CdS Concentration Research Articles

Carbon dots induced homeotropic alignment in a negative dielectric nematic liquid crystal material

Abstract Recently, doping guest materials such as quantum dots (QDs) into liquid crystals (LCs) has been of great interest since their addition substantially enhances the properties of LC and opens new avenues for scientific advancement. Here, we report the induction of homeotropic alignment in cells without alignment layers of the negative dielectric nematic liquid crystal, N-(4-Methoxybenzylidene)-4-butylaniline (MBBA) by doping with carbon dots (CDs ∼2.8 ± 0.72 nm). The CDs-MBBA composites (CDs concentration: 0.002, 0.01, 0.03, 0.1 and 0.3 wt%) were investigated using optical polarising microscopy, electro-optical and dielectric techniques. Polarizing optical micrographs and voltage dependent optical transmission revealed the induced homeotropic alignment for all the composites under investigation. Interestingly, the least concentrated sample, 0.002 wt% exhibited partial homeotropic alignment. However, due to light leakage, the optical transmission value below threshold voltage was relatively higher than the rest of the composites. MBBA is a negative dielectric material, hence the application of a voltage across the cell was able to switch the alignment from a dark to a bright state for all composites. However, above a certain voltage (>threshold voltage), the bright state produced some instabilities. The value of dielectric permittivity was observed to decrease with increasing concentration, confirming the effect of CDs in producing homeotropic alignment in MBBA. Measurements as a function of temperature were conducted to examine the thermal stability of the induced alignment. The alignment was found to be stable throughout the nematic phase of MBBA. The induction of such alignment without conventional alignment (i.e., rubbing of polyimides) technique can be helpful in addressing the evolving display demands by making liquid crystal displays (LCDs) and other display devices cost effective.

Enhanced photocatalytic properties of TiO2/rGO nanocomposites Doped with CdS

To increase the photocatalytic activity of nanocomposite based on TiO2 and rGO (NC) and improve its photosensitivity in the visible region of the spectrum, the influence of CdS concentration (1 to 10 wt% with respect to NC) on its physicochemical and photocatalytic properties was studied. The addition of CdS to NC leads to a significant increase in the photocatalytic activity. An almost fivefold increase in photocurrent compared to pure NC was registered for NC/CdS_5%. Data on Methylene blue photodegradation showed that after 210 min of irradiation, only 5 % of dye molecules remained in solution. This value is 14.4 and 11.6 times higher than that of pure NC or CdS, respectively. Enhanced photocatalytic activity is related both to the improvement of NC absorption in the region of 400–800 nm and the decrease of the band gap width of NC upon addition of CdS, as well as the significant change in the electrophysical characteristics of the nanocomposite.

Cyclodextrin effects on the distribution, solubility and transport properties of umifenovir

The present study was initiated by an ambiguous opinion on the therapeutic efficacy of antiviral and potential anti-SARS-CoV-2 drug umifenovir (UMF). With a high degree of probability, low efficacy of UMF can be due to its poor solubility and, as follows, inefficient bioavailability after oral administration. In our investigation we aimed at improving the UMF solubility with cyclodextrins and its correlation to distribution (1-octanol/buffer and n-hexane/buffer systems) and permeability (biomimetic PermeaPad barrier). The experiments demonstrated a strong dependence of the UMF solubility and distribution parameters on the pH of the aqueous medium. The solubility of UMF was maximally increased up to 11.2-fold and 29.5-fold in HP-β-CD and SBE-β-CD solutions, respectively, with buffer pH 7.4. The distribution tests with the additions of several CDs concentrations to the buffer phase allowed to determine the intrinsic value of the distribution coefficient - the parameter important for the evaluation of the compound lipophilicity. The permeability-distribution interplay demonstrated the permeability to be mainly governed by the high lipophilicity of UMF.

Ta2O5 coatings modified with CdS, ZnO, and Dy2O3 particles prepared by plasma electrolytic oxidation of tantalum for the photocatalytic degradation of methyl orange

Ta2O5/CdS, Ta2O5/ZnO and Ta2O5/Dy2O3 coatings for application in photocatalytic degradation of methyl orange were prepared by plasma electrolytic oxidation of tantalum in an alkaline electrolyte with different concentrations of CdS, ZnO, and Dy2O3 particles up to 2.0 g/L. The coatings were characterized by SEM/EDS, XRD, Raman spectroscopy, DRS and photoluminescence spectroscopy. The morphology, thickness, phase structure and absorption properties of all coatings are almost identical and independent of the content of CdS, ZnO, and Dy2O3 embedded in Ta2O5 coatings. The orthorhombic and monoclinic phases of Ta2O5 are the main constituents of the coatings. Due to the low content of embedded CdS, ZnO, and Dy2O3 in Ta2O5 coatings, they exhibit high absorption in the middle ultraviolet region, which is characteristic of Ta2O5. The photocatalytic activity (PA) of Ta2O5/CdS, Ta2O5/ZnO and Ta2O5/Dy2O3 is higher than that of pure Ta2O5 and depends on the amount of CdS, ZnO, and Dy2O3 in the electrolyte, respectively. The highest PA was observed for coatings formed in an electrolyte containing 0.5 g/L of CdS, ZnO, and Dy2O3. The improved PA of Ta2O5/CdS, Ta2O5/ZnO and Ta2O5/Dy2O3 compared to Ta2O5 is related to the reduction of photogenerated electron/hole recombination. The mechanism of the photogenerated electron/hole transfer process is presented and discussed.

Effect of carbon dots on tuning molecular alignment, dielectric and electrical properties of a smectogenic cyanobiphenyl-based liquid crystal material

Here, we demonstrate the effect of dispersing organosoluble carbon dots (CDs, ∼7–8 nm) on tuning the molecular alignment, dielectric and electrical properties of smectic A (SmA) and nematic (N) mesophases of a thermotropic smectogenic LC material, 4-octyl-4′-cyanobiphenyl (8CB) in a planar anchored indium tin oxide (ITO) sample cell using polarized optical microscopy and dielectric spectroscopic techniques. The cross-polarized optical textures clearly show that the doping of CDs (concentration ⩾0.25 wt%) in planar anchored 8CB liquid crtstal (LC) led to the changing of its alignment from planar to vertical. Interestingly, such an induced vertical alignment remains stable throughout the SmA and N phases of the 8CB LC material. Moreover, the magnitude of the real dielectric permittivity is found to increase with increasing concentration of CDs and exhibits vertical alignment values for composites (⩾0.25 wt%). The observance of short axis molecular relaxation for composites (⩾0.25 wt%) without the application of bias field confirms again the induced vertical alignment. The accumulation of CDs at the substrate surface and their interaction with the alignment and ITO layers can be attributed as an important factor for such induced vertical alignment. The electrical conductivity of 8CB is observed to increase significantly with the addition of CDs (i.e. an increment of up to two orders of magnitude in composites compared to pure 8CB) and attributed to the lowering of viscosity and change in molecular alignment. We certainly believe that such tunable molecular alignment throughout the SmA and N phases of thermotropic smectogenic LC material (8CB) by dopant CDs could pave the way for their applications in flexible displays, biosensors, electro-optical memory and other tunable photonic devices.

Determination of the binding constants and ionic mobilities of diquat complexes with randomly sulfated cyclodextrins by affinity capillary electrophoresis.

The enantiomers of diquats (DQs), a new class of functional organic molecules, were recently separated by capillary electrophoresis (CE) with high resolution up to 11.4 within 5-7 min using randomly sulfated α-, β-, and γ-cyclodextrins (CDs) as chiral selectors. These results indicated strong interactions between dicationic diquats and multiply negatively charged sulfated CDs (S-CDs). However, the binding strength of these interactions was not quantified. For that reason, in this study, affinity CE was applied for the determination of the binding constants and ionic mobilities of the complexes of DQ P- and M-enantiomers with CD chiral selectors in an aqueous medium. The non-covalent interactions of 10 pairs of DQ enantiomers with the above CDs were investigated in a background electrolyte (BGE) composed of 22mM NaOH, 35mM H3PO4, pH 2.5, and 0.0-1.0mM concentrations of CDs. The average apparent binding constant and the average actual ionic mobility of the DQ-CD complexes were determined by nonlinear regression analysis of the dependence of the effective mobility of DQ enantiomers on the concentration of CDs in the BGE. The complexes were found to be relatively strong with the averaged apparent binding constants in the range 13600-547400 L/mol.

Green synthesis of CdS/flaxseed mucilage nanocomposite films using gamma irradiation for packaging applications

Abstract The most common ways to produce nanoparticles are through chemical and physical processes, which can be expensive and environmentally hazardous. Using plant extracts (green synthesis) as reducing and capping agents is a simple, cost-effective, and environmentally friendly method of lowering the usage of dangerous chemicals in the synthesis of metal nanoparticles. This study covers the environmentally friendly synthesis of cadmium sulphide nanoparticles (CdS NPs) using a blend of flaxseed extracts (FM), polyvinyl alcohol (PVA), and chitosan (Cs). The composites are then exposed to gamma irradiation at doses of 20 kGy and 40 kGy. UV–VIS absorption spectroscopy, SEM, HRTEM, EDX, and FTIR were used to analyse the produced nanocomposite films. UV–Vis absorption spectra showed considerable surface Plasmon resonance (SPR) bands at 396–440 nm, indicating that CdS NPs had been successfully synthesized. A progressive red shift in wavelength was noted, along with the broadening of the absorption band as the irradiation dose increased. Transmission electron microscopy pictures revealed that the generated CdS nanostructures were dispersed as spherical nanoparticles with remarkable structural homogeneity. Tensile strength and elongation measurements of the films revealed that the inclusion of CdS NPs improved their mechanical properties. The addition of CdS NPs to the current blends limits biodegradation in soil. Thermal gravimetric analysis findings showed that CdS NPs included in FM/PVA films had improved thermal stability. The antimicrobial activities of the tested films were performed against Staphylococcus aureus, Escherichia coli, and Candida albicans. The results revealed that all of the films exhibited more antibacterial activity against S. aureus than the two others, with the highest activity observed in nanocomposites with a high concentration of CdS.

Remediation of phenanthrene by highly efficient CdS–SnS photocatalyst and its cytotoxic assessments

Cadmium sulfide-tin sulfide (CdS–SnS) nanoparticles are a novel kind of photocatalyst. These CdS–SnS nanoparticles are synthesized and characterized using UV–Vis, FT-IR, XRD, SEM-EDX, and DLS techniques, to understand their size distribution, crystalline nature, morphology, shape, optical properties, and elemental composition. This research offers insight into the efficient photocatalytic degradation of Phenanthrene (PHE) using CdS–SnS. The CdS–SnS NPs as photocatalyst can effectively photodegrade the polycyclic aromatic hydrocarbons (PAH) such as phenanthrene under simulated solar and UV light. UV–vis spectra of these nanoparticles exhibit peaks at 365 and 546 cm−1 respectively, the mean size of the CdS–SnS NPs in DLS is determined to be 78 nm. The CdS–SnS stretching frequency was observed at wave numbers below 700 cm−1, the absorption peak at 1123 cm−1 indicates the presence of C–N stretch or CS bond of thiourea, while the peak at 1350.38 cm−1 corresponds to the tris-amine C–N stretch in FT-IR. Additionally, the peaks observed at 2026 cm−1 indicate the presence of isothiocyanate (NCS). 1456.23 cm−1 represents the asymmetric scissor deformation vibration. EDAX revealed the presence of elemental Cd and Sn oxides. The antimicrobial studies showed that the CdS–SnS NPs at the concentration of 150 μg/mL, exhibit maximum inhibition (15 ± 1.25 mm) against the strains Proteus mirabilis followed by Staphylococcus epidermidis and Clostridium spp. Among fungal strains Colletotrichum spp. exhibits the maximum zone of inhibition (9 ± 0.25). This research also observed the cytotoxic effects of CdS–SnS NPs on HepG2 and ZF4 cells. HepG2 cells exhibited 50% inhibition at 50 μg/mL and 70% inhibition at 100 μg/mL concentrations, while ZF4 cells exhibited 50% inhibition at 50 μg/mL and 78% inhibition at 100 μg/mL concentrations, respectively. The parameters like concentration of PHE, concentration of CdS–SnS NPs, pH, and sources of irradiation on batch adsorption were examined to maximize the efficiency of the photodegradation process.

Designing of chitosan/gelatin based nanocomposite films integrated with Vachellia nilotica gum carbon dots for smart food packaging applications

Microbial growth and exposure to UV light is a persistent global concern resulting in food spoilage, therefore, smart packaging is crucial for the availability of safer and quality food. Present work describes fabrication of chitosan (CH) and gelatin (GL) based nanocomposite films by introducing green source, highly fluorescent Vachillia nilotica gum-derived carbon dots (VNG-CDs). The VNG-CDs and incorporated CH/GL nanocomposite films were characterized by UV–Visible, FTIR, XRD, SEM and TGA analysis. The FTIR and XRD data revealed that VNG-CDs, chitosan, gelatin, and glycerol are combined/interlinked to form homogeneous nanocomposite films. The inclusion of VNG-CDs to CS/GL-CDs nanocomposite film efficiently enhanced the thermal stability and improved mechanical properties. VNG-CDs added to films markedly blocked the ultraviolet light and their effectiveness improved as concentration of CDs increases, being >90 % in UVC (200–280 nm) region. The prepared CS/GL-CDs nanocomposite films manifested radical scavenging activity, reducing capability and also excellently inhibited growth of E. coli, K. pneumonia and S. aureus bacteria. The viability of CS/GL-CDs nanocomposite films examined using banana as a model fruit extending the storage time by two weeks. In conclusion, CH/GL films containing VNG-CDs can be developed into smart packaging materials with enhanced protection and antimicrobial properties.

IN-VITRO STUDIES OF BETAMETHASONE/CYCLODEXTRIN INCLUSION COMPLEXES

The interaction of Betamethasone with different types of CDs was investigated. The effects of the types and concentration of CDs, as well as temperature on the inclusion behavior were also investigated. Different techniques were used in this investigation including PSD, DSC, SEM, 1H-NMR and MM. PSD results indicated
 that the tendency of BMTZ to bind to CDs follows the order g-CD?a-CD<HP-b-CD<b-CD. This provides indications that size fit plays an important role on the inclusion complexation process. The thermodynamic parameters of the inclusion complexes under investigation were calculated. The negative entropy change indicated that conformational changes were the dominant compared to the release of water solubility for the CD cavity and these formed an ice-burg structure around the BMTZ. MM study revealed that the dominant driving force of the inclusion complexation is the electrostatic energy. The DSC and SEM confirmed the formation of inclusion complex in the solid state.

Sensing behavior of CdS-TiO2 thick films for the detection of hydrocarbons.

In this article, the sensing behaviors of undoped titanium dioxide (TiO2) and CdS-doped TiO2 (CdS-TiO2) thick films are discussed. Sensing pastes of 2 wt% CdS-TiO2 and undoped TiO2 were prepared in the laboratory and used to fabricate thick film gas sensors on an alumina substrate. The crystal structures of TiO2 and CdS-TiO2 samples were characterized by XRD and atomic force microscopy (AFM). The results indicated that the grain size and RMS roughness parameter were reduced by adding CdS contents. The sensing behaviors of the fabricated devices were studied at varying concentrations (0-5000 ppm) of different hydrocarbon gases, such as LPG, methanol, ethanol, toluene, and benzene, in ambient air at 300 K. The effect of humidity levels on the sensing properties of the sensors was also investigated. The sensor response value of CdS-TiO2 for benzene was found to be 2.25 times higher than that of TiO2-based sensing devices. Thus, CdS doping significantly enhanced the response and recovery times of the sensor. The TiO2 film exhibited response and recovery times of 65 s and 180 s, respectively. In contrast, when doped with CdS, the response times were reduced to 15 s and 103 s, respectively, when exposed to benzene at a concentration of 5000 ppm at 300 K. The sensing mechanism has been discussed and the experimental results were validated using a model based on the Frenkel-Poole theory of electronic emission and catalytic oxidation. The obtained results demonstrate that TiO2 structures doped with low concentrations of CdS exhibit superior sensitivity and selectivity to benzene gas under low humidity levels at room temperature (300 K).

Enhancing Photodetection Performance and Thermal Tolerance of CdS Thin Films through Cobalt (Co) Doping

A visible light photodetector is developed using cobalt (Co)‐doped cadmium sulfide (CdS) thin films that exhibits outstanding characteristics with a photocurrent of 284 μA, responsivity of 13.2 A W−1, an extraordinary external quantum efficiency (EQE) of 4550%, exceptional sensitivity (2.84 × 106%), and a rapid response time of 0.6 ms. These remarkable properties are most pronounced in 1 wt% Co‐doped CdS device and decrease with higher Co doping concentrations. This enhanced performance is attributed to the introduction of a defect energy band (DEB) near the CdS valence band, supported by UV‐Vis absorption spectra with a distinct feature at 744 nm. This DEB remains fully populated at room temperature and plays a vital role in responding to temperature variations. Our investigation reveals that 1 wt% Co‐doped CdS device exhibits significant (90%) thermal tolerance compared to pure CdS (10%) and higher Co doping concentrations (20%) in the temperature range of 27–110 °C. This improved thermal stability is attributed to the optimal Co doping concentration, striking a balance between thermal and photo‐excitation processes, thereby stabilizing the photocurrent. This research offers valuable insights into Co‐doped CdS thin films, promising robust and reliable photodetection devices, particularly suitable for applications with fluctuating temperatures.

Effect of doping of organo-soluble carbon dots on ionic relaxation and conductivity of planar anchored cyanobiphenyl based nematic liquid crystal

We demonstrate here the striking effect of organo-soluble carbon dots (CDs, diameter ∼7- 8 nm) on the tunability of ionic relaxation and conductivity of the host, planar anchored thermotropic nematic liquid crystal (5CB, 4-Cyano-4′-pentylbiphenyl). The optical texture, frequency, temperature, and concentration dependent dielectric studies of pristine 5CB and CDs-5CB composites have been performed using the polarising optical microscope and high-resolution dielectric spectroscopy, respectively. The doping of 0.5 wt% CDs into planar anchored 5CB is resulted into the vertical alignment confirmed through the cross-polarised optical microscope. The doping of CDs in 5CB liquid crystal is resulted into an unprecedented faster ionic relaxation with an abatement of the ionic amplitude at room temperature. The shift in the relaxation frequency for 0.5 wt% CDs-5CB composite (induced vertical alignment) as compared to pristine 5CB (planar aligned) at 28 °C (nematic) is found to be ∼13 folds which is further increased to ∼18 folds at 38 °C (isotropic). A similar trend in the conductivity curve is also observed which further confirms the significant enhancement in conductivity value with increase in temperature and concentration of dopant CDs. The observation of enhanced ionic conductivity and faster ionic relaxation in CDs-5CB composites as compared to pristine 5CB are attributed to the complete change of planar to vertical alignment by doping of CDs on planar anchored liquid crystal sample cells. It appears that the plausible strong interaction between hydrocarbon chains of CDs and 5CB molecules through anchored substrate surfaces with increasing concentration of CDs and decrease in rotational viscosity of host 5CB with increasing temperature certainly plays a pivotal role in the tuning of ionic relaxation and conductivity in the liquid crystal sample cells. We certainly believe that our results would catalyze the cognizance of the ionic relaxation and conductivity in CDs-5CB composites and other related systems. Moreover, such composites with tunable ionic relaxation/conductivity would be certainly helpful in the fabrication of various tuneable devices such as wave front corrector, low frequency oscillation generators, dynamic light scattering, and so on.

Optical, microstructural, and magnetic hyperthermia properties of green-synthesized Fe3O4/carbon dots nanocomposites utilizing Moringa oleifera extract and watermelon rinds

Cancer therapy with targeted-localized heating is one of the breakthroughs in the biomedical field. The incorporation of magnetic nanoparticles and fluorescent nanoparticles was one of the crucial issues for magnetic hyperthermia applications. This research investigates the magnetic hyperthermia properties of green-synthesized Fe3O4/CDs. Fe3O4 nanoparticles were synthesized using the coprecipitation method with Moringa oleifera leaf extract as a reducing agent and stabilizer. In contrast, CDs were synthesized using a hydrothermal method with watermelon rind waste as a carbon source. X-ray diffraction analysis confirmed the presence of cubic inverse spinel and a reduction in crystallite size with increasing CDs concentration. Transmission electron microscopy revealed particle size distributions of 9.7 nm for Fe3O4 and 7.5 nm for Fe3O4/CDs. Scanning electron microscopy showed that CDs were distributed on the surface of Fe3O4. The detection of characteristic FeO, CC, CO, and CO-C bonds indicated the presence of CDs on the surface of Fe3O4. Ultraviolet-visible spectroscopy spectra absorption peaks at 282 nm for CDs and 193 nm for Fe3O4. Photoluminescence spectra indicated shifts from 509 to 505 nm in excitation wavelength for both CDs and Fe3O4/CDs, situated within the green region of visible light. The vibrating sample magnetometer revealed that the nanocomposites displayed characteristics of soft ferromagnetic materials. Furthermore, the specific absorption rate (SAR) value of Fe3O4/CDs was found to be dependent on magnetization. The SAR value of Fe3O4/CDs decreased as the concentration of CDs increased, and the frequency and strength of the AMF increased. Therefore, these results can promote Fe3O4/CDs nanocomposites as a promising candidate for magnetic hyperthermia applications.

Photocatalytic, electrical, and magnetic properties of carbon dots/hexaferrite's composites

The Y-type hexaferrite and its nanocomposite with carbon dots have been made by using a hydrothermal approach, whereas BaSrZn2-xMnxFe12-2ySiyNiyO22 (x = 0.0, 0.25, 0.5, 0.75, and 1.0) was made using a conventional microemulsion process. A variety of approaches are used to explore the structural features, surface area, and morphology of the materials. As indicated by on-site substitutions and super-exchange interaction, saturation magnetization (Ms) and magnetic remanence (Mr) rise from 18 to 6 to 47.4 emu g−1 and 6.7–18.3 emu g−1, respectively with x,y = 0.75, although coercivity (Hc) declines from 1.4 to 0.39 kOe. The ferrite material's electrical resistivity enhanced from 25.85 × 106 to 49.13 × 106 Ω-cm. The increased saturation magnetization (Ms), magnetic remanence (Mr), and electrical resistance of ferrite material make it suitable for both high-density recording and microwave devices. The photocatalyst (composite) for the degradation of Rhodamine B in the presence of visible light was made from SrBaZn1.25Mn0.75Fe10.5Si0.75Ni0.75O22/CDs with different ratios. Photocatalysts with a modest CDs concentration (2.5 wt%) successfully degraded Rhodamine B (RhB) up to 94%. After eight rounds, the composite showed excellent structural stability and good reusability. The trapping experiments confirmed that OH radical species are the major contributor in the degradation process. The composite material could be used to catch visible light and purify the environment from various pollutants in the future.

Eco-friendly carbon dots induced thermally stable vertical alignment in planar anchored nematic liquid crystal

We report the induction of thermally stable vertical alignment of nematic liquid crystal, 4-cyano-4′-pentylbiphenyl (5CB), in a planar anchored cell by doping with eco-friendly carbon dots (CDs, diameter ∼7–8 nm), investigated through thermal, optical, electro-optical and dielectric spectroscopic techniques. Cross-polarized optical textures and voltage-dependent optical transmission measurements demonstrate the induction of vertical alignment of CDs-5CB composites with concentration of CDs (≥0.3 wt%) in planar anchored sample cells at room temperature. Moreover, the frequency-bias-concentration dependent dielectric studies done also confirms the induced vertical alignment. For instance, the relative dielectric permittivity measured on CDs-5CB composites (CDs ≥ 0.3 wt%) in planar anchored sample cells at bias voltage of 0 V and 30 V DC are almost equal and the presence of a short axis molecular relaxation at 0 V confirms the induced vertical alignment. The concentration and bias dependence of short axis molecular relaxation frequency are also discussed. It appears that CDs are able to align 5CB molecules vertically at the substrate by overcoming the pre-existing planar anchoring. Such induced alignment would propagate through the bulk of sample cell because of the coherence length of nematic liquid crystal molecules and eventually the whole sample obtains vertical alignment. We anticipate the great utility of these composites in the production of eco-friendly liquid crystal displays and other photonic devices, sensors, etc.

Hijacking the hydrogen atoms in photo-splitting of H2O2 for efficient reduction of CO2 to CH3OH

Photo-splitting of H2O2 in visible light is achieved by Cu-MOFs of Cu nodes and 1, 3, 5-benzene tricarboxylic acid (BTC) organic linkers (CuM) decorated with CdS (C) at varying concentrations of CdS in the CuMC composite. This process produces abundant nascent hydrogen atoms to promote the efficient catalytic reduction of CO2 to methanol (CH3OH) in visible light. The slow rate of recombination of the nascent hydrogen atoms produced by the H2O2 photo-splitting on the surface of the CdS quantum dots ensures a high steady-state concentration of hydrogen atoms with significantly reduced production of the less reactive hydrogen gas. With slow recombination of the photo-generated charges and the large surface areas for CO2 adsorption by the MOF, one of the CuMC composites is capable of convertingCO2 into CH3OH with a quantum efficiency approaching 80 %. A mechanism for the selective conversion of CO2 into CH3OH is proposed.

Nd3+ high order electrical susceptibility induced by CdS nanocrystals in a phosphate glass matrix

In this work the nonlinear optical properties of a phosphate glass matrix doped with Nd3+and codoped with CdS nanocrystals have been investigated by the time-resolved Z-scan technique. Analyzing the transient signal, it was possible to discriminate the thermal effect from the populational effects on the nonlinear refraction and absorption, allowing the determination of the parameters n2’, n2” and n4’. The dependence of these parameters on the relative concentration of Nd and CdS was also investigated, and a linear increase of these parameters with the CdS absorption was observed. Evidence of energy transfer between Nd and CdS nanocrystals was investigated by the determination of the non-radiative decay rate through lifetime measurements monitoring the emission at 1064 nm referring to the transition 4F3/2⟶ 4I11/2 of the Nd3+.

Selective and sensitive electrochemical detection of doxorubicin via a novel magnesium oxide/carbon dot nanocomposite based sensor

In the present study, we prepared novel and multifunctional carbon dots/magnesium oxide (CDs/MgO) nanocomposites with varied amount of CDs (0.5–5 wt%) via a facile hydrothermal process. The nanocomposites were then utilized for the fabrication of CDs/MgO-modified screen printed carbon electrodes (CDs/MgO/SPCE) for highly sensitive and selective electrochemical detection of the anticancer drug doxorubicin (DOX) using cyclic voltammetry. All the prepared CDs/MgO nanocomposites possess excellent efficiency towards the electrochemical oxidation of the DOX at the surface of SPCE by facilitating electron transfer reaction with increasing concentration of CDs in comparison with bare MgO nanoparticles (NPs) and CDs due to increased electroactive surface area. Besides, the oxidation peak current was also found to be increased with increasing scan rate from 50 to 150 mV/s−1. The CDs-5.0/MgO nanocomposite exhibited maximum oxidation response for the detection of DOX (10 µM) at pH 5 and at a scan rate of 50 mV/s−1. Under the optimized conditions, CDs-5.0/MgO modified SPCE exhibited a linear response for the determination of DOX in the concentration range of 0.1–1 µM (correlation coefficient, R2 = 0.99) with a low detection limit of 0.09 µM. Furthermore, a negligible effect of the common interfering agents validated the superior selectivity of the sensor (CDs-5.0/MgO/SPCE) towards DOX. The suitable linear range, low detection limit, rapid response, and excellent sensitivity of the proposed sensor (CDs/MgO/SPCE) make it a promising tool for the determination of DOX in biological, clinical, and pharmaceutical fields.

Regulation mechanism of human insulin fibrillation by L-lysine carbon dots: low concentration accelerates but high concentration inhibits the fibrillation process.

The fibrillation process of human insulin (HI) is closely related to the therapy for type II diabetes (T2D). Due to changes in the spatial structure of HI, the fibrillation process of HI takes place in the body, which leads to a significant decrease in normal insulin levels. L-Lysine CDs with a size of around 5 nm were synthesized and used to adjust and control the fibrillation process of HI. ThT fluorescence analysis and transmission electron microscopy (TEM) characterization of the CDs showed the role of HI fibrillation from the perspective of the kinetics of HI fibrillation and regulation. Isothermal titration calorimetry (ITC) was used to explore the regulatory mechanism of CDs at all stages of HI fibrillation from the perspective of thermodynamics. Contrary to common sense, when the concentration of CDs is less than 1/50 of the HI, CDs will promote the growth of fibres, while a high concentration of CDs will inhibit the growth of fibres. The experimental results of ITC clearly prove that different concentrations of CDs will correspond to different pathways of the combination between CDs and HI. CDs have a strong ability to combine with HI during the lag time, and the degree of combination has become the main factor influencing the fibrillation process.