Optical stability of thick‐shell CdSe@ZnS/ZnS quantum dots dissolved in n‐octane in wide range of mass concentration: photoluminescence decay study

The notable photophysical characteristics of perovskite quantum dots (PQDs) (CsPbBr3) are suitable for optoelectronic devices. However, the performance of PQDs is unstable because of their surface defects. One way to address the instability is to passivate PQDs using different organic (polymers, oligomers, and dendrimers) or inorganic (ZnS, PbS) materials. In this study, we performed steady-state spectroscopic investigations to measure the photoluminescence (PL), absorption (A), transmission (T), and reflectance (R) of perovskite quantum dots (CsPbBr3) and ethylene vinyl acetate/terpene phenol (1%) (EVA-TPR (1%), or EVA) copolymer/perovskite composites in thin films with a thickness of 352 ± 5 nm. EVA is highly transparent because of its large band gap; furthermore, it is inexpensive and easy to process. However, the compatibility between PQDs and EVA should be established; therefore, a series of analyses was performed to compute parameters, such as the band gap, the coefficients of absorbance and extinction, the index of refractivity, and the dielectric constant (real and imaginary parts), from the data obtained from the above investigation. Finally, the optical conductivities of the films were studied. All these analyses showed that the EVA/PQDs were more efficient and stable both physically and optically. Hence, EVA/PQDs could become copolymer/perovskite active materials suitable for optoelectronic devices, such as solar cells and perovskite/polymer light-emitting diodes (PPLEDs).

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Formation of Carbon Quantum Dots via Hydrothermal Carbonization: Investigate the Effect of Precursors

Energies ◽

10.3390/en14040986 ◽

2021 ◽

Vol 14 (4) ◽

pp. 986

Author(s):

Md Rifat Hasan ◽

Nepu Saha ◽

Thomas Quaid ◽

M. Toufiq Reza

Keyword(s):

Quantum Dots ◽

Optical Properties ◽

Microcrystalline Cellulose ◽

Uv Light ◽

Synthesis Method ◽

Hydrothermal Carbonization ◽

Carbon Quantum Dots ◽

Medical Diagnostics ◽

Particle Size Range ◽

Wide Range

Carbon quantum dots (CQDs) are nanomaterials with a particle size range of 2 to 10 nm. CQDs have a wide range of applications such as medical diagnostics, bio-imaging, biosensors, coatings, solar cells, and photocatalysis. Although the effect of various experimental parameters, such as the synthesis method, reaction time, etc., have been investigated, the effect of different feedstocks on CQDs has not been studied yet. In this study, CQDs were synthesized from hydroxymethylfurfural, furfural, and microcrystalline cellulose via hydrothermal carbonization at 220 °C for 30 min of residence time. The produced CQDs showed green luminescence behavior under the short-wavelength UV light. Furthermore, the optical properties of CQDs were investigated using ultraviolet-visible spectroscopy and emission spectrophotometer, while the morphology and chemical bonds of CQDs were investigated using transmission electron microscopy and Fourier-transform infrared spectroscopy, respectively. Results showed that all CQDs produced from various precursors have absorption and emission properties but these optical properties are highly dependent on the type of precursor. For instance, the mean particle sizes were 6.36 ± 0.54, 5.35 ± 0.56, and 3.94 ± 0.60 nm for the synthesized CQDs from microcrystalline cellulose, hydroxymethylfurfural, and furfural, respectively, which appeared to have similar trends in emission intensities. In addition, the synthesized CQDs experienced different functionality (e.g., C=O, O-H, C-O) resulting in different absorption behavior.

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The photoluminescence decay time of self-assembled InAs quantum dots covered by InGaAs layers

Nanotechnology ◽

10.1088/0957-4484/17/23/002 ◽

2006 ◽

Vol 17 (23) ◽

pp. 5722-5725 ◽

Cited By ~ 7

Author(s):

G W Shu ◽

C K Wang ◽

J S Wang ◽

J L Shen ◽

R S Hsiao ◽

...

Keyword(s):

Quantum Dots ◽

Decay Time ◽

Inas Quantum Dots ◽

Photoluminescence Decay ◽

Self Assembled

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Multi-Quantum Dots-Embedded Silica-Encapsulated Nanoparticle-Based Lateral Flow Assay for Highly Sensitive Exosome Detection

Nanomaterials ◽

10.3390/nano11030768 ◽

2021 ◽

Vol 11 (3) ◽

pp. 768

Author(s):

Hyung-Mo Kim ◽

Chiwoo Oh ◽

Jaehyun An ◽

Seungki Baek ◽

Sungje Bock ◽

...

Keyword(s):

Quantum Dots ◽

Limit Of Detection ◽

Specific Binding ◽

Calf Serum ◽

Lateral Flow ◽

Lateral Flow Immunoassay ◽

Uniform Size ◽

Highly Sensitive ◽

Wide Range ◽

New Biomarkers

Exosomes are attracting attention as new biomarkers for monitoring the diagnosis and prognosis of certain diseases. Colorimetric-based lateral-flow assays have been previously used to detect exosomes, but these have the disadvantage of a high limit of detection. Here, we introduce a new technique to improve exosome detection. In our approach, highly bright multi-quantum dots embedded in silica-encapsulated nanoparticles (M–QD–SNs), which have uniform size and are brighter than single quantum dots, were applied to the lateral flow immunoassay method to sensitively detect exosomes. Anti-CD63 antibodies were introduced on the surface of the M–QD–SNs, and a lateral flow immunoassay with the M–QD–SNs was conducted to detect human foreskin fibroblast (HFF) exosomes. Exosome samples included a wide range of concentrations from 100 to 1000 exosomes/µL, and the detection limit of our newly designed system was 117.94 exosome/μL, which was 11 times lower than the previously reported limits. Additionally, exosomes were selectively detected relative to the negative controls, liposomes, and newborn calf serum, confirming that this method prevented non-specific binding. Thus, our study demonstrates that highly sensitive and quantitative exosome detection can be conducted quickly and accurately by using lateral immunochromatographic analysis with M–QD–SNs.

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Microplasma Band Structure Engineering in Graphene Quantum Dots for Sensitive and Wide-Range pH Sensing

ACS Applied Materials & Interfaces ◽

10.1021/acsami.1c18440 ◽

2021 ◽

Author(s):

Darwin Kurniawan ◽

Bai Amutha Anjali ◽

Owen Setiawan ◽

Kostya Ken Ostrikov ◽

Yongchul G. Chung ◽

...

Keyword(s):

Quantum Dots ◽

Band Structure ◽

Graphene Quantum Dots ◽

Ph Sensing ◽

Wide Range ◽

Structure Engineering

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Qualitative assessment of air pollution in the working area of energy-intensive materials production by nanoscale aerosols with a solid dispersed phase

Russian Journal of Occupational Health and Industrial Ecology ◽

10.31089/1026-9428-2021-61-12-828-832 ◽

2021 ◽

Vol 61 (12) ◽

pp. 828-832

Author(s):

Boris N. Filatov ◽

Natalya I. Latyshevskaya ◽

Natalya V. Krylova ◽

Irina K. Gorkina ◽

Yulya I. Velikorodnaya ◽

...

Keyword(s):

Air Pollution ◽

Mass Concentration ◽

Solid Phase ◽

Qualitative Assessment ◽

Dust Particles ◽

Dispersed Phase ◽

Forced Circulation ◽

Aluminum Powders ◽

Nanoscale Particles ◽

Wide Range

The presence of grinding, mixing, and fractionation of solid components of formulations leads to the formation of aerosols in the air of the working area with a wide range of dispersion of the solid phase - all this characterizes the organization of technological processes for the production of energy-intensive materials. The study aims to give a qualitative assessment of possible air pollution of the working area of energy-intensive materials production by nanoscale aerosols with a solid dispersed phase. The researchers carried out the sampling of the working area air and flushes from solid horizontal surfaces to produce energy-intensive materials. We carried out the sampling by forced circulation of the test air through the absorption devices of Polezhaev. Scientists used Triton TX-114 solution with a mass concentration of 2.0 mg/dm3 as an absorption medium. The researchers performed flushing from surfaces using cloth tampons moistened with Triton TX-114 solution with a mass concentration of 2.0 mg/dm3. We determined the particle sizes in the samples using NanotracULTRA (Microtrac). Scientists found aluminum and nitrocellulose particles with sizes from 36 to 102 nm in the air of the working area and flushes from horizontal surfaces. The study of the fractional composition of RDX and aluminum powders of the ASD-1 brand showed the presence of nanoscale particles in them. Nanoscale dust particles pollute the air of the working area and solid horizontal surfaces at certain stages of the production of energy-intensive materials. There are nanoscale particles in the composition of powders of some standard components of formulations. Flushes from solid horizontal surfaces are an adequate qualitative indicator of the presence of nanoaerosols in the air of the working area.

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Synthesis and Properties of Nitrogen-Doped Carbon Quantum Dots Using Lactic Acid as Carbon Source

Materials ◽

10.3390/ma15020466 ◽

2022 ◽

Vol 15 (2) ◽

pp. 466

Author(s):

Kaixin Chang ◽

Qianjin Zhu ◽

Liyan Qi ◽

Mingwei Guo ◽

Woming Gao ◽

...

Keyword(s):

Quantum Dots ◽

Lactic Acid ◽

Fluorescence Quenching ◽

Functional Groups ◽

Fluorescence Intensity ◽

Carbon Quantum Dots ◽

Nitrogen Doped ◽

Ph Values ◽

Wide Range ◽

Nitrogen Doped Carbon

Nitrogen-doped carbon quantum dots (N-CQDs) were synthesized in a one-step hydrothermal technique utilizing L-lactic acid as that of the source of carbon and ethylenediamine as that of the source of nitrogen, and were characterized using dynamic light scattering, X-ray photoelectron spectroscopy ultraviolet-visible spectrum, Fourier-transformed infrared spectrum, high-resolution transmission electron microscopy, and fluorescence spectrum. The generated N-CQDs have a spherical structure and overall diameters ranging from 1–4 nm, and their surface comprises specific functional groups such as amino, carboxyl, and hydroxyl, resulting in greater water solubility and fluorescence. The quantum yield of N-CQDs (being 46%) is significantly higher than that of the CQDs synthesized from other biomass in literatures. Its fluorescence intensity is dependent on the excitation wavelength, and N-CQDs release blue light at 365 nm under ultraviolet light. The pH values may impact the protonation of N-CQDs surface functional groups and lead to significant fluorescence quenching of N-CQDs. Therefore, the fluorescence intensity of N-CQDs is the highest at pH 7.0, but it decreases with pH as pH values being either more than or less than pH 7.0. The N-CQDs exhibit high sensitivity to Fe3+ ions, for Fe3+ ions would decrease the fluorescence intensity of N-CQDs by 99.6%, and the influence of Fe3+ ions on N-CQDs fluorescence quenching is slightly affected by other metal ions. Moreover, the fluorescence quenching efficiency of Fe3+ ions displays an obvious linear relationship to Fe3+ concentrations in a wide range of concentrations (up to 200 µM) and with a detection limit of 1.89 µM. Therefore, the generated N-CQDs may be utilized as a robust fluorescence sensor for detecting pH and Fe3+ ions.

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Carbon Based Nanodots in Early Diagnosis of Cancer

Frontiers in Chemistry ◽

10.3389/fchem.2021.669169 ◽

2021 ◽

Vol 9 ◽

Author(s):

Gurpal Singh ◽

Harinder Kaur ◽

Akanksha Sharma ◽

Joga Singh ◽

Hema Kumari Alajangi ◽

...

Keyword(s):

Quantum Dots ◽

Early Stage ◽

Imaging Techniques ◽

Graphene Quantum Dots ◽

Carbon Quantum Dots ◽

Diagnostic Methods ◽

Early Diagnosis Of Cancer ◽

Successful Treatment Outcome ◽

Wide Range ◽

Carbon Based

Detection of cancer at an early stage is one of the principal factors associated with successful treatment outcome. However, current diagnostic methods are not capable of making sensitive and robust cancer diagnosis. Nanotechnology based products exhibit unique physical, optical and electrical properties that can be useful in diagnosis. These nanotech-enabled diagnostic representatives have proved to be generally more capable and consistent; as they selectively accumulated in the tumor site due to their miniscule size. This article rotates around the conventional imaging techniques, the use of carbon based nanodots viz Carbon Quantum Dots (CQDs), Graphene Quantum Dots (GQDs), Nanodiamonds, Fullerene, and Carbon Nanotubes that have been synthesized in recent years, along with the discovery of a wide range of biomarkers to identify cancer at early stage. Early detection of cancer using nanoconstructs is anticipated to be a distinct reality in the coming years.

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