalyst.

Biogenic synthesis of SnO2 quantum dots encapsulated carbon nanoflakes: An efficient integrated photocatalytic adsorbent for the removal of bisphenol A from aqueous solution

The present study investigated the decontamination of bisphenol A (BPA) from water through the coupled adsorption-photodegradation process. A biogenic synthetic route for the fabrication of novel SnO2 quantum dot encapsulated carbon nanoflake (SnO2–CNF) as an integrated photocatalytic adsorbent (IPCA) has been proposed and characterized with sophisticated analytical techniques. The synergistic effect of SnO2–CNF nanocomposite for the removal of BPA has been established through detailed study of integrated adsorption-photodegradation process. The Langmuir adsorption capacity was found to be 250 mg/g which is ∼1.7 and ∼5.3 times higher than that of bare CNF and bare SnO2 respectively. The overall removal efficiency through the coupled adsorption-photodegradation process has also been found to be synergistically superior (∼98%) to CNF (∼72%) and SnO2 (∼46%). The removal process of BPA has been extensively studied using adsorption kinetics model, adsorption isotherm models, and photodegradation kinetics studies. The effect of pH and multiple cycles of utilization on the overall removal efficiency have also been investigated. Both hydrogen bonding and π- π interaction might be responsible for the efficient adsorption of bisphenol A over SnO2–CNF adsorbent. The electron-hole generation of SnO2 under UV illumination coupled with electron sinking ability of CNF might as well facilitate superior photocatalytic efficiency.

Facile and fast synthesis of SnO2 quantum dots for high performance solid-state asymmetric supercapacitor

Herein, we demonstrate a facile microwave-assisted hydrothermal synthesis of SnO2 quantum dots as an active electrode material for supercapacitor applications. The SnO2 quantum dots were synthesized at 180 °C for 30 min by varying the ratio of ethanol and water (H2O) mixture. The as-synthesized SnO2 quantum dots were found to be tetragonal rutile structures with average particle size diameter 4–6 nm. The BET analysis with an optimized solvent ratio (10:30) was found to be highest surface area of 285.5 m2/g and shows pseudocapacitive behaviour with a specific capacitance of 315 F/g at a current density of 1 A/g in a three-electrode system. In addition, all solid state asymmetric supercapacitor (ASC) device was fabricated and it exhibits excellent energy density of 62 Wh/kg at power density 1 kW/kg.

Synthesis of SnO2 quantum dots by chemical precipitation assisted by ultrasound

SnO2 quantum dots were successfully prepared via chemical precipitation assisted by ultrasound. X-ray diffraction analysis confirmed the rutile tetragonal structure of SnO2 QDs with a crystallite size of 1.4 nm. The SEM micrographs of the obtained powder exhibited that the SnO2 QDs are agglomerated particles of around 10 nm, while TEM images confirmed that the crystallite size are similar to the measured from XRD. The band-gap energy of the SnO2 QDs measured from the UV–Vis reflectance spectrum of the SnO2 QDs was 4.3 eV, displaying a significantly blue-shifting attributed to quantum confinement.

Green synthesis of SnO2 quantum dots using Parkia speciosa Hassk pods extract for the evaluation of anti-oxidant and photocatalytic properties

In the present study, microwave heating method was established for the biosynthesis of SnO2 Quantum dots (QDs) using Parkia speciosa Hassk pods extract. The as-synthesized quantum dots have been characterized by various techniques such as UV, XRD, EDX, TEM, HRTEM, SAED and FTIR spectroscopy. The biosynthesized SnO2 QDs was employed for the first time as an efficient photocatalyst for the degradation of a food dye, acid yellow 23 dye from aqueous phase under the UV254 light. Various parameters, such as the effect of catalyst dose, the initial concentration of acid yellow 23 dye (AY23), pH of the solution and irradiation time on the photodegradation process are also studied for efficient and better use of the synthesized SnO2 QDs as a catalyst. The biosynthesized SnO2 QDs exhibited excellent photocatalytic performances with degradation efficiency 98% on the degradation of an aqueous solution of AY23 of concentration 5 mg/L with a catalyst dose of 20 mg under UV254 light within 24 min. The synthesized SnO2 QDs can be reused up to 5 cycles of photodegradation experiment without losing its stability and efficiency. The biosynthesized SnO2 QDs also shows a fair activity in the scavenging of 2,2-diphenyl-1-picrylhydrazyl free radical with the IC50 value of 312.6 ± 0.025 μg/mL.

Size-controlled synthesis of SnO2 quantum dots and their gas-sensing performance

Tin dioxide quantum dots (TQDs) with controllable size were synthesized by changing the amount of alkaline reagent in the hydrothermal process. The gas-sensing properties were investigated by operating chemoresistor type sensor. The morphology and structure were characterized by X-ray diffraction, scanning/transmission electron microscopy, UV–vis and Raman spectrometry. The as-synthesized SnO2 shows the characteristics of quantum dots and the narrowest size distribution is about 2–3nm. The gas-sensing results indicate that the responses are strongly dependent on the size of quantum dots. TQDs with different sizes exhibit different sensitivities and selectivities to volatile toxic chemicals such as aldehyde, acetone, methanol, ethanol and amine. Especially, when the sensors are exposed to 100ppm triethylamine (TEA), the sensing response value of TQDs with small size is two times higher than that of the large-size TQDs. The maximum response values of TQDs to 1ppm and 100ppm TEA are 15 and 153, respectively. The response time is 1s and the recovery time is 47s upon exposure to 1ppm TEA. The results suggest that it is an effective method by regulating the size of SnO2 quantum dots to detect low-concentration hazardous volatile compounds.

A novel and green process for the production of tin oxide quantum dots and its application as a photocatalyst for the degradation of dyes from aqueous phase

Green synthesis of SnO2 quantum dots (QDs) was developed by microwave heating method using the amino acids, namely, aspartic and glutamic acid. This method resulted in the formation of spherical SnO2 quantum dots with an average diameter less than the exciton Bohr radius of SnO2. The average diameter of SnO2 quantum dots formed using glutamic acid is ∼1.6nm and is smaller than that formed using aspartic acid (∼2.6nm). In the electronic spectra, a clear blue shift in the band gap energy from 4.33 to 4.4eV is observed with a decrease in particle size (2.6–1.6nm) due to three dimensional quantum confinement effects. The synthesized SnO2 QDs were characterized by transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD) and Fourier transformed infrared spectroscopy (FT-IR). The optical properties were investigated using UV–visible spectroscopy. The synthesized SnO2 QDs act as an efficient photocatalyst in the degradation of Rose Bengal and Eosin Y dye under direct sunlight. For the first time, Rose Bengal dye was degraded using SnO2 QDs as a photocatalyst by solar irradiation.

Facile synthesis of SnO2 quantum dots and its photocatalytic activity in the degradation of eosin Y dye: A green approach

Abstract A facile and green synthesis of SnO 2 quantum dots (QDs) was developed by microwave heating method using an aminoacid, serine. The method resulted in the formation of SnO 2 QDs having an average diameter of ~4.0 nm. The synthesized SnO 2 QDs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and Fourier transformed infrared spectroscopy (FT-IR). The optical properties were investigated using UV-visible spectroscopy and a clear blue shift is observed in the band gap energy (~4.5 eV) of synthesized SnO 2 QDs. These SnO 2 QDs were employed as photocatalyst in the degradation of an organic dye eosin Y by solar irradiation for the first time.

Microwave assisted fast and facile synthesis of SnO2 quantum dots and their printing applications

An efficient synthesis of highly crystalline SnO(2) QDs with a narrow size distribution (4.27 +/- 0.67 nm) was achieved by microwave-assisted decomposition of Sn(OtBu)(4) in ionic liquid. Printed structures fabricated from SnO(2) QDs showed typical semiconducting I-V behaviors, and gas sensing properties.