Secondary Nanostructures Research Articles

Vertical and porous MoS2-CoS2 heterojunction nanosheet arrays as highly efficient bifunctional electrocatalysts for oxygen and hydrogen evolutions

Highly efficient water electrolytic agents are restricted by the lack of cheap and Earth-abundant catalysts that can manipulate at unharsh conditions and be prepared with a simple procedure. Here, hierarchically vertical and porous MoS2-CoS2 heterojunction nanosheet arrays are designed and fabricated. The MoS2-CoS2 nanosheets are composed of ultrasmall nanocrytallites with the dimension of ∼62 nm. This special and novel architecture presents synergistic properties to create excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), where high density active sites generated by ultrasmall nanocrytallites with heterostructures, and the vertical and porous structure accelerates electrolyte transport with luxuriant channels while this hierarchically collaborative framework guarantees completely exposed active sites to electrolytes. This electrode shows low overpotentials of 295 and 103 mV at 10 mA cm−2, small Tafel slopes of 70 and 78 mV dec−1, and long stability for OER and HER, respectively. This work indicates that vertical and porous heterojunction nanosheet arrays with hierarchically ultrasmall secondary nanostructures are a promising catalyst for widespread application.

Novel Synthesis of 3D Mesoporous FePO4 from Electroflocculation of Iron Filings as a Precursor of High-Performance LiFePO4/C Cathode for Lithium-Ion Batteries.

This study presents an economic and environmentally friendly method for the synthesis of microspherical FePO4·2H2O precursors with secondary nanostructures by the electroflocculation of low-cost iron fillers in a hot solution. The morphology and crystalline shape of the precursors were adjusted by gradient co-precipitation of pH conditions. The effect of precursor structure and morphology on the electrochemical performance of the synthesized LiFePO4/C was investigated. Electrochemical analysis showed that the assembly of FePO4·2H2O submicron spherical particles from primary nanoparticles and nanorods resulted in LiFePO4/C exhibiting excellent multiplicity and cycling performance with first discharge capacities at 0.2C, 1C, 5C, and 10C of 162.8, 134.7, 85.5, and 47.7 mAh·g-1, respectively, and the capacity of LiFePO4/C was maintained at 85.5% after 300 cycles at 1C. The significant improvement in the electrochemical performance of LiFePO4/C was attributed to the enhanced Li+ diffusion rate and the crystallinity of LiFePO4/C. Thus, this work shows a new three-dimensional mesoporous FePO4 synthesized from the iron flake electroflocculation as a precursor for high-performance LiFePO4/C cathodes for lithium-ion batteries.

An Overview of the Molten Salt Nanofluids as Thermal Energy Storage Media

The research in the field of the nanofluids has experienced noticeable advances since its discovery two decades ago. These thermal fluids having minimal quantities of nano-scaled solid particles in suspension have great potential for thermal management purposes because of their superior thermophysical properties. The conventional water-based nanofluids have been extensively investigated so far with emphasis in their improved thermal conductivity. A novel class of nanofluids based on inorganic salts has been developed in the last few years with the goal of storing and transferring thermal energy under high temperatures. These molten salt-based nanofluids can in general be recognized by an enhanced specific heat due to the inclusion of the nanoparticles. However, it should be emphasized that this does not always happen since this thermophysical property depends on so many factors, including the nature of the molten salts, different preparation methods, and formation of the compressed layer and secondary nanostructures, among others, which will be thoroughly discussed in this work. This peculiar performance has caused a widespread open debate within the research community, which is currently trying to deal with the inconsistent and controversial findings, as well as attempting to overcome the lack of accurate theories and prediction models for the nanofluids in general. This review intends to present an extensive survey of the published scientific articles on the molten salt nanofluids. Other important realities concerning the development and thermal behavior of the molten salt nanofluids, such as the stability over time of the nanoparticles dispersed in the molten salts, latent heat, viscosity, and thermal conductivity, will be reviewed in the current work. Additionally, special focus will be given to concentrated solar power technology applications. Finally, the limitations and prospects of the molten salts nanofluids will be addressed and the main concluding remarks will be listed.

Injectable heat-sensitive nanocomposite hydrogel for regulating gene expression in the treatment of alcohol-induced osteonecrosis of the femoral head.

For repairing lesions, it is important to recover physiological and cellular activities. Gene therapy can restore these activities by regulating the expression of genes in lesion cells; however, in chronic diseases, such as alcohol-induced osteonecrosis of the femoral head (ONFH), gene therapy has failed to provide long-term effects. In this study, we developed a heat-sensitive nanocomposite hydrogel system with a secondary nanostructure that can regulate gene expression and achieve long-term gene regulation in lesion cells. This nanocomposite hydrogel exists in a liquid state at 25 °C and is injectable. Once injected into the body, the hydrogel can undergo solidification induced by body heat, thereby gaining the ability to be retained in the body for a prolonged time period. With the gradual degradation of the hydrogel in vivo, the internal secondary nanostructures are continuously released. These nanoparticles carry plasmids and siRNA into lesion stem cells to promote the expression of B-cell lymphoma 2 (inhibiting the apoptosis of stem cells) and inhibit the secretion of peroxisome proliferators-activated receptors γ (PPARγ, inhibiting the adipogenic differentiation of stem cells). Finally, the physiological activity of the stem cells in the ONFH area was restored and ONFH repair was promoted. In vivo experiments demonstrated that this nanocomposite hydrogel can be indwelled for a long time, thereby providing long-term treatment effects. As a result, bone reconstruction occurs in the ONFH area, thus enabling the treatment of alcohol-induced ONFH. Our nanocomposite hydrogel provides a novel treatment option for alcohol-related diseases and may serve as a useful biomaterial for other gene therapy applications.

Effect of Micro-Dimple Geometry on the Tribological Characteristics of Textured Surfaces

The introduction of external surface features on mating contact surfaces is an effective method to reduce friction and wear between the contact surfaces. The tribological properties of the contact surfaces can be improved by controlling the geometrical parameters (shape, size, depth) of the surface texture effectively. In the present study, the tribological properties of Al6061-T6 cylindrical workpieces with various micro-dimple-texture geometries and an AISI 52100 steel stationery block are tested experimentally, in a rotating cylinder-on-pin configuration of the friction test. The dual-frequency surface texturing method is employed to create micro-dimple textures using a polycrystalline diamond tool. The effect of a hierarchical micro-dimple texture is then investigated under boundary lubrication conditions. Hierarchical micro-dimples, with an increase in length, show a lower friction coefficient under high load and sliding speed conditions. Secondary hierarchical nano-structures help in improving the tribological characteristics by generating an additional hydrodynamic lift effect.

Green synthesis, characterization of SnO2 3D microbars with surface 2D nanostructures and evaluation of electrical properties of PMMA-SnO2 hybrid nanocomposites

SnO2 3D microbars (L ∼ 10 µm × B ∼ 1 µm x T ∼ 1 µm) distributed with 2D nanostructures (D ∼ 20 - 50 nm x l ∼ few nm) were synthesized by green approach using Plectranthus amboinicus plant extract. Effect of calcination treatments on the morphological changes of both primary microbars and secondary nanostructures were investigated. Dense corrugated networks of secondary particles were observed in the freshly synthesized material. When subjected to a temperature of 200 °C the densely covered particles on the surface, separate to distinct nanostructures. On further rise of temperature up to 400 °C, nanostructure networks break to complete individual nanoparticles, along with mild fragmental damage of particles. Presence of functional groups and bandgap energy levels of 3D/2D SnO2 material was studied using Fourier Transform Infra-Red (FTIR) and UV-Visible (UV-Vis) spectroscopy, respectively. Bandgap energy level of 3.05 eV was observed at 400 °C and 3.06 eV was observed at other two conditions. Structural, morphological and elemental characterization of the material was studied by X-ray diffraction (XRD), Field Emission-Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-ray Analysis (EDAX) spectroscopy. Using Polymethyl methacrylate (PMMA) as matrix and 3D/2D SnO2 as the dispersed filler phase nanocomposite films were prepared. Effect of 3D/2D SnO2 loading on the alternating current (AC) conductivity of the nanocomposite films was investigated. Effect of frequency on AC conductivity, permittivity and loss factor of the composites were reported. The composites exhibited frequency dependent conductivity at lower frequencies and frequency independent conductivity at higher frequencies.

Nanoarchitectonic manganese-cobalt phosphide through zeolitic–imidazolate framework for efficient electrocatalysis in hydrogen evolution reaction

Nanostructured materials with unique structural properties have attracted the interest of researchers, because these materials are rich in active sites, offer enhanced ion transport, and are robust for application in electrochemical energy storage and conversion. However, the synthesis of nanocubes of morphological metal phosphides, especially secondary metal-supported metal phosphide nanostructures, is still under research, due to the generation of synergistic effects. In this article, we present a Mn–Co metal phosphide in a nitrogen-doped carbon matrix (MnCoP4 @NC), using zeolite imidazolate framework-67 (ZIF-67) nanocubes. The addition of the surfactant cetyltrimethylammonium bromide (CTAB) changes the morphology of dodecahedra to nanocubes during synthesis at room temperature. The ZIFs are then phosphided in a tube furnace at 450 °C in a nitrogen gas atmosphere. In addition, the electrochemical performance of the synthesized materials was investigated using the hydrogen evolution reaction (HER). The MnCoP4 @NC shows excellent electrocatalytic activity of 206 mV overpotential to reach 10 mA·cm−2 current density, as well as very good kinetic behavior and long-term stability up to a 25 h chronopotential run. The proposed material synthesis will support the development of nanoarchitecture materials for electrocatalyst-based energy applications.

A multifunction superhydrophobic surface with excellent mechanical/chemical/physical robustness

Superhydrophobic surfaces have many advantages in wetting fields. However, the lack of easyily production methods and limited mechanical/chemical/physical robustness remain the two most pertinent barriers to the scalability, large-area production, and widespread use of superhydrophobic materials. In this work, a mechanical/chemical/physical robustness superhydrophobic coating sample consisting of a regular array of square Cu mesh with secondary nano structures of polytetrafluoroethylene (PTFE) and SiO2 powders on the sidewalls is produced through a scalable and easyily production technique of the combination of hot-press sintering and subsquent spray-coating. The Cu mesh is used as a template to fabricate the grooves and bulges as the first-level roughness, and the SiO2 powder is maintained on the surface of the coatings to form two-level hierarchical structures, with both micro and nano structures firmly affixed by low-surface energy polymer binder (PTFE). For comparison, Cu mesh and Cu mesh/Cu sample are also produced. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and time-dependent apparent contact angle are used to examine the as-prepared materials. The corrosive solution, high temperature, UV irradiation, ultrasonic treatment, water drop hitting, sand drop impacting, multi-cycled sandpaper abrasion, tape-peeling test, and self-cleaning test was conducted to simulate the real-world damages. All of the armored superhydrophobic coating samples have an apparent water contact angle of more than 150°, as well as outstanding mechanical and chemical resilience. The salt spray test and mechanical behavior of the as-prepared samples revealed that the armored superhydrophobic coating sample has the lowest corrosion rate, the highest tensile strength, and the greatest elongation among these threee as-prepared samples, implying that it has the best anti-corrosion ability and mechanical property. This strategy might give guidance for the development of composite materials that need to retain mechanical/chemical/physical robustness in severe working conditions.

Design of gel-to-sol UCST transition peptides by controlling polypeptide β-sheet nanostructures

Creating stimulus-responsive materials solely by controlling polypeptide secondary nanostructures is challenging. We synthesized a methyl poly(ethylene glycol)-b-poly(O-benzyl-L-threonine) (mPEG-PBnLT) diblock copolymer that exhibited gel-to-sol UCST (Upper Critical Solution Temperature) transition behavior in an aqueous solution. The transition temperature window was easily adjusted by changing the copolymer concentration or length of the PBnLT block. Disassembly of the initial β-sheet nanoassemblies caused nanofibril transformation to spherical aggregates with increasing temperature, resulting in a gel-to-sol UCST transition. This result inspires a brand-new strategy for the structural design and functional control of materials. A novel thermoresponsive diblock copolymer of methyl poly (ethylene glycol)-b-poly (O-benzyl-L-threonine) was synthesized. The copolymer solutions exhibited gel-to-sol UCST transition behavior with temperature. The gel-to-sol transition was due to the disassembly of the initial β-sheet layered nanoassemblies that induced the transformation of self-organized morphology from nanosized fibrils to spherical aggregates.

Dual thermoresponsive mPEG-b-poly(O-benzyl-l-threonine acid) hydrogel based on β-sheet nano-structural disassembly and PEG dehydration

It is a challenging work to design novel responsive materials by controlling the secondary structure of polypeptide, especially β-sheet. We designed and synthesized a novel dual responsive diblock copolymer of methyl poly (ethylene glycol)-b-poly (O-benzyl-l-threonine) (mPEG-b-PBnLT). The copolymer solutions exhibited unusual and reversible gel-to-sol-to-gel transition behavior with temperature, and the transition temperature window could be easily adjusted by changing copolymer concentration or PBnLT block length. It was confirmed that low temperature gel-to-sol transition was due to the disassembly of the preliminary β-sheet layered nano-assemblies that induced the transformation of self-organized morphology from nanosized fibrils to spherical aggregates, while the high temperature sol-to-gel transition was ascribed to the dehydration of PEG segments. The disassembly of β-sheet structures was caused by the change in the polarity of the pendant benzyl ether bond of PBnLT block in water with temperature. This stimuli-responsiveness of secondary self-assembled nanostructures and the corresponding change in macroscopic phase transition inspires a brand-new strategy for structural design and functional control of polypeptide materials.

Electrospun TiO2‐Based Photocatalysts

Solar‐driven semiconductor photocatalysis shows great potential to solve growing energy and environmental crises. Electrospun TiO2 nanofibers (NFs) attract attention due to their chemical stability, nontoxicity, cheapness, large specific surface area, and porous structures. The unique unwoven nanofibrous network facilitates mass transportation compared with bulk materials. Electrospun TiO2 NFs are an ideal substrate for growing secondary nanostructures and constructing heterojunction photocatalysts. The hybrid heterojunctions show enhanced electron–hole separation, improved light absorption, effective activation of reactants, and therefore increased photocatalytic performance. Herein, the electrospinning principle and preparing tactics of electrospun TiO2 fibrous nanostructures including solid, hollow, and core/shell NFs are first described. The construction strategies of electrospun TiO2‐based heterojunctions by loading electron or hole cocatalysts and hybridizing secondary semiconductors to engineer catalytic active sites and steer charge carrier separation are outlined. Dopant‐induced increased light absorption and enhanced charge transfer of TiO2 NFs are discussed. Further, the applications of electrospun TiO2‐based photocatalysts for solar‐to‐chemical conversion and environmental remediation are elucidated. Finally, the challenges and perspectives for the development of electrospun TiO2‐based photocatalysts are underlined, which deepen a systematic understanding of the design and fabrication of more efficient electrospun NFs in the future.

A high-safety and multifunctional MOFs modified aramid nanofiber separator for lithium-sulfur batteries

High-level safety is the essential precondition for the future large-scale applications of the high-energy storage systems. In terms of the lithium-sulfur (Li-S) batteries, the low flash point and poor mechanical strength of the conventional polyolefin separator are the potential safety hazards to cause the fire and explosion in extreme environment. Herein, a thermotolerant and nonflammable hierarchical functional separator (Z-PMIA separator) is designed based on the poly(m-phenylene isophthalamide) (PMIA) membrane and the in-situ formed Co-containing zeolitic imidazolate framework ZIF-L(Co) secondary nanostructures. Benefiting from the feature of “Aramid” fibers and the special secondary ZIF-L(Co) nanostructures, the Z-PMIA separator not only guarantees high mechanical strength (suffering from a tensile strength of 15 MPa and a puncture force of 0.95 N) and remarkable thermal stability (no dimensional shrinkage even at 200 °C) but also effectively suppresses the polysulfide shuttle and lithium dendrite growth. As a result, the Z-PMIA separator delivers a high initial discharge capacity of 1391.2 mAh g−1 and a discharge capacity of 961.1 mAh g−1 after 350 cycles at 0.2C, with a slow capacity attenuation of 0.033% per cycle. Even under the conditions of high sulfur loading (9.23 mg cm−2) and low electrolyte/sulfur (E/S) ratio (8 mL g−1) or when running at a high temperature (80 °C), the Z-PMIA separator still enables a high charging/discharging performance, highlighting its promising commercial prospect for future high-safety and high-performance energy storage systems.

Modulated vibration texturing of hierarchical microchannels with controllable profiles and orientations

Hierarchical microchannels, which consist of the primary channel formation and superimposed secondary nanostructures, are attracting ever-increasing attention due to their unique capacity to enhance and modify the surface characteristics and functional performance. The mechanical machining methods for microchannel fabrication, such as micro-milling and diamond turning, can achieve high material removal rates without changing material properties. However, they have limited capacity to control the channel cross-section profiles and shapes due to the relative size between the channel dimension and tool geometry. This study proposes a new cutting-based approach for the fast and cost-effective fabrication of hierarchical microchannels with controllable profiles and orientations by utilizing modulated elliptical vibration texturing. The modulation motion is adopted to form the primary channel in an incremental approach, while the elliptical vibration texturing is utilized to create micro/nano-scale secondary textures. By controlling the tool modulation trajectory, hierarchical dimple arrays with controllable cross-section profiles are first demonstrated. Then, by programming the layout of dimples to adjust the overlapping ratio between each cut, channels can be formed with arbitrary cross-section profiles and orientations. The efficacy of the proposed process has been demonstrated through numerical simulation and experimental results. Hierarchical microchannels with straight and curving shapes, as well as different cross-section profiles (sinusoidal, triangular, trapezoidal), have been presented.

Hollow Li2SiO3 architectures with tunable secondary nanostructures and their potential application for the removal of heavy metal ions

Li2SiO3 is a potential new material for mitigating environmental issues such as greenhouse effect and wastewater treatment, but the high-quality failure and evolvable morphology limit have restricted its large-scale application. Herein, a high-quality hierarchically hollow-structured Li2SiO3 assembled by tunable secondary structures was precisely fabricated by an efficient green and facile hydrothermal method. The secondary structures, from nanosheets to belts, thorns, spinule and eventually to nanoparticles, accompanying the corresponding morphologies evolving from peony-like to chrysanthemum-like, urchin-like, waxberry-like and eventually to spherical structures, could be tuned by adjusting precursors’ Li/Si molar ratios. All of the obtained hollow Li2SiO3 structures were attributed to a common growth mechanism called inside-out Ostwald ripening. The as-prepared hollow Li2SiO3 structures were experimented as heavy metal adsorbents for the first time and exhibited excellent adsorption performance for all employed heavy metal ions (Cu2+, Mn2+ and Ni2+). Furthermore, as a case study, the obtained heavy metal-bearing Li2SiO3 architectures (Cu(OH)2@Li2SiO3, MnO(OH)2@Li2SiO3 and Ni(OH)2@Li2SiO3) inherited the primary hollow morphology, which endowed them with reusability as high-efficient adsorbents for methylene blue by color removal efficiency higher than 98%. This work lays the foundation for the development of an environmentally friendly “two birds with one stone” route of “remover of heavy metal ions to dye adsorbent,” which will be of great significance for the wastewater treatment.

Formation of Nanostructure and Tool Wear during Cutting Treatment of Titanium Alloy

Methods of the optical metallography, TEM, SEM-technique, tests for hardness and wear resistance are used to investigated the structural - phase transformation in metal blanks from alloy VT23 at cutting treatment in an interval of speeds 2...120 m/min are given. The patterns of interaction of dynamic plastic deformation and destructions on macro-, meso-, micro-and nanolevels are determined. It is shown that the formation in metal blank of modulated high-tensile secondary nanostructures promotes a heightening of a protective wearproofity of treated metal blank, but cutting edge, lowering a wearproofity, of the cutting tool.

Hydrothermally-grown nanostructured anatase TiO2 coatings tailored for photocatalytic and antibacterial properties

Low-temperature solution growth of TiO2 films provides unique surface functionalities for base materials that may not survive high processing temperatures. It involves multiple stages of crystal growth at various length scales. Having a fundamental understanding of the mechanisms involved in those stages is essential to obtain desirable functional performances. In this study, we prepared diverse anatase microstructures via a hydrothermal method, all of which start from homogeneous nucleation of the nanoparticles when precursor solution reaches above a critical saturation point. Depending on pH, concentration, temperature and ionic species of precursor solution, however, these primary nanoparticles evolve into different shapes of secondary nanostructures via aggregation of nanoparticles. Thin films of anatase TiO2 consisting of those secondary nanostructures, which have a [001]-texture with (004) surfaces exposed, exhibited the strongest photocatalytic as well as antibacterial properties.

Solvent evaporation driven entrapment of magnetic nanoparticles in mesoporous frame for designing a highly efficient MRI contrast probe

The present work reports a novel strategy of assembling maghemite (γ-Fe2O3) nanoparticles (NPs) in mesoporous silica host for developing a highly efficient MRI contrast probe. Shrinkage of hydrophobic environment due to the continuous evaporation of chloroform from Chloroform-in-Water emulsions pushes the hydrophobic γ-Fe2O3 NPs towards the hydrophobic pores of silica spheres resulting in a water soluble dense assembly structure. Mesoporous silica only with straight pores is found to be suitable for this particular entrapment process, while with curved and twisted pores, NPs are found to be seated on the surface only. So-developed assembly system has retained the superparamagnetic behaviour of its comprising NPs and exhibited high colloidal stability and biocompatibility. A significant enhancement in MRI transverse relaxivity to 386.2 mM−1 s−1 from 191.8 mM−1 s−1 of isolated primary γ-Fe2O3 NPs, has been obtained due to the strong magnetic field generated by the large number of NPs packed in the porous channels and consequent faster relaxation process. The fabrication strategy can be extended for the development of designed secondary nanostructures with new magnetic effects and physical properties.

Building High‐Density Au–Ag Islands on Au Nanocrystals by Partial Surface Passivation

AbstractAs an advanced level of control in colloidal synthesis, it is highly desirable to create secondary structures of nanocrystals in a controllable manner for collective properties. Of particular interest is the generation of nanoislands of plasmonic metals (Ag and Au) at a high density around their pre‐existing primary nanocrystals, which may produce abundant hotspots for surface‐enhanced Raman scattering (SERS). Often such secondary structures are difficult to be achieved by direct crystal growth because a conformal growth is favorable due to the lattice match of these metals. Here, this challenge is overcome by developing a partial surface passivation strategy which can effectively shift the crystal growth mode from the “Frank–van der Merwe” mode to the “Volmer–Weber” mode, giving rise to nanoislands as a secondary structure on Au nanocrystals. The key to this strategy is the modification of the Au surface with Ag and subsequent adsorption of iodide at the Ag sites. Further deposition of Au on the modified surface leads to the formation of well‐defined Au–Ag alloy islands of a high density on Au nanocrystals, which exhibit excellent SERS activity. This partial surface passivation strategy is fundamentally important and may inspire further endeavors in pursuit of novel secondary nanostructures and intriguing properties.

Anti-Reflectance Optimization of Secondary Nanostructured Black Silicon Grown on Micro-Structured Arrays.

Owing to its extremely low light absorption, black silicon has been widely investigated and reported in recent years, and simultaneously applied to various disciplines. Black silicon is, in general, fabricated on flat surfaces based on the silicon substrate. However, with three normal fabrication methods—plasma dry etching, metal-assisted wet etching, and femtosecond laser pulse etching—black silicon cannot perform easily due to its lowest absorption and thus some studies remained in the laboratory stage. This paper puts forward a novel secondary nanostructured black silicon, which uses the dry-wet hybrid fabrication method to achieve secondary nanostructures. In consideration of the influence of the structure’s size, this paper fabricated different sizes of secondary nanostructured black silicon and compared their absorptions with each other. A total of 0.5% reflectance and 98% absorption efficiency of the pit sample were achieved with a diameter of 117.1 μm and a depth of 72.6 μm. In addition, the variation tendency of the absorption efficiency is not solely monotone increasing or monotone decreasing, but firstly increasing and then decreasing. By using a statistical image processing method, nanostructures with diameters between 20 and 30 nm are the majority and nanostructures with a diameter between 10 and 40 nm account for 81% of the diameters.

A versatile approach to synthesise optically active hierarchical ZnS/ZnO heterostructures

One-dimensional hierarchical ZnS/ZnO heterostructures have been successfully fabricated by combining thermal evaporation method and in-situ/post oxidation process. Various morphologies of the secondary ZnO nanostructures such as nanosheets, nanoparticles, and nanoteeths were found to form on the ZnS nanowire backbone. The optical properties of the heterostructures were investigated by high-spatial resolution cathodoluminescence spectroscopy. It was demonstrated that optically active hierarchical ZnS/ZnO heterostructures, which strongly emit UV light with two emission bands at around 335 nm and 380 nm characterising both the ZnS and the ZnO phases, can be realised by controlling the oxidation temperature and duration. This research introduces a simple route to synthesise optically active ZnS/ZnO heterostructures.