As-synthesized CdS Research Articles

Novel fluorescent probes based on sulfur and nitrogen co-doped carbon dots for determination of three N-substituted phenothiazine derivatives in dosage forms

In the current work, sulfur and nitrogen co-doped carbon dots (S,N-CDs) as simple, sensitive, and selective turn-off fluorescent nanosensors were utilized for analysis of three phenothiazine derivatives, including acetophenazine (APZ), chlorpromazine (CPH), and promethazine (PZH). S,N-CDs were synthesized through a green one-pot microwave-assisted technique using widely available precursors (thiourea and ascorbic acid). HRTEM, EDX, FTIR spectroscopy, UV–Vis absorption spectroscopy, and fluorescence spectroscopy were used to characterize the as-synthesized CDs. When excited at 330 nm, the carbon dots produced a maximum emission peak at 410 nm. The cited drugs statically quenched the S,N-CDs fluorescence as revealed by the Stern-Volmer equation. The current method represents the first spectrofluorimetric approach for the determination of the studied drugs without the need for chemical derivatization or harsh reaction conditions. The importance of the proposed work is magnified as the cited drugs do not have any fluorescent properties. The fluorescence of the developed sensor exhibited a linear response to APZ, CPH, and PZH in the concentration ranges of 5.0–100.0, 10.0–100.0, and 10.0–200.0 μM with detection limits of 1.53, 1.66, and 2.47 μM, respectively. The developed fluorescent probes have the advantages of rapidity and selectivity for APZ, CPH, and PZH analysis in tablets with acceptable % recoveries of (98.06–101.66 %). Evaluation of the method's greenness was performed using the Complementary Green Analytical Procedure Index (ComplexGAPI) and Analytical GREEnness metric (AGREE) metrics, indicating that the method is environmentally friendly. Validation of the proposed method was performed according to ICHQ2 (R1) guidelines.

Optical and temperature-dependent electrical and dielectric properties of ultrasound-synthesized CdS quantum dots

CdS quantum dots (QDs) were synthesized by the ultrasound-assisted chemical precipitation technique. The structure analysis revealed the presence of bi-structural cubic and hexagonal phases with an average crystallite size of 3 nm. The N2-adsorption isotherm exhibited the evolution of meso-/macro-porous interfaces with a pore size of 7.56 nm and a surface area of 44.41 m2·g−1. The improvement of the quantum size effect in CdS QDs resulted in the increase of optical bandgap to 2.52 eV compared with the corresponding bulk phase. However, the analysis of long-tail states absorption revealed a very small Urbach energy of about 76 meV compared with CdS QDs prepared by other techniques. The as-synthesized CdS QDs revealed high room-temperature DC conductivity of 2.56 × 10–6 Ω−1 · m−1 and very small activation energy of 268 meV facilitating tunnelling of the thermionically excited carrier through the high bandgap of CdS QDs. The frequency-dependent behavior of AC conductivity (σ AC) and dielectric constant (ε r) of CdS QDs were investigated at different temperatures in the range from 303 K to 453 K. It was observed that both σ AC and ε r were improved with increasing temperature up to 363 K followed by a sudden decrease at higher temperatures.

One-pot synthesis of CdS nanoparticles with surface-phase junctions to catalyze the photo-reduction of CO2 into CO and CH4 selectively

Without any external template & surfactant, CdS nanoparticles (NPs) with surface-phase junctions were synthesized directly from CdCl2 and the CS2-storage material (CS2SM) with a simple one-pot strategy, in which only stirring was needed. Under visible light irradiation, the as-synthesized CdS NPs could selectively catalyze the reduction of CO2 to produce CO and CH4 sustainably with a perfect catalyst stability even after 33 h. At 4 °C and the optical power density of 370 mW/cm2, the as-synthesized CdS NPs from 0.5 g CS2SM exhibited 195.41 μmol/gcat CH4 generation capacity and the 9.01 μmol·gcat−1·h−1 maximum average yield, in which the generation ratio of CH4/CO was at 8:2; and the as-synthesized CdS NPs from 2.0 g CS2SM exhibited 119.95 μmol/gcat CO generation capacity and the 3.75 μmol·gcat−1·h−1 maximum average yield, in which the generation ratio of CH4/CO was at 1:3. The research results indicated that CdS NPs with higher hexagonal content and smaller particle size is more active in CO2 photoreduction, which may be due to the low potential CdS NPs surface phase junction reducing the recombination rate of electron hole pairs and improving photocatalytic activity. The simple preparation of CdS NPs and their further photocatalytic CO2 reduction provide a green and sustainable foundation for the application of sulfide photocatalysts.

Detection of oxytetracycline in milk using a novel carbon dots-based fluorescence probe via facile pyrolysis synthesis.

Amphiphilic blue-fluorescence carbon dots (B-CDs) were synthesized via pyrolysis method with citric acid and oleamine as precursors. B-CDs are monodispersed in ethanol, toluene, and ultrapure water with the average particle sizes of 3.33nm, 2.05nm, and 4.12nm, respectively. The maximum emission wavelength of the B-CDs excitation at 370nm is located at 459nm. The B-CDs have good optical properties with excellent photostability. The fluorescence quantum yield (QY) of the as-prepared CDs is as high as 30.17%. The fluorescence of B-CDs is quenched because of static quenching by oxytetracycline. A high selective and sensitive fluorescence probe for detecting oxytetracycline was constructed with a linear range of 1.52-27.60µg/mL and the detection limit of 0.33µg/mL. The B-CDs-based fluorescence probe can be applied to analyze oxytetracycline in milk; the recoveries and relative standard are satisfactory. Furthermore, the B-CDs were exploited for imaging of SH-SY5Y cells. The results demonstrate that as-synthesized CDs can serve as a cellular imaging reagent owing to remarkable bioimaging performance. This work provides a new strategy for the detection of oxytetracycline in food.

Microinjection titration synthesis of CdS nano-particles with S-type interface-phase junctions for efficient photocatalytic degradation of rhodamine B

Currently, water scarcity caused by pollution is a serious threat to human survival and development. To address this problem, impurity energy levels of -NH2 groups using CS2-storage material (CS2SM) as an S source were introduced in this study, and CdS nano-particles (NPs) with enhanced sulfur vacancies (Vs-CdS NPs) and S-type interface-phase junctions were synthesized through a simple microinjection titration strategy. Moreover, rhodamine B (Rh B) with a volume of 100 mL and a concentration of 100 mg/L could be 99.7% degraded over 60 min using 20 mg of CdS NPs at pH = 6.0, T = 28 °C, and 300 W xenon lamp (optical power of 150 mW) irradiation. The high photocatalytic activity of the as-synthesized CdS NPs is owing to the intrinsic electric field, energy band bending, and Coulomb forces that occur between the hexagonal and cubic phases. In addition, the presence of Vs-CdS NPs can easily capture the photogenerated carriers of CdS NPs during recombination. Moreover, the photogenerated carriers are affected by the high and low energies between the Vs-CdS NPs, resulting in the transfer of the photogenerated carriers between the Vs-CdS NPs, which ultimately prolongs the lifetime of photogenerated carriers in the CdS NPs. Subsequently, a photocatalytic mechanism of S-type interface-phase junctions was proposed to explain the highly efficient photocatalytic activity and excellent optoelectronic properties of CdS NPs.

Photodegradation of crystal violet dye in water using octadecylamine-capped CdS nanoparticles synthesized from Cd(II) N,N′-diarylformamidine dithiocarbamates and their 2,2-bipyridine adducts

Cadmium(II) complexes of N,N′-diarylformamidine dithiocarbamate of the general formula [Cd-(L)2] (L = N,N'-bis(2,6-dimethylphenyl)formamidine dithiocarbamate L1 (1), N,N'-bis(2,6-disopropylphenyl)formamidine dithiocarbamate L2 (2), N'-(2,6-dichlorophenyl-N-(2,6-dimethylphenyl)formamidine dithiocarbamate L3 (3), N'-(2,6-dichlorophenyl)-N-(2,6-diisopropylphenyl)formamidine dithiocarbamate L4 (4) and their 2,2-bipyridine (bipy) adducts, [Cd-(L1)2bipy] (5), [Cd-(L2)2bipy] (6), [Cd-(L3)2bipy] (7), [Cd-(L4)2bipy] (8)) have been synthesized and characterized using various spectroscopic and analytical techniques. For one of the 2,2-bipyridine adducts, the molecular structure was determined using single crystal X-ray structure as a six-coordinate Cd(II) complex in which two pairs of sulfur atoms from two dithiocarbamate ligands and a pair of nitrogen atoms from bipy completed the distorted octahedral geometry. Complexes 1, 3 and 5 were used as single source precursors for formation of octadecylamine capped cadmium nanoparticles, CdS1, CdS3 and CdS5. HR-TEM images of as-synthesized CdS1, CdS3 and CdS5 particles are nano-spherical in shape with size distributions ranging between 4 and 9 nm. The as-synthesized CdS nanoparticles were used as photocatalysts for degradation of crystal violet, with degradation efficiency of 75-84% and rate constants of 0.0050, 0.0043 and 0.0039 min−1 for CdS1, CdS3 and CdS5, respectively.

Biotemplated CdS Nano-Aggregate Networks for Highly Effective Visible-Light Photocatalytic Hydrogen Production.

In the last few decades, many new synthesis techniques have been developed in order to obtain an effective visible-light responsive photocatalyst for hydrogen production by water splitting. Among these new approaches, the biotemplated synthesis method has aroused much attention because of its unique advantages in preparing materials with special morphology and structure. In this work, Hydrilla verticillata (L. f.) Royle was used as a biotemplate to synthesize a CdS photocatalyst. The as-synthesized sample had the microstructure of nano-scaled aggregate networks and its activity for photocatalytic hydrogen production was six times higher than that of CdS synthesized without a template in an Na2S-Na2SO3 sacrificial system. The use of Pt and PdS as cocatalysts further improved the hydrogen production rate to 14.86 mmol/g·h under visible-light (λ ≥ 420 nm) irradiation, so the hydrogen production can be directly observed by the naked eye. The results of characterization showed that the as-synthesized CdS photocatalyst has a high specific surface area and narrow band gap, which is favorable for light absorption and photocatalytic reaction. This work provides a new way to search for efficient visible-light catalysts and confirms the uniqueness of a biotemplated synthesis method in obtaining specially structured materials.

One-Pot Hydrothermal Synthesized Nitrogen and Sulfur Codoped Carbon Dots for Acid Corrosion Inhibition of Q235 Steel.

N and S codoped carbon dots having good water solubility have been successfully made by a novel hydrothermal method and characterized by FTIR, XPS, and TEM. The as-synthesized CDs were carbon particles rich in polar functional groups less than 10 nm in size. Electrochemical measurements, gravimetry, and surface analysis methods were utilized to examine the inhibition characteristics and adsorption mechanism of CDs on the carbon steel in acid pickling solutions. Electrochemical measurements verified that the CDs displayed adequate protection with high inhibition efficiency of 97.8%. The long-term weight-loss experiments up to 72 h further confirmed the excellent corrosion inhibition at room temperature and 313 K. The results presented are helpful for the formulation of more effective acid pickling corrosion inhibitors.

Dual Fluorometric Detection of Fe3+ and Hg2+ Ions in an Aqueous Medium Using Carbon Quantum Dots as a "Turn-off" Fluorescence Sensor.

The present study aimed to develop a carbon dots-based fluorescence (FL) sensor that can detect more than one pollutant simultaneously in the same aqueous solution. The carbon dots-based FL sensor has been prepared by employing a facile hydrothermal method using citric acid and ethylenediamine as precursors. The as-synthesized CDs displayed excellent hydrophilicity, good photostability and blue fluorescence under UV light. They have been used as an efficient "turn-off" FL sensor for dual sensing of Fe3+ and Hg2+ ions in an aqueous medium with high sensitivity and selectivity through a static quenching mechanism. The lowest limit of detection (LOD) for Fe3+ and Hg2+ ions was found to be 0.406µM and 0.934µM, respectively over the concentration range of 0-50µM. Therefore, the present work provides an effective strategy to monitor the concentration of Fe3+ and Hg2+ ions simultaneously in an aqueous medium using environment-friendly CDs.

A brief study on the Eriochrome Black T photodegradation kinetic by CdS/BiVO4 coupled catalyst

The coupled CdS/BiVO4 coupled catalyst was prepared via mechanical mixing of the as-synthesized CdS and BiVO4 NPs. Samples were investigated by scanning electron microscope (SEM), X-ray diffraction diffractometer (XRD), UV–Vis diffuse reflectance spectroscope (DRS), and Furrier transformation infrared spectrophotometer (FT-IR). The average crystallite sizes for CdS, BiVO4, and CdS/BiVO4 were obtained about 5.8, 34.9, and 37.3 nm By the Scherrer formula), and about 1.7, 23.1, and 12.5 nm (by the Williamson-Hall formula), respectively. The absorption edges of 622, 529, and 571 nm corresponding to bandgap energies of 1.99, 2.24, and 2.17 eV were respectively obtained for CdS, BiVO4, and CdS/BiVO4. A boosted photocatalytic activity of the coupled system was observed in the photodegradation of EBT (Eriochrome Black T). When moles of the BiVO4 component were 3–4 times greater than CdS, the highest activity was achieved. The rate constant of 0.032 min−1 and 0.007 min−1 were respectively obtained by the absorbencies recoded for the photodegraded EBT solutions and chemical oxygen demand (COD) data obtained in the photodegraded solutions. These values correspond to t1/2-values of 21.7 min and 99 min for the degradation and mineralization of EBT molecules during the photodegradation process. Here, a cheap and straightforward mechanical method was used to prepare the binary visible-light active CdS/BiVO4 photocatalyst with satisfying charge carriers’ transfer and good photocatalytic activity.

Green synthesis of a novel carbon dots from red Korean ginseng and its application for Fe2+ sensing and preparation of nanocatalyst

In the current study, we have synthesized a novel spherically shaped, water-soluble and green carbon dots (CDs, 2 nm) from a renewable source, aqueous root extract of red Korean ginseng (RKG) via highly efficient microwave irradiation method. The as-synthesized CDs showed excitation-dependent fluorescence emission behavior and therefore, applied for the selective detection of Fe2+ ions via fluorescent quenching method with the detection limit of 0.27 μM. We also investigated the effect of pH and high salt concentration on the fluorescent intensity of CDs. After that, silver nanoparticles (AgNPs, 15 nm) were synthesized using those CDs without adding additional reducing and stabilizing agents. The as-synthesized AgNPs showed high catalytic efficiency in reducing/degrading organic dyes, such as rhodamine B (RhB), methyl orange (MO) and congo red (CR) in presence of NaBH4. The pseudo first order rate constants for the reduction of RhB, MO and CR at room temperature were 0.27, 0.26 and 0.18 min−1 respectively. The synthesized AgNPs were also tested for the catalytic reduction of carcinogenic Cr (VI) to non-toxic Cr (III) in presence of formic acid, and ∼85% reduction was obtained within 15 min. All these results clearly demonstrated that the novel green CDs and the CD-derived AgNPs have multiple applications in the field of sensing and catalysis.

Synthesis of Group II-VI Semiconductor Nanocrystals via Phosphine Free Method and Their Application in Solution Processed Photovoltaic Devices.

Solution-processed CdTe semiconductor nanocrystals (NCs) have exhibited astonishing potential in fabricating low-cost, low materials consumption and highly efficient photovoltaic devices. However, most of the conventional CdTe NCs reported are synthesized through high temperature microemulsion method with high toxic trioctylphosphine tellurite (TOP-Te) or tributylphosphine tellurite (TBP-Te) as tellurium precursor. These hazardous substances used in the fabrication process of CdTe NCs are drawing them back from further application. Herein, we report a phosphine-free method for synthesizing group II-VI semiconductor NCs with alkyl amine and alkyl acid as ligands. Based on various characterizations like UV-vis absorption (UV), transmission electron microscope (TEM), and X-ray diffraction (XRD), among others, the properties of the as-synthesized CdS, CdSe, and CdTe NCs are determined. High-quality semiconductor NCs with easily controlled size and morphology could be fabricated through this phosphine-free method. To further investigate its potential to industrial application, NCs solar cells with device configuration of ITO/ZnO/CdSe/CdTe/Au and ITO/ZnO/CdS/CdTe/Au are fabricated based on NCs synthesized by this method. By optimizing the device fabrication conditions, the champion device exhibited power conversion efficiency (PCE) of 2.28%. This research paves the way for industrial production of low-cost and environmentally friendly NCs photovoltaic devices.

Lysosome-targeted carbon dots for colorimetric and fluorescent dual mode detection of iron ion, in vitro and in vivo imaging

In this work, a colorimetric and fluorescent dual mode sensor based on lysosome-targeted CDs has been desirably implemented to identify Fe3+ fluctuations in vitro and in vivo. By simple one-pot hydrothermal carbonization of dried field mint, yellow-fluorescent CDs were directly fabricated without the assistance of other reagents and hold exceptional stability, superior biocompatibility as well as ultra-low cytotoxicity. Results indicated that as-prepared CDs can provide a rapid, reliable, and highly selective recognition of Fe3+ with a linear range of 0 μM–400 μM and a detection limit of 0.037 μM. Impressively, it was found that as-developed CDs can successfully target lysosome with high colocalization coefficient (0.85) and responds to fluctuations of Fe3+ in living cells. Further, acquired CDs was ingeniously devoted to Escherichia coli imaging. Besides, obtained CDs was eventually utilized to track the variation of Fe3+ in vivo system. A preliminary research expresses that as-synthesized CDs can function as an effective tool to detect Fe3+ in vitro and in vivo and thus indicates the promising applicability for disease detection in physiology and pathology in the future.

In situ growth of 1D/2D CdS–Bi2MoO6 core shell heterostructures for synergistic enhancement of photocatalytic performance under visible light

Stability of the photocatalyst, maximum solar energy harvesting and effective photogenerated charge carrier separation are yet demanding key features of the photocatalysis for pollutant abetment and photo-electrochemical applications. Herein, we report the in situ solvothermal synthesis of CdS–Bi2MoO6 core-shell heterostructures (CdS–Bi2MoO6 CSHs) for the photocatalytic elimination of methyl orange (MO) under visible light. The as-synthesized CdS–Bi2MoO6 CSHs exhibited highest photocatalytic performance of 98.5%, which is approximately 10 and 4 folds higher than pristine Bi2MoO6 nanosheets (NSs) and CdS nanorods (NRs), respectively. This significantly enhanced photocatalytic performance is attributed to the core-shell heterostructure that improves the visible-light harvesting ability, facilitates efficient separation and transfer of the photogenerated charge carriers, as well as synergistic band alignment of both CdS NRs and Bi2MoO6 NSs. The CdS–Bi2MoO6 CSHs also showed efficient photocatalytic performance toward methylene blue (MB) as colored dye and tetracycline hydrochloride (TCH) as a colorless emerging contaminant. Additionally, the outcomes of transient photocurrent, electrochemical impedance, and photoluminescence study further corroborate that the construction of core-shell heterostructures with tight contact, leading to effective charge carrier separation. The hole (h+) and superoxide radical anion (•O2−) were determined to be the predominant active species accountable for the MO dye degradation. Furthermore, the CdS–Bi2MoO6 CSHs exhibited a satisfactory recycling efficiency over five cycles (reduced by approximately 6%), owing to the protective Bi2MoO6 NSs shell over the CdS NRs core, demonstrating their applicability in wastewater purification and photo-electrochemical applications.

Visible Light-Driven Photocatalytic Rhodamine B Degradation Using CdS Nanorods

In this work, highly crystalline CdS nanorods (NRs) were successfully synthesized by a facile, one-step solvothermal method. The as-prepared CdS NRs powder was characterized by XRD, FESEM, Raman, PL, XPS, BET, and UV-visible techniques to evaluate the structural, morphological, and optical properties. The photocatalytic performance of the as-synthesized CdS NRs was investigated for the photodegradation of RhB dye under visible light irradiations. It has been found that CdS NRs show maximum RhB degradation efficiency of 88.4% in 120 min. The excellent photodegradation ability of the CdS NRs can be attributed to their rod-like structure together with their large surface area and surface state. The kinetic study indicated that the photodegradation process was best described by the pseudo-first-order kinetic model. The possible mechanism for the photodegradation of RhB dye over CdS NRs was proposed in this paper.

CdS–Ag3PO4 nano-catalyst: A brief characterization and kinetic study towards methylene blue photodegradation

CdS and Ag3PO4 NPs were synthesized by the sol-gel method and coupled mechanically. The XRD analysis showed the hexagonal (wurtzite) CdS and the body-centered cubic of Ag3PO4 crystallite phases in the resulted nano-catalyst (NC). The average crystallite sizes of 2.07, 25.36, and 20.83 nm were respectively obtained for the as-synthesized CdS, Ag3PO4, and CdS–Ag3PO4 samples by the Scherrer equation which varied to 1.25, 49.52 and 55.46 nm based on the Williamson-Hall equation. The samples were also characterized by scanning electron microscope (SEM), UV–Vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) techniques. A boosted photocatalytic activity for the coupled system was observed due to the better charge carrier's separation that occurred in this system. The lowest PL intensity and the highest photodegradation activity were obtained for the NC with a CdS:Ag3PO4 mole ratio of 2. The mineralization extent of the MB photodegraded solutions was studied by the COD method. The rate constants of 0.0108 and 0.0132 min−1 were obtained for the MB-photodegradation and mineralization processes by applying the results in the Hinshelwood apparent first-order kinetic model, respectively. These values correspond to t1/2 values of 64.2 min and 22.2 min, respectively. The k-values of 0.0095, 0.0086, 0.0075 and 0.0075 min−1 (average: 0.0083 ± 0.0009 min−1) with a RSD of 12% were obtained for 4 successive reusing runs for the NC.

Cadmium sulfide nanoparticles: Synthesis, brief characterization and experimental design by response surface methodology (RSM) in the photodegradation of ranitidine hydrochloride

CdS nanoparticles (NPs) were synthesized and briefly characterized by XRD, FTIR, BET, DRS, and SEM-EDX techniques. A cubic-zinc blende structure for CdS NPs was identified by XRD pattern. The EDX results confirmed an atomic percentage Cd: S ratio of 49:51 for the sample. The BET surface area, total pore volume, and the mean pore diameter of 120 m2/g, 0.1395 cm3/g, and 4.5 nm were also obtained, respectively. The absorption edge wavelength of 610 nm showed the bandgap energy (Eg) of 2.03 eV. The as-synthesized CdS NPs were then used in the photodegradation of ranitidine (RD). The simultaneous effects of the influencing variables were evaluated by designing the experiments by using a central composite design with response surface methodology (RSM) approach. The best RD degradation extent was obtained at a run including pH 6.2, catalyst dose of 0.6 g/L, 3.4 mg/L of ranitidine at irradiation time of 97.5 min. The high correlation coefficient (R2 = 0.9739) for the quadratic polynomial model, showed that the data predicted by RSM were in good agreement with those obtained in experimental runs. Finally, the COD and HPLC analysis of the photodegraded RD solutions confirmed the degradation of RD molecules. A rate constant value of 0.014 min−1 correspond to t1/2 value of 49.5 min was obtained by COD results for the mineralization of RD or its degradation intermediates.

Synthesis of Ni-silicate superficially modified CdS and its highly improved photocatalytic hydrogen production

Development of photocatalytic hydrogen production through water splitting is promising due to its practical application in converting solar energy into chemical energy. Herein, we report a facile surface decoration of Ni-silicate nanosheet onto CdS nanorods (denote as CdS NRS) to establish an excellent visible-light-driven photocatalyst for hydrogen evolution. The as-synthesized CdS NRS@Ni-silicate exhibits an impressively ameliorated performance in the subsequent photocatalysis, engendering 401.7 µmol·h−1 hydrogen, which is 8.9 times higher than that conducted by pure CdS. The improvement in catalytic activity primarily owes much to two contributors: The embedded Ni2+ act as cocatalyst in silicate that enhance the separation efficiency of photo-induced carriers; the silicate layer greatly scatters the Ni2+ ion and consequently keeps it from aggregation on the CdS surface.

Umbrella-like CdS single crystal: exposed (002) facets and enhanced photocatalytic properties

We, herein, report the synthesis of umbrella-like CdS single crystal with exposed high-activity (002) facets first time by using a one-step hydrothermal method with cadmium acetate dihydrate (Cd(CH3COO)2·2H2O) and ammonium thiocyanate (NH4SCN), and its possible growth mechanism was discussed. As a contrast, CdS nanoparticles with different morphologies were also synthesized. The morphology, composition and photocatalytic property of as-synthesized samples were determined by XRD, SEM, TEM, UV–Vis DRS, PL and photocurrent tests, respectively. The results show that umbrella-like CdS under UV (20 min) and visible light (80 min) irradiation, the removal rate of rhodamine B was as high as 99.1% and 99.3%, respectively. Moreover, even though the particle size of umbrella-like CdS particle is larger than as-synthesized CdS nanospheres, it still shows excellent photocatalytic degradation activity due to its exposed high-energy (002) facets. And its excellent application prospects are conceivable. The current work provides a new paradigm in material morphology design, especially in the construction of highly active surfaces for photocatalysis and photoelectric conversion.

Mid-infrared photoconductivity of polypyrrole doped with cadmium sulfide quantum dots

We report the facile (one-step) in situ doping of soluble conducting polypyrrole (PPy) with cadmium sulfide quantum dots (CdS QDs) aimed at tuning the mid-infrared (MIR) (2.5–25 μm) photoconductivity of PPy films with a planer structure. The doping was done during chemical polymerization of PPy with different mass ratios (0–1800 ppm) of the as-synthesized CdS QDs. The PPy/CdS QDs films were fabricated by electrospray coating between gold interdigitated electrodes. The incident light in the MIR region (7.62 mW/cm2) was chopped, the prepared film was illuminated with it, and the photocurrent generated was recorded. Doping with CdS QDs at 2–15 ppm increased the photoconductivity of PPy as they generated greater photocurrent than the undoped PPy, which is attributed to the conductivity enhancement in the doped polymers. More addition of CdS QDs (>15 ppm) decreased the photoconductivity of PPy. So, the best doping concentration was found to be 15 ppm, which produced an average photocurrent of 177.3 μA, which exhibited a large photosensitivity of 1772 and photoresponsivity of 23.25 mA/W. We showed that the in situ doping not only increases the mobility of generated charge carriers in the polymer but also narrows the optical band gap of PPy by about 0.13 eV, enabling more absorption in the MIR region. Essential to this success was the UV–visible characterization of PPy doped with CdS QDs followed by Tauc calculations, which verified the narrowing of the band gap. The high-performance photoconductivity of PPy/CdS QDs films in the MIR region suggested their potential applicability in organic electronic devices.