Silver-Based Metal Sulfide Heterostructures: Synthetic Approaches, Characterization, and Application Prospects

Guria A.K., Sarkar S., Patra B.K., Pradhan N.

How efficient could a superionic conductor catalyst be? Beyond the traditionally used molecular precursors when the solution dispersed solid nanomaterials of variable size, shape and phase are introduced under certain reaction condition; the catalyst is found to digest all these structures in minutes irrespective of their phase and morphology, resulting unique heteronanowires. This has been inspected here by employing different ZnSe nanostructures as precursor for Ag2Se nanocrystal catalyst in its superionic conductor phase to obtain the Ag2Se-ZnSe heteronanowires. This dissolution and formation process of these nanostructures is correlated with the change in the reaction temperature profile, the phase of the catalyst, the shape/phase and surface ligands of the source nanostructures, and the possible mechanism of the unique heteronanowires growth has been investigated.

Huang Z., Li M., Jia D., Zhong P., Tian F., Chen Z., Humphrey M.G., Zhang C.

Semiconductor–semiconductor hetero-nanorods (Ag2Se–CdSe and Ag2Se–ZnSe) with high crystallinity have been synthesized by a facile and low-cost method. High resolution transmission electron microscopy investigations reveal that the growth follows a catalyst-assisted mechanism. A preliminary investigation of nonlinear optical properties shows that the hetero-nanorods exhibit significantly enhanced third-order nonlinear optical properties. The free carrier absorption cross-section of Ag2Se–CdSe hetero-nanorods is one order of magnitude higher than that of the corresponding single component CdSe nanocrystals. The results obtained in this study represent a new approach to the design and construction of metal selenide hetero-nanorods with high crystallinity and enhanced nonlinear optical capabilities.

Bose R., Manna G., Jana S., Pradhan N.

A single nanostructure p–n junction diode has been fabricated colloidally by synthesizing a heterostructure comprising of p-type Ag2S and n-type AgInS2, where the quasi type-II band alignment of the constituents further improve charge separation.

Wang J., Feng H., Chen K., Fan W., Yang Q.

Ag2S nanocrystals are catalytically active in the growth of CdS nanorods in oleylamine, and the reaction yields Ag2S–CdS matchstick-like heteronanostructures.

Mahadevu R., Yelameli A.R., Panigrahy B., Pandey A.

Semiconductor nanocrystals of different formulations have been extensively studied for use in thin-film photovoltaics. Materials used in such devices need to satisfy the stringent requirement of having large absorption cross sections. Hence, type-II semiconductor nanocrystals that are generally considered to be poor light absorbers have largely been ignored. In this article, we show that type-II semiconductor nanocrystals can be tailored to match the light-absorption abilities of other types of nanostructures as well as bulk semiconductors. We synthesize type-II ZnTe/CdS core/shell nanocrystals. This material is found to exhibit a tunable band gap as well as absorption cross sections that are comparable to CdTe. This result has significant implications for thin-film photovoltaics, where the use of type-II nanocrystals instead of pure semiconductors can improve charge separation while also providing a much needed handle to regulate device composition.

Chang C., Chen J., Chen C., Yang C., Chang J.

A cadmium-free CuInS2 quantum dot (QD)-sensitized solar cell (QDSC) has been fabricated by taking advantage of the ex situ synthesis approach for fabricating highly crystalline QDs and the in situ successive ionic-layer adsorption and reaction (SILAR) approach for achieving high surface coverage of QDs. The ex situ synthesized CuInS2 QDs can be rendered water soluble through a simple and rapid two-step method under the assistance of ultrasonication. This approach allows a stepwise ligand change from the insertion of a foreign ligand to ligand replacement, which preserves the long-term stability of colloidal solutions for more than 1 month. Furthermore, the resulting QDs can be utilized as sensitizers in QDSCs, and such a QDSC can deliver a power conversion efficiency (PCE) of 0.64%. Using the SILAR process, in situ CuInS2 QDs could be preferentially grown epitaxially on the pre-existing seeds of ex situ synthesized CuInS2 QDs. The results indicated that the CuInS2 QDSC fabricated by the combined ex situ/in situ growth process exhibited a PCE of 1.84% (short-circuit current density = 7.72 mA cm–2, open-circuit voltage = 570 mV, and fill factor = 41.8%), which is higher than the PCEs of CuInS2 QDSCs fabricated by ex situ and in situ growth processes, respectively. The relative efficiencies of electrons injected by the combined ex situ/in situ growth approach were higher than those of ex situ synthesized CuInS2 QDs deposited on TiO2 films, as determined by emission-decay kinetic measurements. The incident photon-to-current conversion efficiency has been determined, and electrochemical impedance spectroscopy has been carried out to investigate the photovoltaic behavior and charge-transfer resistance of the QDSCs. The results suggest that the combined synergetic effects of in situ and ex situ CuInS2 QD growth facilitate more electron injection from the QD sensitizers into TiO2.

Wang J., Chen K., Gong M., Xu B., Yang Q.

The catalytic mechanism offers an efficient tool to produce crystalline semiconductor nanowires, in which the choice, state, and structure of catalysts are active research issues of much interest. Here we report a novel solution-solid-solid (SSS) mechanism for nanowire growth catalyzed by solid-phase superionic conductor nanocrystals in low-temperature solution. The preparation of Ag2Se-catalyzed ZnSe nanowires at 100-210 °C is exampled to elucidate the SSS model, which can be extendable to grow other II-VI semiconductor (e.g., CdSe, ZnS, and CdS) nanowires by the catalysis of nanoscale superionic-phase silver or copper(I) chalcogenides (Ag2Se, Ag2S, and Cu2S). The exceptional catalytic ability of these superionic conductors originates from their structure characteristics, known for high-density vacancies and fast mobility of silver or copper(I) cations in the rigid sublattice of Se(2-) or S(2-) ions. Insights into the SSS mechanism are provided based on the formation of solid solution and the solid-state ion diffusion/transport at solid-solid interface between catalyst and nanowire.

Yang X., Tang Y., Tan S.T., Bosman M., Dong Z., Leck K.S., Ji Y., Demir H.V., Sun X.W.

Highly luminescent semiconducting AgInS2–ZnS solid solution nanorods are successfully prepared by a facile one-pot solvothermal method. The resulting solid solution nanorods with length of 32 ± 5 nm are formed by fast growth of the AgInS2-rich solid solution head, followed by slow growth of the ZnS-rich solid solution tail. Photoluminescence studies on the solid solution nanorods reveal strong photoluminescence with peak emission wavelengths tunable from 650 to 700 nm.

Huang Z., Pan L., Zhong P., Li M., Tian F., Zhang C.

A facile method for the low-cost and large-scale production of ultralong Ag(2)S (or Ag(2)Se)-ZnSe quantum wires has been developed. ZnSe quantum wires (diameter≈4 nm) with high uniformity in their crystal structure and diameter can be synthesized by using a catalyst-assisted growth approach with Ag(2)S nanoparticles as a catalyst. The influence of the growth temperature, time, and type of catalytic particle on the morphology of the ZnSe quantum wires was systematically explored. Besides Ag(2)S, Ag(2)Se nanoparticles can also be adopted as the catalyst for the growth of ZnSe wires. This method can also be applied to the fabrication of uniform CdSe nanorods. This method is convenient for the controllable fabrication of metal selenides and is of importance for exploring fundamental nanoscale semiconductor physics, as well as for affording technological devices with optimized characteristics.

Ojea-Jiménez I., García-Fernández L., Lorenzo J., Puntes V.F.

The present work faces the rising demand of cationic particles of different sizes for biological applications, especially in gene therapies and nanotoxicology studies. A simple phase-transfer methodology has been developed for the functionalization of gold nanoparticles (Au NPs) with a variety of ligands, both cationic and anionic in aqueous solution, employing different nanocrystal sizes with narrow size distributions. Successful functionalization has been demonstrated by UV–vis spectroscopy, DLS, ζ-potential, and FTIR spectroscopy characterization of the particles before and after the phase transfer. The intracellular uptake of the differently charged Au NPs functionalized with peptidic biomolecules was investigated with human fibroblasts (1BR3G) by ICP-MS analysis of the digested cells and confocal fluorescence microscopy, which showed increased internalization of the cationic bioconjugates. Nuclear targeting could be observed by TEM, suggesting that the cationic peptidic biomolecule is acting as a nuclear localization signal.

Zhuang T., Fan F., Gong M., Yu S.

Unique Cu(2)S-PbS heteronanostructures with good photothermal conversion effect have been synthesized for the first time by a Cu(1.94)S nanocrystal seed mediated colloidal solution-phase growth method. The present nanocrystal seed mediated growth method may be extended for the growth of other unique semiconductor heteronanostructures.

Huang Z., Zhong P., Li M., Tian F., Zhang C.

A simple and facile method for synthesizing Ag(2)S-CdS nanoheterostructures has been introduced. With a one-step hydrothermal reaction, Ag(2)S-CdS nanoheterostructures with high uniformity in morphology and structure can be obtained. The Ag(2)S-CdS nanoheterostructures exhibit matchstick-like morphology, composed of spherical Ag(2)S heads and CdS rods. The influences of the reaction temperature, reaction time and molar ratio between Ag and Cd sources were explored, the results suggesting that the growth can be ascribed to the in situ phase transfer of Ag and Cd sources from the aqueous phase to the organic phase and the subsequent catalyst-assisted growth.

Jiang P., Zhu C., Zhang Z., Tian Z., Pang D.

A one-step method for synthesizing water-soluble Ag(2)S quantum dots terminated with carboxylic acid group has been reported. The crystal structure and surface of the prepared Ag(2)S quantum dots were characterized. The prepared Ag(2)S quantum dots exhibited bright photoluminescence and excellent photostabilities. The photoluminescence emissions could be tuned from visible region to near-infrared (NIR) region (from 510 nm to 1221 nm). Ultra-small sized Ag(2)S nanoclusters were synthesized with high initial monomer concentration in the current system. The in vivo imaging experiments of nude mice showed that the NIR photoluminescence of the prepared Ag(2)S quantum dots could penetrate the body of mice. Compared to the conventional NIR quantum dots, the Ag(2)S quantum dots don't contain toxic elements to body (such as Cd and Pb), thus, the prepared Ag(2)S quantum dots could serve as excellent NIR optical imaging probes and would open the opportunity to study nanodiagnostics and imaging in vivo.

Meng Z., Ghosh T., Zhu L., Choi J., Park C., Oh W.

We improve the photocatalytic effect of Ag2S under visible light by using fullerene modified with Ag2S nanoparticles. Surface areas and pore volumes of the Ag2S–fullerene samples showed catastrophic decreases due to the deposition of Ag2S. The generation of reactive oxygen species was detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). It is found that the photocurrent density and the photocatalytic effect increase in the case with the modified fullerene. In comparison with the separate effects of Ag2S and fullerene nanoparticles, the photocatalytic effect of the fullerene modified with Ag2S composites is increased significantly due to the synergetic effect between the fullerene and the Ag2S nanoparticles.

Shen S., Zhang Y., Liu Y., Peng L., Chen X., Wang Q.

Doping semiconductor nanocrystals and integrating disparate components together are two effective ways for modulating the optical properties of semiconductor nanocrystals. For the first time, we successfully synthesized Mn-doped Ag2S-ZnS heteronanostructures (HNSs) by combining these two strategies together. The obtained Mn-doped Ag2S-ZnS HNSs exhibit multicolor emissions of blue, orange, and near-infrared (NIR), in which the blue emission originates from ZnS trap state, the orange emission is induced by the 4T1–6A1 transition in Mn2+ dopant, and the NIR emission is attributed to the band gap emission of Ag2S. Reaction temperature-dependent and Mn2+ dopant concentration-dependent optical properties, as well as the growth kinetics of Ag2S-ZnS HNSs during doping process, were systemically studied to achieve the desirable optical properties and preserve well-defined HNSs simultaneously. We expect that the prepared Mn-doped Ag2S-ZnS HNSs with tunable multicolor emissions will create numerous opportunities for...

Tan K., Yang Z., Zhu Y., Liu B., Zhao L., Song L., Yu S.

Shao R., Wang M., Xue Y., Zhang N., Wang A., Song P., Mei L., Feng J.

Myoglobin (Mb), an important cardiac marker, plays a crucial role in diagnosing, monitoring, and evaluating the condition of patients with cardiovascular diseases. Here, we propose a label-free photoelectrochemical (PEC) sensor for the detection of Mb through target regulated the photoactivity of Ag2S/FeOOH heterojunction. The Ag2S/FeOOH nanospindles were synthesized and served as a sensing platform for the fabrication of bio-recognized process for Mb. Mb-aptamer was used as the responsive group to grasp the target Mb in a real sample due to its advantages of strong affinity, high stability, and ease of preparation. Mb-aptamer immunocomplex is formed in the presence of Mb, which hinders the interfacial electron transfer and then reduce the photocurrent. The proposed PEC aptasensor exhibited excellent analytical performance including wide linear range (1.0 pg mL−1 ~ 50 ng mL−1), low limit of detection (0.28 pg mL−1), and good selectivity and stability. This work introduces an innovative approach to PEC aptasensor, offering a promising method for precise determination of human biomarkers.

Rempel Andrey A., Ovchinnikov Oleg V., Weinstein Ilya A., Rempel Svetlana V., Kuznetsova Yulia V., Naumov Andrei V., Smirnov Mikhail S., Eremchev Ivan Yu., Vokhmintsev Alexander S., Savchenko Sergey S.

Quantum dots are the most exciting representatives of nanomaterials. They are synthesized using advanced methods of nanotechnology pertaining to both inorganic and organic chemistry. Quantum dots possess unique physical and chemical properties; therefore, they are used in very different fields of physics, chemistry, biology, engineering and medicine. It is not surprising that the Nobel Prize in chemistry in 2023 was given for discovery and synthesis of quantum dots. This review addresses modern methods for the synthesis of quantum dots and their optical properties and practical applications. In the beginning, a short insight into the history of quantum dots is given. Many gifted scientists, including chemists and physicists, were engaged in these studies. The synthesis of quantum dots in solid and liquid matrices is described in detail. Quantum dots are well-known owing to their unique optical properties; that is why the attention in the review is focused on the quantum-size effect. The causes for fascinating blinking of quantum dots and techniques for observation of a single quantum dot are considered. The last part of the review describes mportant applications of quantum dots in biology, medicine and quantum technologies.The bibliography includes 772 references.

Karkhaneh A., Marandi M.

Mehra S., Singh K., Kumar A.

Wang L., Cao X., Liu Z., Wang Y., Xiong P., Gao W., Tang B.

Exploring excellent NIR-II emitting materials is desirable for the advancement of high quality bioimaging, in virtue of the lower scattering, deep penetration and high sensitive of biological components in the second optical transmission window. Colloidal Ag 2 X (X = S, Se) nanocrystals exhibit tunable NIR photoluminescence in the second NIR region. However, the lack of highly efficient broadband NIR emitting Ag 2 X (X = S, Se) nanocrystals limits their spectroscopy applications. Herein, cadmium (Cd) doped Ag 2 X (X = S, Se) nanocrystals were prepared through a facile hydrothermal method at room temperature. The NIR luminescence was efficiently enhanced through controllable doping a little amount of Cd ions into the Ag 2 X (X = S, Se) quantum dots (QDs). Simultaneously, the great broadening of NIR emission was achieved in the Cd doped Ag 2 Se QDs, and the maximum full width at half maximum could reach up to 530 nm. Following the general principles of PL LED devices, the fabricated NIR mini light-emitting diodes (LEDs) light sources based on Cd doped Ag 2 Se QDs exhibited broadband NIR electroluminescence and superior optoelectronic stability, and were successfully employed for clear vessel imaging. The works proves the feasibility of NIR mini LEDs in non-invasive bioimaging, and paves way for the miniaturized broadband NIR light sources. • NIR emission of Ag 2 X (X = S, Se) QDs are enhanced more than 3 times via Cd doping. • Broadband Dual NIR emission of Cd doped Ag 2 Se QDs covers the entire NIR-II region. • The addition of Cd ions induces the variation of bandgap energy of Ag 2 Se QDs. • Micron-scale non-invasive vessel imaging is achieved by doped QDs converted NIR LED.

Sen S., Bera S., Pradhan N.

Bashir M., Aman S., Awan A., Nazar M.F., Zubair M., Nadeem R., Zafar M.N.

The global challenges relating to energy harvesting could be solved using nanotechnology, which provides progressively elaborated and ingenious geometric structures, which can incorporate an accrescent material surface. For this purpose of energy harvesting, metal sulfides are serving as an emerging generation. For the conversion of electrochemical energy, metal sulfides have gained considerable attention as favorable electrode material due to their remarkable electrochemical performance including broad potential windows and elevated theoretical capacities. The production of electricity from the waste heat by thermoelectric material is of great interest because of its reliability and simplicity, which enhances energy efficiency. There are some scientific and civil problems regarding the achievement of power densities and high energy for electrochemical conversion. The possible solution to increasing energy demand around the world, for today and to the next generation, is the production of electrical energy directly from light. In this chapter, we have discussed the process by which metal sulfide nanocomposites can be used for energy harvesting, their utilization for eco-friendly and renewable energy demands, and its efficient storage from alternate sources. This chapter also includes different types of nanocomposites of metal sulfides, their synthetic route including one-step electrode coating method, atomic layer deposition method, one-step high-temperature solvothermal synthesis, hydrothermal method, metal sulfide deposition method, wet chemical method, low-temperature water bath technique and modified hummers method followed by hydrothermal method, hard templating method, soft templating method, and sacrificial templating method, and one step hydrothermal and sol-gel synthesis method. For the elucidation of their structural and morphological characteristics and functional properties, different techniques including SEM, TEM, X-ray photoelectron spectroscopy (XPS), UV/Vis absorption spectroscopy, XRD, cyclic voltammetry (CV), FTIR, BET (surface and pore size studies) and TGA have been discussed. Analysis for application potential of metal sulfides is elaborated based on several modes of their applications including photo/electrochemical energy storage and conversion, semiconductor solar cells, photocatalytic hydrogen production, electrochemical capacitors, hybrid solar cells with enhanced photocurrent, and solar energy harvesting. Some of the future concerns are also discussed related to their feasibility, production of composites containing multifunctional hybrids, stability and life span of composite, solution or medium for their regeneration, and their safe dumping.

Li Y., Liu Y., Gao G., Zhu Y., Wang D., Ding M., Yao T., Liu M., You W.

A novel core-shell heterojunction of p-Ag 2 S/n-AgInS 2 nanoflowers built by interlaced and slightly-curved nanosheets is fabricated for the first time by a facile one-pot one-step L-cysteine and urea synergistically-mediated hydrothermal method and demonstrates 36- and 3.4-fold enhancement for MO degradation under visible light as compared to neat Ag 2 S and AgInS 2 , respectively. • p-Ag 2 S/n-AgInS 2 core-shell heteronanoflowers fabricated by a facile one-pot hydrothermal route. • A sacrificial in-situ self-transformation mechanism was proposed. • Better photocatalytic performance for MO degradation than neat Ag 2 S and AgInS 2 . Delicate design and construction of Ag 2 S-based heterostructures with favorable interface for prominent charge separation is a grand challenge in photocatalysis. In this work, the large-scale fabrication of core-shell p-Ag 2 S/n-AgInS 2 hetero-nanoflowers with interlaced nanosheets is demonstrated firstly by a facile one-pot one-step L-cysteine and urea co-mediated hydrothermal method. Here in-situ partial self-transformation of initially-generated monoclinic Ag 2 S nuclei (core) to orthorhombic AgInS 2 (shell) plays a critical role in creating an atomic-level p-n nanojunction between p-Ag 2 S and n-AgInS 2, which is validated by various techniques including XRD, SEM, HR(TEM), EDS, XPS, N 2 adsorption/desorption and UV–vis DRS spectra. Benefiting from the enhanced light-response and charge-separation due to the establishment of p-n heterojunction, the photocatalytic activity of Ag 2 S/AgInS 2 heteronanoflowers (In/Ag = 1.0, molar ratio) for MO degradation under visible light is nearly 36 and 3.4 times higher than that of pristine Ag 2 S and AgInS 2 , respectively. More Intriguingly, Ag 2 S/AgInS 2 hetero-nanoflowers manifest exceptionally preferable photo- and chemical-stability as well as anti-photocorrosion capability, a formidable challenge encountered in many chalcogenides. This work not only highlights the great potential of Ag 2 S/AgInS 2 hetero-nanoflowers as a less-toxic visible-light active photocatalyst, but also affords a cost-competitive and eco-friendly one-pot strategy towards in-situ fabrication of sulfide-based heterostructures with favorable interface for good performance in solar energy-related applications.

Soto Morillo E., Mota Toledo N., García Fierro J.L., Navarro Yerga R.M.

The aim of this work is to study the influence of the sulphur source (elemental sulphur, thiourea and L-cysteine) in the solvothermal synthesis of Ag-CdS over its growth, structuration and state of Ag and how these changes influence on its photoactivity. The differences in the generation rate of the S2− from the sulphur sources during the solvothermal synthesis determine the nucleation and growth pathways of CdS affecting to the silver state and its incorporation into the CdS lattice. The hydrogen production on Ag-CdS photocatalysts decreases according the sequence: thiourea > elemental sulphur >> L-cysteine. The changes in the photoactivity of Ag-CdS samples are analysed in terms of the differences in the insertion of Ag+ into the CdS lattice, the formation of composites between CdS and Ag2S and the formation of CdS crystalline domains with strong confinement effect derived from the different sulphur source used in the solvothermal synthesis.

Reznik I.A., Kurshanov D.A., Dubovik A.Y., Baranov M.A., Moshkalev S.A., Orlova A.O., Baranov A.V.

The photostability of the luminescent properties of CuInS2/ZnS quantum dots (CIS/ZnS QDs) as a monolayer on a dielectric substrate and as part of a hybrid structure with multilayer graphene nanoribbons (ML GNRs) has been studied. Analysis of the luminescence kinetics of quantum dots has revealed the presence of three main components of luminescence attenuation, characterized by times of the order of 20, 100, and 300 ns. It has been shown that the efficiency of the interaction between CIS/ZnS quantum dots and multilayer graphene nanoribbons has a dependence on the number of graphene monolayers similar to that of CdSe quantum dots. The photostability of CIS/ZnS QDs on a dielectric substrate and in structures with multilayer graphene nanoribbons has been estimated, which allowed us to estimate the energy/charge transfer rates from QDs to multilayer graphene nanoribbons as 106–107 s–1.

Liu Y., Chen H., Fan H., Chen Y., Wang F.

Solution-solid-solid (SSS) nanowires can be catalyzed by superionic Ag2S via ion diffusion. Here, we synthesize ZnS nanowires of the wurtzite crystal structure and heterostructures via a low-temperature growth pathway. Single-crystalline ZnS nanowires were produced by varying reaction time and temperature (120-200 °C) via thermal decomposition of a single-source precursor, Zn(DDTC)2. A phase transformation (zinc blende → wurtzite) was observed during the synthesis with a three-step growth pathway proposed. Temperature-controlled phase transformation facilitates oriented attachment into a 1D nanowire, followed by helical epitaxial and lateral growths during ripening. Additionally, the CdS-ZnS heterostructured nanowires can be obtained after introducing the Cd(DDTC)2 precursor. ZnS nanowires of defined diameters (5-10 nm) are served as backbones to grow heterostructures of ternary semiconductors with multicolor photoluminescence (450-800 nm). Structural and optical characterizations (PL, 2D PLE, and TCSPC) are investigated to confirm origins of broadband emission from multiple lifetimes (0.5-12 ns) for exciton recombination in heterostructures. Our study demonstrates this unique growth pathway for SSS nanowire synthesis under mild, facile, and atmospheric conditions.

Shen Y., Lifante J., Ximendes E., Santos H.D., Ruiz D., Juárez B.H., Zabala Gutiérrez I., Torres Vera V., Rubio Retama J., Martín Rodríguez E., Ortgies D.H., Jaque D., Benayas A., del Rosal B.

A critical analysis of the synthesis routes, properties and optical features of Ag2S nanoparticles is presented. The future perspectives of this material for advanced bioimaging are discussed.

Kumar T.K., Kumar S.K.

In the present work, new visible-light-active nanosized Ag2S-ZnS loaded on cellulose (AZCE) was synthesized by a precipitation method. The AZCE composite was systematically characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area, and UV-visible diffuse reflectance spectroscopy (UV-DRS). The activities of the photocatalysts were evaluated for rhodamine B dye (RhB) degradation under simulated sunlight and the amounts of the dye samples were analysed using a UV-vis spectrophotometer at λmax 554 nm. The effects of the reaction conditions such as pH, catalyst, hydrogen peroxide and dye concentration on the photodegradation rate have been investigated. The degradation profile reveals that 30 ppm of the dye could be effectively oxidized using 30 mg of the AZCE dose in the pH range 4-12 within 90 min. The oxidation of the RhB dye follows first-order kinetics and the rate constant was calculated to be 6.4 X 10−3 min−1. Various organic intermediates were identified during degradation using high performance liquid chromatography (HPLC), total organic content (TOC) and electron-spray ionizationmass spectrometry (ESI-MS). In order to determine the effectiveness of AZCE photocatalytic activity, other catalysts such as Ag2S loaded on cellulose (AZE) and ZnS loaded on cellulose (ZCE) were used as photocatalysts. The results show that photocatalytic activity follows the order AZCE > ACE > ZCE and this is due to the fact that a cellulose network is used as a catalyst carrier. The alkali pre-treated cellulose provides an activated surface hydroxyl groups to enhance the deposition efficiencies of Ag2S and ZnS and thereby a large amount of visible light can be absorbed and the photocatalytic activity is increased.

Halder G., Ghosh A., Parvin S., Bhattacharyya S.

Quantum dot-sensitized solar cells (QDSSCs), especially those based on ternary AgInX2 (X = S, Se) QDs, suffer from very low power conversion efficiencies (PCEs) owing to presence of high density of trap states and imperfect surface coverage by surfactants. This has a similar adverse effect on water photolysis when the solar cells are integrated with the electrolyzer. Passivation of the QD surface with an inorganic shell is vital and temporally regulated cation exchange can come to the rescue, whereby an alloyed shell can minimize the interfacial trap states which are mostly abundant in core/shell QDs with sharp interfaces. Herein, Zn–Ag–In–Se (ZAISE) core QDs were cation-exchanged with Cd2+ ions to create an alloyed shell of Ag–In–Zn–Cd–Se. When the QDs were used as absorbers, the PCE was enhanced from 3.01% for core ZAISE QDs to 4.71% for core/alloyed shell QDs by optimizing the shell thickness; 4.71% is also one of the superior PCEs in AgIn(S/Se)2-based photovoltaic systems. The density of states invest...