Pressure-induced bandgap engineering and photoresponse enhancement of wurtzite CuInS2 nanocrystals

Wurtzite CuInS₂ exhibits great potential for optoelectronic applications because of its excellent optical properties and good stability. However, exploring effective strategies to simultaneously optimize its optical and photoelectrical properties remains a challenge. In this study, the bandgap of wurtzite CuInS₂ nanocrystals is successfully extended and the photocurrent is enhanced synchronously using external pressure. The bandgap of wurtzite CuInS₂ increases with pressure and reaches an optimal value (1.5 eV) for photovoltaic solar energy conversion at about 5.9 GPa. Surprisingly, the photocurrent simultaneously increases nearly 3-fold and reaches the maximum value at this critical pressure. Theoretical calculation indicates that the pressure-induced bandgap extention in wurtzite CuInS₂ may be attributed to an increased charge density and ionic polarization between the In-S atoms. The photocurrent preserves a relatively high photoresponse even at 8.8 GPa, but almost disappears above 10.3 GPa. The structural evolution demonstrates that CuInS₂ undergoes a phase transformation from the wurtzite phase (P6₃mc) to the rock salt phase (Fm3̄m) at about 10.3 GPa, which resulted in a direct to indirect bandgap transition and fianlly caused a dramatic reduction in photocurrent. These results not only map a new route toward further increase in the photoelectrical performance of wurtzite CuInS₂, but also advance the current research of A^I-B^III-CVI2 materials.

In situ phase transformation of polytypic zinc-blende/wurtzite copper indium sulfide via a facile polyol method to boost visible-light photocatalytic performance

A zinc-blende/wurtzite (ZB/WZ) copper indium sulfide (CuInS₂/CIS) polymorph with high visible-light absorption ability and high charge separation rate was developed by using a facile polyol method. Results showed that when thioacetamide served as a sulfur precursor, the crystalline phase of CIS was zinc-blende. Meanwhile, when thiourea served as a sulfur precursor, the crystalline phase of CIS was wurtzite, which exhibited good photocatalytic acid red 1 (AR1) dye decolorization efficiency. When the precursor/ethylene glycol ratio was 1/50-7/50, the AR1 decolorization efficiency followed the order: T-5-CIS > T-7-CIS > T-3-CIS > T-1-CIS, and the TOC removal efficiency of T-5-CIS was 45.7%. The PL and EIS analyses indicated that T-5-CIS showed the highest charge separation rate. Mott-Schottky analysis demonstrated that the remarkably enhanced photocatalytic decolorization rate was ascribed to the stronger reduction potential of CIS with the mixed ZB/WZ phases and the redox potential difference between the ZB and WZ phases, leading to a good oxidation ability and charge separation. The results indicated that O₂^- was the main reactive specie in this study, and this study provided a potential photocatalyst in the treatment of dye wastewater.

One pot solvent assisted syntheses of Ag3SbS3 nanocrystals and exploring their phase dependent electrochemical behavior toward oxygen reduction reaction and visible light induced methanol oxidation reaction

A huge variety of silver based ternary sulfide semiconductors (SCs) have been considered for the sustainable advancement of renewable energy sources. Herein, we have synthesized two important classes of newly emerging semiconductor nanocrystals (NCs) Ag3SbS3 (SAS), i.e. hexagonal and monoclinic by simply tuning the solvent polarity, of which the second one has been synthesized in a phase pure NC for the first time by the thermal decomposition of silver and antimony based dithiocarbamate (∼N-CS2-M) complexes. Interestingly, these two systems exhibit two different semiconducting (SC) properties and band gaps; hexagonal SAS has a p type (Eg ∼ 1.65 eV) whereas monoclinic SAS has an n type (Eg ∼ 2.1 eV) character. For the first time ever we have designed a reducing working electrode (i.e. cathode) by modifying the rotating disc electrode (RDE) with hexagonal SAS that exhibits excellent electrochemical oxygen reduction reaction (ORR) activity (Eonset = 1.09 V vs. RHE and average number of electron transfer: 3.89) comparable to that of the highly expensive Pt/C (Eonset = 0.88 V vs. RHE and average number of electron transfer: 3.92). Density functional theory (DFT) investigation confirms the corroborations of experimental data with theoretical implications. In addition, the electrode fabricated from monoclinic SAS acts as an efficient photoanode which exhibits higher photoelectrochemical (PEC) methanol oxidation reaction (MOR) activity under illumination in alkaline medium compared to that of standard TiO2 grown on an indium tin oxide (ITO) coated glass slide. On illumination, the relative photocurrent density at the onset potential has been obtained to be 845 which is a very significant experimental output with respect to any other TiO2 or Pt@TiO2 based photocatalysts for this application. The physicochemical stability and reusability of both materials were supported by 50 hours of extended electrochemical chronoamperometric measurements and powder XRD and the TEM analyses after electrocatalysis. This study explores a possible pathway for designing simple and less expensive but catalytically efficient silver based ternary sulfide NC systems for developing an SC material to reduce the energy crisis in the near future.

NIR triggered PLGA coated Au-TiO2 core loaded CPT-11 nanoparticles for human papillary thyroid carcinoma therapy

MDR (multi-drug resistance) is one of the significant deterrents of effective chemotherapy for malignant growth. One of the powerful ways to deal with defeat of the MDR is to utilize inorganic nanoparticle-intervened tranquilize conveyance to build the medication aggregations in cancerous growth cells. In this work, we have developed the presentation that is accurately made of medication conveyance framework dependent on the TiO₂ nanoparticles stacked CPT-11 to defeat the thyroid malignancy cells. The synthesized nanoparticles are characterized by spectroscopy methods (UV–vis, XPS, SEM, TEM, and DLS). The TEM results suggested that the shape of PLGA-Au-TiO₂@CPT-11 of nanoparticles is ∼250 nm. After successful synthesis, we have evaluated the MTT of PLGA-Au-TiO₂@CPT-11 nanoparticles with and without NIR radiations. Further, the morphological changes were observed using various biochemical stainings, such as acridine orange and ethidium bromide (AO–EB) and nuclear staining through Hoechst-33258. Also, migration and cell invasion were examined. The results show that these PLGA-Au-TiO₂@CPT-11 and PLGA-Au-TiO₂@CPT-11 + NIR nanoparticles exhibited promising antimetastatic property and reduced the cell invasion activity in B-CPAP and FTC-133 thyroid cancer cell lines. Based on the above findings, these PLGA-Au-TiO₂@CPT-11 and PLGA-Au-TiO₂@CPT-11 + NIR nanoparticles can be used as a promising candidate for the malignant thyroid cells.

Solar light harvesting with multinary metal chalcogenide nanocrystals

The paper reviews the state of the art in the synthesis of multinary (ternary, quaternary and more complex) metal chalcogenide nanocrystals (NCs) and their applications as a light absorbing or an auxiliary component of light-harvesting systems. This includes solid-state and liquid-junction solar cells and photocatalytic/photoelectrochemical systems designed for the conversion of solar light into the electric current or the accumulation of solar energy in the form of products of various chemical reactions. The review discusses general aspects of the light absorption and photophysical properties of multinary metal chalcogenide NCs, the modern state of the synthetic strategies applied to produce the multinary metal chalcogenide NCs and related nanoheterostructures, and recent achievements in the metal chalcogenide NC-based solar cells and the photocatalytic/photoelectrochemical systems. The review is concluded by an outlook with a critical discussion of the most promising ways and challenging aspects of further progress in the metal chalcogenide NC-based solar photovoltaics and photochemistry.

Single source precursor driven phase selective synthesis of Au–CuGaS2 heteronanostructures: an observation of plasmon enhanced photocurrent efficiency

Coupling of metallic Au with CuGaS₂, synthesized from single molecule precursor [Ga(acda)₃Cu(PPh₃)₂]NO₃, results Au–CuGaS₂ heterostructure which shows remarkably high photocurrent response compared to CuGaS₂.