Small Nanorods Research Articles

Sustainable fabrication of dimorphic plant derived ZnO nanoparticles and exploration of their biomedical and environmental potentialities

Although, different plant species were utilized for the fabrication of polymorphic, hexagonal, spherical, and nanoflower ZnO NPs with various diameters, few studies succeeded in synthesizing small diameter ZnO nanorods from plant extract at ambient temperature. This work sought to pioneer the ZnO NPs fabrication from the aqueous extract of a Mediterranean salt marsh plant species Limoniastrum monopetalum (L.) Boiss. and assess the role of temperature in the fabrication process. Various techniques have been used to evaluate the quality and physicochemical characteristics of ZnO NPs. Ultraviolet–visible spectroscopy (UV–VIS) was used as the primary test for formation confirmation. TEM analysis confirmed the formation of two different shapes of ZnO NPs, nano-rods and near hexagonal NPs at varying reaction temperatures. The nano-rods were about 25.3 and 297.9 nm in diameter and in length, respectively while hexagonal NPs were about 29.3 nm. The UV–VIS absorption spectra of the two forms of ZnO NPs produced were 370 and 365 nm for nano-rods and hexagonal NPs, respectively. FT-IR analysis showed Zn–O stretching at 642 cm−1 and XRD confirmed the crystalline structure of the produced ZnO NPs. Thermogravimetric analysis; TGA was also used to confirm the thermal stability of ZnO NPs. The anti-tumor activities of the two prepared ZnO NPs forms were investigated by the MTT assay, which revealed an effective dose-dependent cytotoxic effect on A-431 cell lines. Both forms displayed considerable antioxidant potential, particularly the rod-shaped ZnO NPs, with an IC50 of 148.43 µg mL−1. The rod-shaped ZnO NPs were superior candidates for destroying skin cancer, with IC50 of 93.88 ± 1 µg mL−1 ZnO NPs. Thus, rod-shaped ZnO NPs are promising, highly biocompatible candidate for biological and biomedical applications. Furthermore, both shapes of phyto-synthesized NPs demonstrated effective antimicrobial activity against various pathogens. The outcomes highlight the potential of phyto-synthesized ZnO NPs as an eco-friendly alternative for water and wastewater disinfection.

Visible-light‑sensitive AgCu nanocomposites for sustainable inactivation of virus

The coronavirus disease 2019 (COVID-19) caused a large number of deaths and serious economic losses. Safety precautions and effective measures are urgently demanded to control the virus spread in public places. Owing to the longevity of the viruses in the aerosols and surfaces, sustained nanomaterials with efficient antiviral abilities during both daytime and night appear to be a promising way to control virus spread. Here, AgCu nanocomposites, which are outstanding antibacterial and antiviral elements, including Ag2Cu2O3 and AgCuO2, have been successfully prepared via a simple co-precipitation method for inactivation of model Qbeta (Qβ) bacteriophage. Notably, Ag2Cu2O3 has uniform nanorods morphology with a width of 50–100 nm and a length of 200–500 nm, regular elemental states of Cu2+ and Ag+, and good visible light response. Instead, AgCuO2 has more complex elemental states of Cu2+, Ag+, and Ag3+, including morphology with large particles of 500–1000 nm surrounded by small nanorods and nanoplates. Density functional theory (DFT) calculations showed that Ag2Cu2O3 has a lower work function than AgCuO2, indicating the charges can be better released from the surface. The accumulated surface charge can bind to the virus to inactivate it. As a result, Ag2Cu2O3 shows outstanding antiviral properties with a 6-log reduction (99.9999 %) of Qβ phage after 45 min contact under dark condition, and the activity can be further promoted to 7.5-log inactivation of Qβ phage after the same time contact under visible light irradiation, revealing its potential to sustainably prevent viruses spread in indoor environments.

Exploring Rotational Diffusion with Plasmonic Coupling.

Measuring the orientation dynamics of nanoparticles and nonfluorescent molecules in real time with optical methods is still a challenge in nanoscience and biochemistry. Here, we examine optoplasmonic sensing taking the rotational diffusion of plasmonic nanorods as an experimental model. Our detection method is based on monitoring the dark-field scattering of a relatively large sensor gold nanorod (GNR) (40 nm in diameter and 112 nm in length) as smaller plasmonic nanorods cross its near field. We observe the rotational motion of single small gold nanorods (three samples with about 5 nm in diameter and 15.5, 19.1, and 24.6 nm in length) in real time with a time resolution around 50 ns. Plasmonic coupling enhances the signal of the diffusing gold nanorods, which are 1 order of magnitude smaller in volume (about 300 nm3) than those used in our previous rotational diffusion experiments. We find a better angular sensitivity with plasmonic coupling in comparison to the free diffusion in the confocal volume. Yet, the angle sensitivity we find with plasmonic coupling is reduced compared to the sensitivity expected from simulations at fixed positions due to the simultaneous translational and rotational diffusion of the small nanorods. To get a reliable plasmonic sensor with the full angular sensitivity, it will be necessary to construct a plasmonic assembly with positions and orientations nearly fixed around the optimum geometry.

Branched ZnFe2O4 nanorods grown via chemical spray pyrolysis technique for chemiresistive xylene gas sensor

In this work, we used a chemical spray pyrolysis technique to deposit zinc ferrite (ZF) thin films at different substrate temperatures to study xylene (C8H10) gas sensing properties. The focus is on the detection of xylene, a volatile organic compound (VOC) that is harmful to human health. It was found that the concentration of hazardous xylene gas was below the exposure limit. The substrate temperature has a notable impact on the sensor's performance, and ZF exhibits promise for discerning xylene selectively at 200 °C operating temperature. The results indicate that the ZF film deposited at 225 °C (ZF-B) exhibited a significant response (S = 47.4%) to a 50-ppm xylene concentration. Further analysis illustrates that the film substrate temperature deposited at 225 °C can have a unique morphology including thin branched rods, small nanorods with high surface area and roughness. These features contribute to enhanced sensing response by creating more active centers for gas molecule interactions. The stability test over 125 days indicates that the ZF-B film acts effectively as a xylene gas sensor, emphasizing the effectiveness of ZF thin films in detecting xylene in an air environment.

Emergence of a Low-Energy Peak in the Smoothed Absolute Value Circular Dichroism Spectra of Small Helical Gold Nanorods.

We calculate, using time-dependent density functional theory, absorption and circular dichroism (CD) spectra for a series of small helical gold nanorod structures with a width of 0.6 nm and length increasing from 0.7 nm for Au24 to 1.9 nm for Au56. For a low-energy window, ranging from 1.7 to 4.1 eV, broadening the lines in the absorption spectra results in a low energy peak which previous studies have identified as the (localized) plasmon resonance. As expected, the absorption peak position of the plasmon resonance systematically redshifts as the length of the nanorod increases. However, trends in the CD and straightforwardly broadened CD spectra are more difficult to discern. We introduce the idea of an absolute value CD spectrum and show that broadening the lines results in a low energy peak that has not previously been reported. The peak position systematically redshifts as the length of the nanorod increases but over a significantly smaller range than that for the absorption spectrum.

Microwave-assisted synthesis of zinc oxide nanoflowers for improving the rheological and filtration performance of high-temperature water-based drilling fluids

Zinc Oxide (ZnO) nanostructures have proved useful across a wide range of applications like medical technology, electronics, sulfur removal as well as microbial growth control. In the petroleum industry, ZnO nanostructures have been widely researched for application in Drilling Fluids. ZnO has been previously reported to work excellently in enhancing the electrical and thermal properties of water-based drilling fluids (WBDFs). However, the role of morphological features of the nanostructures in influencing the properties of bentonite-laden WBDFs is less understood. In this work, ZnO nanostructures were synthesized under microwave irradiation which resulted in different shapes like rods and flowers. The effect of microwave power and time was observed with Field Emission Scanning Electron Microscopy (FE-SEM) and Dynamic Light Scattering (DLS), and a suitable synthesis criterion was selected for achieving the smallest complex ZnO nanoflowers. These nanoflowers were further characterized for functional group and structural identification. Bentonite/Polymer Nanofluids were prepared and tested for properties like rheology, API, and HPHT filtration before and after thermal aging at 150 °C. The results show ZnO nanoflowers in WBDFs have excellent filtration control ability with ∼56% reduction in HPHT filtrate volume and can impart a flat-line rheological profile. Also, the breaking of nanoflowers into smaller nanorods and some further textural changes is predicted to enhance the stability of the WBDFs due to better dispersion and compact mud cake formation. The study shows that the morphological features of metal oxide nanostructures can be controlled with microwave irradiation and play an effective role in controlling the properties of bentonite/polymer WBDFs.

Unleashing the power of sunlight: Bi2O3/Sb2S3 photocatalysis for sustainable wastewater remediation of Tetracycline and Rhodamine-B

The use of heterojunction photocatalysts for pollutant decomposition has garnered significant interest in mitigating water contamination and environmental pollution. Our present study focuses on synthesizing Bi2O3/Sb2S3 heterojunction photocatalyst having variable mole ratios by employing a hydrothermal technique. Loading Sb2S3 onto Bi2O3 enables broad-spectrum solar light absorption, efficient segregation of charges, and enhanced surface area, which are excellent traits for photocatalysis. Both Bi2O3 and Sb2S3 showed nano-rod type morphology, while Sb2S3 was present as smaller nano-rods and Bi2O3 as larger ones. The photocatalytic performance of this heterojunction photocatalyst was examined using Rhodamine-B (RhB) and Tetracycline (TC) under solar light illumination for 120 min. Remarkable decomposition efficiency was achieved, with a 98.2% degradation rate observed for RhB having a rate constant of 0.03149 min−1. Similar experiments were conducted using other light sources as well, such as visible light and UV light. However, only 83% and 69% RhB degradation rates were attained with visible and UV light, respectively, indicating that natural sunlight is the superior light source for our catalyst. A 91.5% degradation rate was achieved for TC with the rate constant of 0.01749 min−1, in the presence of sunlight for 120 min. A small amount (0.3 g/L) of 1:3 Bi2O3/Sb2S3 (13BOSBS) photocatalyst was enough to bring such a good result. The photocatalytic activity of our catalyst, that is, 98.2% RhB degradation, is much higher than that of commercially available TiO2–P25 powder, as the latter only achieved 52% RhB degradation. The pH at which the surface of Bi2O3/Sb2S3 has a zero charge (pHpzc) was determined to be 5.37 and the maximum decomposition of RhB was achieved at pH 7. Reusability tests verified the remarkable stability of this catalyst, with about 74.4% of RhB degradation still present after seven consecutive cycles. Scavenger experiments highlighted the crucial role of •OH radicals in the photodecomposition mechanism, as the incorporation of DMSO significantly influenced the photocatalytic efficiency of the 13BOSBS composite, leading to a notable decrease to 37.5% in RhB degradation. For the RhB dye, the 13BOSBS catalyst demonstrated remarkable 90.2% and 85% reductions in COD and TOC, respectively. The commercially available TC powder substantially reduced 84% in COD and 80% in TOC, whereas there was a 78% reduction in COD and 73% in TOC for TC tablets. The degradation of the contaminants was followed by the formation of simpler intermediates, which were discovered using the GC-MS approach. Owing to its excellent attributes and simple synthesis method, the fabricated heterojunction offers a promising solution to prevent the persistent buildup of harmful toxic pollutants in industrial wastewater systems.

Synthesis of small-sized gold nanorod using catechol as a reducing agent

Facile preparation of small gold nanorod with controllable and large surface plasmon resonance band is of great value for applications in especially the biomedical and sensing fields. In this work, we propose that without addition of additive to complicate the experimental system catechol of a very weak reducibility can be used as reducing agent for seed-mediated synthesis of gold nanorod. Under a temperature of 40 °C and a catechol concentration of 17.5 mM, monodisperse gold nanorod with a high shape yield, a largest plasmon wavelength of 918 nm, and especially a small diameter of 9.8 nm can be acquired simultaneously. A good tune over the plasmon wavelength is also shown by varying the amount of silver ion. Besides, the effects of experimental parameters including silver ion, cetyltrimethylammonium bromide, gold seed and catechol have also been carefully studied, and the morphological and structural evolutions of the particle have been discussed based on reported growth mechanism.

ZnO nanorod incorporated nematic liquid crystal for high multiplexing and high refresh rate displays

Zinc oxide nanorods incorporated in nematic liquid crystal matrix (NLC) are observed to improve physical properties of NLC and its device parameters, especially, for displays. In this article, we present the results of effect of incorporation of zinc oxide nanorods of various sizes but similar aspect ratio on physical properties of NLC. Zinc oxide nanorods (ZR) of similar aspect ratio (4–5) but different sizes (diameter: length) abbreviated as., ZR1 (10:50 nm), ZR2 (50:200 nm) and ZR3 (1:5 μm) are synthesized. Nanocomposites of synthesized nanorods with wide temperature range NLC are prepared. Smaller nanorods (ZR1) are expected to form chain like structures in host NLC matrix leading to softening of order parameter at the isotropic-nematic (I–N) transition. As the size of the nanorods increases the discontinuity of order parameter at I–N transition is observed to increase. Enhancement of dielectric anisotropy as well as birefringence which in turn indicates increase in the order parameter of the system is observed with the incorporation of zinc oxide nanorods. Reduction of threshold voltage, electro-optic response time and bulk ac conductivity and enhanced bend to splay elastic constant ratio of the nanocomposite samples as compared to pure NLC is observed with the incorporation of ZR in host NLC. Observed results show that nanorods of size ∼ 50: 200 nm are the most suitable to be incorporated in NLC for high multiplexing display devices.

Curcumin-capped gold nanorods as optical sensing platform for sequence specific detection of DNA based on their self-assembly

We are reporting curcumin-induced gold nanorods as an optical sensing platform for the detection of sequence-specific DNA target through their self-assembly. The combined effect of eco-friendly reducing agent (i.e., curcumin) and silver nitrate in a basic medium (i.e., pH 10) has been attributed for the formation of small gold nanorods (AuNRs) having approximate length and diameter i.e., 19.7 ± 0.8 nm and 6.0 ± 0.5 nm, respectively, and lower longitudinal surface plasmon resonance (SPR) enable to detect and analyse different biomarkers. Further, for evaluating cellular uptake of as-synthesized AuNRs, the cytotoxicity study has been carried out by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay on A549 cells and HEPG2 cell lines, respectively, and shown approximately similar cytotoxicity. Interestingly, as-synthesized optically and electronically active AuNRs based nanobiosensing platform enable to detect sequence-specific DNA targets with low level of detection limit i.e., LOD 8.6 ± 0.15 pM for complimentary target (CT) DNA with higher sensitivity and better selectivity. Finally, this study is suggesting a simplistic bio-mediated approach of tuning the shape and size of AuNRs for sensitive, selective and reliable nanobiosensing platform for sequence-specific DNA detection related to cancer cells.

Synthesis of Ta2O5 by introducing graphene quantum dot with excellent photocatalytic performance for degradation of tetracycline

Wide band gap, weak adsorption ability, poor electronic conductivity and insufficient charge transportation limit the applications of Ta2O5 in photodegradation of antibiotics. The paper reports synthesis of Ta2O5 photocatalyst by introducing glycine-functionalized graphene quantum dot (GGQD). The introduction of GGQD effectively prevents the hydrolysis of Ta(V) and finally leads to the formation of small Ta2O5 nanorods. The modification of graphene sheets on the Ta2O5 surface enhances the adsorption towards tetracycline. The presence of Ta4+ self-doped oxygen vacancy narrows the band gap of Ta2O5, optimizes the band position and creates new defect energy level. These improve the light absorption capacity to visible light and promotes the photogenerated charge transfer. The graphene as electron trap suppresses the recombination of photogenerated charge carriers. The graphene as light sensitizer expands the absorption to visible light. The synergy of these multiple structure engineering realizes an excellent photocatalytic performance of Ta2O5 for solar-light driven tetracycline photodegradation. The photodegradation efficiency of 60 min solar-light irradiation is 6.6 times higher, apparent kinetic constant is 19.3 times higher and photocurrent density is 13.4 times over Ta2O5. The study also paves an avenue for construction of metal nanomaterials with desirable photoelectric properties in catalysis, energy storage and conversion and sensing.

Sunlight propelled two-dimensional nanorobots with enhanced mechanical damage of bacterial membrane

Bacterial pollution in water sources poses a serious threat to human health and causes a water crisis. To treat it efficiently and ecologically, many studies have explored the antibacterial properties of two-dimensional nanomaterials in water, but their static antibacterial modes limit their effectiveness. In this work, we designed a facile and effective antibacterial nanorobots by loading super small gold nanorods (sAuNR) onto the surface of MXene nanosheets (MXene@sAuNR). The plasmon resonance effect of sAuNR can enhance the optical absorption cross section of the nanorobots, thereby improving their motion ability under irradiation and then causing cell membrane mechanical damage to bacteria. Our research proved that nanorobots with good optical driving characteristics displayed gratifying antibacterial properties even at ultra-low concentration as 5 µg/mL within 30 min. Furthermore, the nanorobots showed satisfactory antibacterial efficiency in real river samples under sunlight irradiation. These nanorobots presented in this study provides valuable insights towards designing self-energy collection and self-driving antibacterial materials that overcome the shortcomings of conventional static antibacterial methods. As sunlight is the cheapest and natural light source, these nanorobots have opened an effective and sustainable way for large-scale treatment of bacterial pollution in water.

Significance of microstrain in impacting band gap and photoluminescence behavior of Ce-doped ZnO thin films deposited via sol-gel process

The purpose of this study is to analyse the importance of micro-strain in affecting the band gap and photoluminescence (PL) intensity of sol-gel-spin-coated Ce-doped ZnO thin films on glass slides. The presence of the (100) plane in the fabricated thin film was discovered using x-ray diffraction thereby indicating the presence of strongly orientated monocrystalline ZnO hexagonal wurtzite phase. On doping with Ce, the micro-strain in the ZnO thin films changed from (2.49–4.84) × 10–3, and the crystallite size ranged from 26.23 to 43.03 nm. UV-visible spectroscopy revealed that the optical transparency of the undoped and Ce-doped ZnO films was between 60 to 85 percent, however the doped films’ absorption dip was slightly shifted from 378 to 380 nm. For Ce-doped ZnO thin films, the increase in band gap values determined using Tauc’s plot was in the range of 3.19 to 3.44 eV. No change in the peak of UV emission was visible in the PL emission spectra after Ce doping. The micro-strain brought on by doping ZnO with Ce controlled the decrease in PL intensity. On doping with Ce up to 3 at.%, PL intensity and micro-strain both reduced, then climbed till Ce 5 at.%, and ultimately declined when the Ce content was 6 at.%. According to studies using scanning electron microscopy, the undoped ZnO film morphology was characterised by spherical particles with rod-like growth structures. For 1, 2, 5, and 6 at.% Ce-doped ZnO thin films, this structure was changed to a nanorod-like structure with small nanorods attached to a long rod. But lengthy chain linkage structures were found in the event of 3 at.% Ce doping. The preceding results are discussed from a doping perspective.

Cytotoxicity of mini gold nanorods: intersection with extracellular vesicles.

It is well-known that there are size- and shape-dependencies to nanoparticle uptake and processing by living cells. Small gold nanorods have shown to exhibit low toxicity and high clearance rates when compared to larger ones, making smaller particles more desirable for biomedical applications. In this study gold mini-rods (approximately 9.5 × 23, 8 × 26, and 6 × 26 nm, corresponding to aspect ratios 2.5, 3.2 and 4.1) and gold nanospheres (15.6 nm average diameter) were synthesized, and wrapped with cationic and anionic polyelectrolytes. This library of colloidally stable nanomaterials was exposed to human dermal fibroblasts at the relatively low concentration of 1 nM for each nanoparticle type. The cytotoxic profile of these nanoparticles and their influence on the small extracellular vesicles released by the cells was assessed. It was observed that although the nanoparticles were found in vesicles inside the cells, the cell viability, the mitochondrial membrane potential and levels of reactive oxygen species were not markedly affected by the mini gold nanorods. The production of extracellular vesicles by the cells was unaffected by gold nanoparticle exposure; moreover, no gold nanoparticles were observed in extracellular vesicles in the exosomal size range. Taken together, these results suggest that these mini gold nanorods are suitable for a wide range of cellular applications for relatively short-term studies.

Photothermal effects of gold nanorods in aqueous solution and gel media: Influence of particle size and excitation wavelength.

Gold nanorods (GNRs) have emerged as the most efficient photothermal agent in cancer therapy and photocatalysis. Understanding the influence of the surrounding medium, particle size, and excitation wavelength is critical to optimising the photothermal conversion rate. Here, three pairs of large and small gold nanorods of different aspect ratios and their heat generation under laser radiation at on and off surface plasmon resonance wavelengths in aqueous solution and gel-like media are investigated. In the aqueous solution, the temperature rise of the large gold nanorods is more than with small gold nanorods at resonance excitation. In contrast to the large gold nanorods (LGNRs), the small gold nanorods (SGNRs) were less sensitive to excitation wavelength. At off-resonance excitation, the temperature rise of the SGNRs is larger than that of the LGNRs. In the agarose gel, the photothermal effect of the SGNRs is greater than LGNRs excited at the wavelength near their solution phase longitudinal surface plasmon resonance wavelength. The temperature increase of LGNRs in gel is significantly less than in aqueous solution. These findings suggest that SGNRs could be more beneficial than the LGNRs for photothermal applications in biological systems and provides further insight when selecting GNRs.

Void space and secondary oriented attachment mechanisms in cerium oxide nanorods

Two new processes occurring during nanorod annealing of ceria are disclosed, both belonging to the wider “oriented attachment” (OA) scheme of crystal growth, which commonly drives nanoparticles growing into nanorods. The first new process is an inversion of the standard OA, where the usual solid particles are replaced by well-facetted shape-equilibrated voids inside larger single crystals. The internal facetted voids are then found to aggregate during dry heat treatment into rod-shaped elongated voids growing eventually towards nanotubes. For the case of CeO2, a perfect equivalence is found between positive OA, involving cuboctahedral {111}/{100} nanoparticles turning into {110}/{100} nanorods, and negative or void space OA, where cuboctahedral voids turn into negative tubular rods of same indexing. The second OA process (“secondary OA”) concerns aggregation of small nanorod segments into larger, double, or quadruple sized nanorods, with perfection of alignment and bonding exceeding simple van der Waals forces. Eventually, the new rods merge into single crystal grain boundary–free larger rods, but with an external shape, including double-ended rods, indicating their origin from several rods. Both processes are found on identical samples and occur in parallel.

Structural engineering of α-MnO2 cathode by Ag+ incorporation for high capacity aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) are considered as renewable alternatives to lithium-ion batteries (LIBs) for large-scale energy storage applications due to their intrinsic safety, cost-effectiveness, and environmental friendliness. The design and development of cathode materials are the main challenges to realizing the full potential of aqueous ZIBs. Here, we design Ag0.4Mn8O16 nanorods by structural engineering of α-MnO2 via Ag + incorporation for ZIBs cathode material. The sliver species are well dispersed in the tunnels of α-MnO2, which results in higher surface area, smaller nanorods, and oxygen vacancies in the Ag0.4Mn8O16 structure. Along with the redox activity of Ag+, reversible co-insertion/extraction of H+/Zn2+ ions in Ag0.4Mn8O16 followed by the formation of ZnxAg0.4-xMn8O16/MnOOH are observed. The generation of in-situ silver matrix greatly enhances the electronic conductivity, which, together with the reversible Ag0.4Mn8O16 structure, reveals an excellent electrochemical performance such as excellent rate capability, the high specific capacity of 306 mAh g−1 at 0.1 A g−1, and long-term cycling life over 800 cycles at 1 A g−1 compared to α-MnO2 (227 mAh g−1 at 0.1 A g−1). This work provides the design of cathode materials and the corresponding energy storage mechanism options for rechargeable aqueous ZIBs.

Thiolated hyaluronic acid and catalase-enhanced CD44-targeting and oxygen self-supplying nanoplatforms with photothermal/photodynamic effects against hypoxic breast cancer cells

Photothermal and photodynamic therapies (PTT/PDT) have been widely accepted as noninvasive therapeutic methods for cancer treatment. However, tumor hypoxia and insufficient delivery of photoactive compounds to cancer cells can reduce the efficacy of phototherapy. Herein, we first synthesized thiolated hyaluronic acid (THA) and then conjugated it with catalase (CAT) onto chlorin e6 (Ce6)-adsorbed small gold nanorods (Ce6@sAuNRs) with near-infrared (NIR)/visible light activated photothermal/photodynamic effects. The conjugation of THA and CAT on Ce6@sAuNRs resulted in a red-shift of the longitudinal LSPR absorption band of sAuNRs up to 1000 nm and maintained the excellent enzymatic activity of catalase. Modification of Ce6@sAuNRs with THA resulted in efficient internalization of the nanocomposite into MCF-7/ADR multidrug-resistant (MDR) breast cancer cells (CD44+), thereby significantly enhancing the intracellular accumulation of the photosensitizer Ce6. CAT endows Ce6@sAuNRs with self-supporting oxygen production, which enables them to efficiently generate singlet oxygen (1O2) under 660 nm laser irradiation and enhances the photodynamic effect against hypoxic breast cancer cells. The results highlight the prospect of this novel multi-functional nanoplatform integrating active biological macromolecules (THA and CAT) into photosensitizer/photothermal gold nanocomposites in overcoming the limitations of hypoxic MDR breast cancer cell treatment.

Solar light driven photoelectrochemical water splitting using Mn-doped CdS quantum dots sensitized hierarchical rosette-rod TiO2 photoanodes

Herein we investigated the photoelectrochemical performance of manganese (Mn) doped cadmium sulfide (CdS) quantum dots (QDs) decorated onto the surface of hierarchical double-layered rosette-rod titanium dioxide (TiO2) photoanode. The rosette-rod TiO2 architectures are synthesized by two steps hydrothermal process while Mn-doped CdS QDs deposition is taken out by successive ionic layer adsorption and reaction (SILAR) approach. Two different kinds of structures exist simultaneously in rosette-rod TiO2, one-dimensional TiO2 nanorod arrays present at the bottom, while the upper three-dimensional nano rosette consists of small TiO2 nanorods as building units. Photoelectrochemical performance of the as-prepared photoanodes are explored in terms of photocurrent density and applied biased to photon conversion efficiency by varying Mn concentration and the number of SILAR cycles to find the best performing photoanodes. Linear sweep voltammetry results show that 35 mM shows the maximum photo-current density of 2.12 mA cm−2 at 1.23 VRHE with a maximum photoconversion efficiency of ∼1.61% at 0.4 VRHE, while 8 numbers of SILAR cycles shows the highest photo current–density of 2.73 mA cm−2 at 1.23 VRHE and maximum photoconversion efficiency of 2.19% at 0.2 VRHE.

Photothermal effects in small gold nanorod aggregates for therapeutic applications

Proximity of the metal nanoparticles enhance the plasmonic coupling and shifts the resonance. This article presents a numerical study of the photothermal effect in aggregates of small gold nanorods considering the ordered as well as random aggregates. In the ordered aggregates, there is lateral coupling which causes blueshifts in the plasmonic resonance, while in the random aggregates, there are redshifts in the plasmonic resonance. The plasmon response of latter could be tailored up to the second infrared biological therapeutic window. It has been observed that the aggregates show higher absorption power, and therefore, higher temperature rise compared to the single gold nanorod or monodispersive nanorods. The absorption resonance peak position of the random aggregate depends on the incident and polarization angles of the incident light. The aggregation of the nanoparticles often inherently occurs in the biological medium which affects the photothermal process. This study helps to understand the photothermal heating of nanoparticle aggregates and the use of the optimal light source concerning the absorption peak of the aggregates suspension for therapeutic uses.