Search

Ag3PO4–SnSe2 heterostructures are constructed as a sensing material and show excellent NO2-sensing performance at high relative humidity.

Bi2S3/ZnS heterostructures with increased surface-adsorbed oxygen and charge transfer in the dark were designed and used to achieve ppb level H2S detection at room temperature.

The Bi2S3/SnS2 heterostructure was synthesized and used as a bifunctional gas-sensing material through visible light modulation; it is ultrasensitive to NO2 under light irradiation but is highly selective to H2S in the dark.

Heterostructure construction is an effective strategy for enhancing the properties of functional materials.

Tin disulfide (SnS2) has been extensively researched as a promising sensing material due to its large electronegativity, suitable band gap, earth abundance, and nontoxicity. However, the poor conductivity and slow response/recovery speed at room temperature greatly hinder its application in high-performance practical gas sensors. Herein, to promote the study of SnS2-based gas sensors, a hierarchical SnS2/TiO2 heterostructure was synthesized and used as a sensing material to detect NO2 with the help of light illumination. Through the synergistic effect of the SnS2/TiO2 heterostructure and 525 nm light activation, the NO2 sensor based on the SnS2/TiO2 heterostructure exhibited a high response factor of 526% toward 1 ppm NO2 and a short response/recovery time of 43/102 s at room temperature due to the enhanced charge transfer and increased adsorption sites, which was superior to the vast majority of other NO2 sensors. An obvious decrease in the surface-adsorbed oxygen content based on the X-ray photoelectron spectroscopy measurement further confirmed that light illumination was helpful to clear the surface of SnS2/TiO2 and thus increased active sites for NO2 sensing. In addition, a flexible SnS2/TiO2 sensor was also fabricated to confirm its potential application in portable and wearable devices.

Layered tin diselenide (SnSe2) has aroused widespread scientific interest by virtue of its exceptional chemical, physical, and electrical characteristics. The distinctive features of SnSe2 enable it to be an ideal candidate for efficient detection of NO2 at room temperature. Herein, hierarchical SnSe2 assembled from thin nanosheets was designed and prepared through a facile solvothermal method. An ultralow detection limit (10 ppb) and considerable NO2 sensing performance were obtained at room temperature. A sensor based on hierarchical SnSe2 demonstrated a high response value of 1200% (triple that of SnSe2 nanosheets) and short response/recovery time of 50/55 s toward 10 ppm NO2. These remarkable sensing properties are uncommon in two-dimensional (2D) materials at room temperature. Additionally, the sensor exhibited superb selectivity, reliable reproducibility, and excellent long-term stability within 5 months. These enhanced sensing properties could be ascribed to the unique hierarchical structures, which possess large accessible space that enhances the adsorption and diffusion of gas molecules. This study offers a new strategy to improve the sensing performance of SnSe2 through rational morphology and structure design.

Constructing heterostructures could endow materials with exceptional properties in gas sensing applications owing to boosted interfacial charge transfer. The rational design and controllable synthesis of heterostructures with a high-quality interface, however, still remains a challenge. Herein, novel Sn atom cosharing SnO2/SnSe2 heterostructures with an intimate-contact interface and tunable composition were fabricated via a facile in situ oxidation method. An efficient increase in charge transfer can be achieved at the heterointerface through density functional theory calculations. The gas sensor based on SnO2/SnSe2 exhibited an ultrahigh response toward 10 ppm H2S at room temperature (resistance ratio = 32), roughly 4.5 and 16 times higher than that of pure SnO2 and SnSe2, respectively. Moreover, the sensor exhibited an ultralow detection limit of 10 ppb, superior sensing selectivity, and reliable long-term stability. This enhancement is primarily attributed to the numerous n–n heterojunctions, the boosted interfacial charge transfer, and the increased active sites of SnO2/SnSe2 heterostructures. The obtained results prove that SnO2/SnSe2 is a promising candidate material for room-temperature H2S gas sensing and offer guidance for rational material design to develop heterostructure-based sensors.

The two-dimensional layered metal dichalcogenides (LMDs) SnS2 is an interesting candidate for high-performance NO2 gas sensors. However, most SnS2-based NO2 sensors are usually inert for detecting ppb-level NO2 at room temperature (RT) because of the intrinsic features of a large bandgap, poor conductivity, and lack of active sites. Herein, we successfully endowed SnS2 with ppb-level NO2 detection at RT by using a carbon (C)-doping strategy. Compared to the pristine SnS2 showing a negligible response toward NO2 at RT, the C-doped SnS2 exhibited an excellent response (481.3% for 1 ppm and 146.5% for 100 ppb) with full recovery. The sensitivity toward ppb-level NO2 was as high as 1200% ppm−1. Moreover, the experimental and theoretical limit of detection (LOD) were down to 10 ppb and 0.3 ppb, respectively. Such impressive gas-sensing performance of C-doped SnS2 at RT was due to the doping-mediated synergistic effect of energy-band modification and the presence of an S vacancy. The results provide a real solution for developing high-performance LMDs-based gas sensors.

The sensing mechanism of luminescent metal-organic framework [Zn(3-tzba)(2,2′-bipy)(H2O)] -3H2O for formaldehyde detection was explored by using density functional theory and time-dependent density functional theory methods. Our investigation found that luminescent metal-organic framework [Zn(3-tzba)(2,2′-bipy)(H2O)] • 3H2O is able to interact with formaldehyde through hydrogen bonding to the framework. The luminescent mechanism of the hydrogen-bonded complex is photo-induced electron transfer; while the luminescent mechanism of luminescent metal-organic framework [Zn(3-tzba)(2,2′-bipy)(H2O)]-3H2O is ligand-to-ligand charge transfer. The intermolecu-lar hydrogen bond was found to be stronger in the excited state than that in the ground state by analyzing the geometry nuclear magnetic resonance, binding energy and infrared spectrum in different electronic states. Calculated fluorescence radiative rate coefficient and internal conversion rate coefficient qualitatively indicated a reduced radiative process and an enhanced internal conversion process of the hydrogen-bonded complex. The hydrogen-bonded complex exhibits luminescence weakening or even quenching due to the enhancement of the intermolecular hydrogen bond in the excited state compare with luminescent metal-organic framework [Zn(3-tzba)(2,2′-bipy)(H2O)]-3H2O. The variable luminescence demonstrated the potential of luminescent metal-organic framework [Zn(3-tzba)(2,2′-bipy)(H2O)]-3H2O as luminescent sensor for formaldehyde detection.

The effective detection of hazardous gases has become extremely necessary for the ecological environment and public health. Interfacial engineering plays an indispensable role in the development of innovative materials with exceptional properties, thus triggering a new revolution in the realization of high-performance gas sensing. Herein, the rational designed Ag

Tin disulfide (SnS

Promoting charge migration and enhancing redox ability of photogenerated carriers are important for the development of highly efficient semiconductor-based photocatalyst. Here, BiOBr/Bi

Defect and interlayer engineering are considered as two promising strategies to alter the electronic structures of sensing materials for improved gas sensing properties. Herein, ethylene glycol intercalated Al-doped SnS

Ever-increasing concerns over air quality and the newly emerged internet of things (IoT) for future environmental monitoring are stimulating the development of ultrasensitive room-temperature gas sensors, especially for nitrogen dioxide (NO

A core-shell structured dual Z-scheme ternary photocatalyst BiVO

Heterojunction engineering plays an indispensable role in improving gas-sensing performance. However, rational heterojunction engineering to achieve room-temperature NO

Efficiently harvesting solar energy for photocatalysis remains a challenge because near infrared (NIR) light with low excitation energy cannot be directly utilized by general semiconductor photocatalysts, although it makes up 46% of the solar spectrum. Herein, a broad-spectrum photocatalyst with pollutant adsorption-enrichment capability to enable natural sunlight-driven photocatalysis was synthesized by decorating a small amount of silver orthophosphate (Ag3PO4) nanodots on mesoporous silica (mSiO2)-functionalized upconversion nanoparticles (UCNPs; NaYF4:Yb,Tm@NaLuF4). The UCNPs play the role of broadening the absorption spectrum by upconverting NIR light into visible light, which can be absorbed by the Ag3PO4 nanodots. The functionalized hydrophilic mSiO2 shell not only facilitates the decoration of Ag3PO4 nanodots but is also capable of adsorbing and enriching pollutants around the Ag3PO4 nanodots to enhance the photocatalytic activity. Upon natural sunlight irradiation, the as-prepared photocatalyst (UCNP@mSiO2-Ag3PO4) exhibited remarkable photocatalytic activity with degradation rate constants of 0.24 and 0.051 min−1 under stirring and static conditions, exceeding that of the pure Ag3PO4 sample by factors of 4.2 and 12.5, respectively. Thus, it can be anticipated that the design of photocatalysts with the synergy of broadband absorption and pollutant adsorption-enrichment will be a promising strategy to realize efficient sunlight-driven photocatalysis, even without extra mechanical stirring for future scaled-up water treatment.

Two twisted π-conjugated cruciform luminophores DMTCS-CC6 and DBTCS-CC6 characterized by rigid X-shaped geometry with two conjugated donor and acceptor intersecting at the central aromatic core have been rationally designed and successfully synthesized. Spectral analysis and theoretical calculations studies indicated that the two cross-conjugated compounds showed unique intramolecular charge-transfer (ICT) process from the donor (carbazole) to the acceptor (dicyanodistyrylbenzene) axis in the excited state. Especially, DMTCS-CC6 and DBTCS-CC6 exhibited efficient aggregation-induced emission (AIE) and high contrast mechanofluorochromic (MFC) properties. By simple grinding, the as-prepared powders of DMTCS-CC6 and DBTCS-CC6 emitting strong yellowish-green (540 nm) and yellow light (560 nm) under UV irradiation could be transferred into powders emitting yellow (582 nm) and red (609 nm), respectively, the red shifts of 42 and 49 nm were observed. Such mechanochromism was reversible upon the treatment of grinding and fuming with DCM. The XRD patterns suggested that the MFC behavior originated from the transition between the crystalline and amorphous states. More interestingly, DBTCS-CC6 exhibited more obvious AIE and more contrast MFC behavior relative to DMTCS-CC6. This is a result of the quite larger space hindrance induced by 3,5-bis(trifluoromethyl)phenyl with two trifluoromethyl groups bonded at meta positions could make DMTCS-CC6 exhibit more twisted spatial conformation, leading more efficient solid state fluorescence and better structural transformability.

The slow response and incomplete recovery are primary bottlenecks for the sensing performance of 2D transition-metal dichalcogenides (TMDs) at room temperature, which hinders their development for state-of-the-art gas sensors. Herein, we engineered N doped p-type MoS2 against its native n-type propensity to enable a rapid room-temperature response/recovery detection of NO2. Compared to pristine n-type MoS2 showing typical slow response and no recovery (1544 s/-), the prepared N-doped MoS2 sensor exhibits a fast response/recovery (22/109 s) toward 10 ppm NO2 at room temperature. In addition, the N dopants endow MoS2 with a sensing response of 28% to 10 ppm NO2, ppb-level of detection limit (125 ppb), excellent selectivity, good repeatability, and humidity resistance. We underline the fast response/recovery mechanism of N-doped MoS2 to be the N dopants triggered synergistic effect of new active sites and fast charge transfer based on density functional theory calculation and Hall-Effect measurement. We hope this result may shed a new light on the development of TMDs-based sensing materials aiming at improving their room-temperature response/recovery performance.

Defect and interlayer engineering are considered as two promising strategies to alter the electronic structures of sensing materials for improved gas sensing properties. Herein, ethylene glycol intercalated Al-doped SnS2 (EG-Al–SnS2) featuring Al doping, sulfur (S) vacancies, and an expanded interlayer spacing was prepared and developed as an active NO2 sensing material. Compared to the pristine SnS2 with failure in detecting NO2 at room temperature, the developed EG-Al–SnS2 exhibited a better conductivity, which was beneficial for realizing the room-temperature NO2 sensing. As a result, a high sensing response of 410% toward 2 ppm NO2 was achieved at room temperature by using the 3% EG-Al–SnS2 as the sensing material. Such outstanding sensing performance was attributed to the enhanced electronic interaction of NO2 on the surface of SnS2 induced by the synergistic effect of Al doping, S vacancies, and the expanded interlayer spacing, which is directly revealed by the in-suit measurement based on near-ambient pressure X-ray photoelectronic spectroscopy (NAP–XPS). Furthermore, to identify the role of Al doping, S vacancies, and the expanded interlayer spacing in enhancing the NO2 sensing properties, a series of comparative experiments and theoretical calculations were performed.

Advanced semiconductor heterostructures based on 2D materials present fascinating chemical, electronic, and geometric effects on chemical sensing and hold a great promise for developing high-performance gas sensors. However, the conventional tandem heterostructures may suffer from severe defect scattering as well as inferior heterointerface, thus limiting their sensing performance as the result of hindered interfacial charge transfer. Herein, we present a hierarchical assembly of SnO2-rGO/SnS2 heterostructure with 2D reduced graphene oxide (rGO) acting as a transfer highway to bridge n-type SnO2 nanowires and n-type SnS2 nanoflakes, resulting in novel ternary n-g-n junctions for the improvement of charge transport efficiency and thus enabling ultra-sensitive NO2 gas detection. Compared to pure SnO2/SnS2 and SnS2 sensors, the sensing response of n-g-n junctioned SnO2-rGO/SnS2 sensor reaches 1064 toward 10 ppm NO2, exceeding the corresponding sensors by a factor of 18 and 35, respectively. The SnO2-rGO/SnS2 sensor also exhibits an extremely low detection limit down to 10 ppb, short response and recovery times (42 and 111 s, respectively), excellent selectivity, long-term stability, and humidity resistance. We believe such a ternary architectural design with the novel n-g-n heterojunction engineering would provide a new approach towards future ultrahigh-performance gas sensing.

SnS2 nanosheets with unique properties are excellent candidate materials for fabricating high-performance NO2 gas sensors. However, serious restacking and aggregation during sensor fabrication have greatly impacted the sensing response. In this study, flower-like hierarchical SnS2 was prepared by a simple microwave method and partially thermally oxidized to form hierarchical SnS2/SnO2 nanocomposites to further improve the sensing performance at low operating temperature. The fabricated SnS2/SnO2 sensor exhibited ultrahigh response (resistance ratio = 51.1) toward 1 ppm NO2 at 100 °C, roughly 10.2 times higher than that of pure SnS2 nanoflowers. The excellent and enhanced NO2 sensing performances of hierarchical SnS2/SnO2 nanocomposites were attributed to the novel hierarchical structure of SnS2 and the nanoheterojunction between SnS2 and the ultrafine SnO2 nanoparticles. The SnS2/SnO2 sensors also exhibited excellent selectivity and reliable repeatability. The simple fabrication of high performance sensing materials may facilitate the large-scale production of NO2 gas sensors.

Metal oxide/graphene nanocomposites are emerging as promising materials for developing room-temperature gas sensors. However, the unsatisfactory performances owing to the relatively low sensitivity, slow response, and recovery kinetics limit their applications. Herein, a highly sensitive and rapidly responding room-temperature NO2 gas sensor based on WO3 nanorods/sulfonated reduced graphene oxide (S-rGO) was prepared via a simple and cost-effective hydrothermal method. The optimal sensor response of the WO3/S-rGO sensor toward 20 ppm NO2 is 149% in 6 s, which is 4.7 times higher and 100 times faster than that of the corresponding WO3/rGO sensors. In addition, the sensor exhibits excellent reproducibility, selectivity, and extremely fast recovery kinetics. The mechanism of the WO3/S-rGO nanocomposite gas sensor is investigated in detail. In addition to the high transport capability of S-rGO as well as its excellent NO2 adsorption ability, the superior sensing performance of the S-rGO/WO3 sensor can be attributed to the favorable charge transfer occurring at the S-rGO/WO3 interfaces. We believe that the strategy of compositing a metal oxide with functionalized graphene provides a new insight for the future development of room-temperature gas sensors.

The unique features of SnS

A theoretical investigation of hydroxide ion transport mechanism in quaternary ammonium functionalized polystyrene (QAPS) anion exchange membrane (AEM) was studied by density functional theory (DFT). The results showed that there were two steps for OH− transferring through QAPS-AEM. The first step was the movement of OH− in water channel, which was induced by frequently forming and breaking of hydrogen bonds (H-bonds) between H2O and OH−. The second step was that OH− transferred across the quaternary ammonium (QA) groups by following the rotation about C C single bond, which was the rate-determining step for OH− transferring in QAPS-AEM. We presented that the ionic groups on the side chain of polymer with smaller space steric should provide higher ion conductivity due to their lower rotation energy barriers.

Ever-increasing concerns over air quality and the newly emerged internet of things (IoT) for future environmental monitoring are stimulating the development of ultrasensitive room-temperature gas sensors, especially for nitrogen dioxide (NO2), one of the most harmful air pollution species released round-the-clock from power plants and vehicle exhausts. Herein, tin dioxide nanorods/ethylenediamine-modified reduced graphene oxide (SnO2/EDA-rGO) heterojunctions with selective adsorption and electronic structure modulation were engineered for highly sensitive and selective detection of NO2 at room temperature. The modified EDA groups not only enable selective adsorption to significantly enrich NO2 molecules around the interface but also realize a favorable modulation of SnO2/EDA-rGO electronic structure by increasing the Fermi level of rGO, through which the sensing performance of NO2 is synergistically enhanced. The response of the SnO2/EDA-rGO sensor toward 1 ppm NO2 reaches 282%, which exceeds the corresponding SnO2/rGO sensor by a factor of 2.8. It also exhibits a low detection limit down to 100 ppb, enhanced selectivity, and rapid response/recovery kinetics. This approach to designing a novel heterojunction with significantly enhanced chemical and electric effects may shed light on the future engineering of gas-sensing materials.

The rapid recombination and poor redox capability of photoinduced charge carriers seriously impede the photocatalytic activity. Herein, a direct Z-scheme photocatalyst was fabricated by selectively depositing Ag6Si2O7 nanoparticles (NPs) on the {0 4 0} facets of BiVO4. Owing to the facet-dependent band structure of BiVO4, the photoinduced electrons and holes can be pre-separated upon photoillumination and transfer to {0 4 0} and {1 1 0} facets of BiVO4, respectively. A rapid combination of the separated electrons at the {0 4 0} facets of BiVO4 with holes of the Ag6Si2O7 NPs then takes place triggering a direct Z-scheme photocatalysis. Such a charge pre-separation triggered by the faceted BiVO4, together with Z-scheme at the interface warrants not only effective photoinduced charge separation but also excellent redox capability owing to the increased redox potential. The photocatalytic rate constant of the optimum BiVO4{0 4 0}/Ag6Si2O7 heterostructure is 28.2 and 17.2 times higher than those of pristine BiVO4 and Ag6Si2O7, respectively. This study offers a new insight for constructing direct Z-scheme photocatalysts with high degradation efficiency based on facet-controlled crystals.

SnS2 nanosheets with unique properties are excellent candidate materials for fabricating high-performance NO2 gas sensors. However, serious restacking and aggregation during sensor fabrication have greatly impacted the sensing response. In this study, flower-like hierarchical SnS2 was prepared by a simple microwave method and partially thermally oxidized to form hierarchical SnS2/SnO2 nanocomposites to further improve the sensing performance at low operating temperature. The fabricated SnS2/SnO2 sensor exhibited ultrahigh response (resistance ratio = 51.1) toward 1 ppm NO2 at 100 °C, roughly 10.2 times higher than that of pure SnS2 nanoflowers. The excellent and enhanced NO2 sensing performances of hierarchical SnS2/SnO2 nanocomposites were attributed to the novel hierarchical structure of SnS2 and the nanoheterojunction between SnS2 and the ultrafine SnO2 nanoparticles. The SnS2/SnO2 sensors also exhibited excellent selectivity and reliable repeatability. The simple fabrication of high performance sensing materials may facilitate the large-scale production of NO2 gas sensors.

Environmental problems due to the discharge of gases, including NO and CO2, in addition, diseases caused by improper concentration of NO and CO2 in vivo must be resolved. In this study, Grand canonical Monte Carlo (GCMC) simulations are combined with density functional theory (DFT) to calculate the adsorption of NO and CO2 from a dual-component mixture to the Cu-BTC metal organic framework. The results show that the adsorption isotherms for various molar ratios of the gaseous mixture followed a Langmuir distribution. At higher pressures more CO2 than NO was adsorbed by Cu-BTC, with NO showing a tendency to desorb. However, better results for adsorption of NO were observed at lower pressures. For the different pressure and molar ratios of the gaseous mixture examined, more CO2 than NO was always adsorbed. Compared with three-way catalysts, Cu-BTC offers benefits to adsorption of CO2 and NO from gaseous mixtures without increased durability problems.

Density functional theory and time-dependent density functional theory methods have been used to investigate the hydrogen bonding between the Metal–organic framework [Zn2(H2L)(2,2′-bpy)2(H2O)]n and formaldehyde in the electronically excited state. The calculated geometric configuration, 1H NMR chemical shift and IR spectra of the hydrogen-bonded complex demonstrated that the hydrogen bond was strengthened in the excited state S1. The strengthening of the hydrogen bond in the S1 state would lead to a luminescence decreasing phenomenon of [Zn2(H2L)(2,2′-bpy)2(H2O)]n, and the fluorescent rate constant of [Zn2(H2L)(2,2′-bpy)2(H2O)]n was decreased when encapsulating formaldehyde into it. Taken together, these results indicated that [Zn2(H2L)(2,2′-bpy)2(H2O)]n could be used for the detection of formaldehyde.

Relativistic density functional theory (DFT) computations were performed to investigate the dynamic motion of an encapsulated Lu pair inside a C76(Td) cage. The results revealed that the lowest-energy configuration of Lu2@C76(Td) adopts C2 symmetry; four electrons are transferred to the outer carbon cage and the two encapsulated Lu atoms form a metal–metal single bond (with an electronic structure of Lu24+@C764−), and the good electron delocalization in the C764−(Td) cage partially contributes the thermodynamic preference of Lu2@C76(Td). The rather small barrier (3.2 kcal mol−1) for Lu2 atoms to hop from one stable site to another leads to flexible motion of the Lu pair inside the parent fullerene cage, and the Oh symmetrical motion trajectory of two Lu atoms is consistent with the STM image. The computed 13C NMR spectrum with this trajectory also agrees well with the experimental results.

With the aids of density functional theory (DFT) and time-dependent density functional theory (TD-DFT), the explosives-detection mechanism of a typical luminescent metal–organic framework (MOF) sensor has been comprehensively studied by investigating the interactions between the framework and two analytes, namelty, benzene and nitrobenzene. By studying both the periodic crystal models and cluster models we obtained an in-depth understanding of the detecting mechanism from the viewpoint of electronic coupling between the analyte and sensor. Intermolecular electron transfer from the conduction bands of the framework to the LUMO of nitrobenzene is demonstrated to induce the luminescence quenching phenomenon observed in previous experiments. π–π stacking and hydrogen bonding interactions are found to play essential roles in this intermolecular electron transfer process. π–π stacking provides large fragment orbital overlaps between the unoccupied orbitals of the analyte and sensor, which serves as a highly efficient electron transfer bridge. Hydrogen bonds alone cannot provide enough overlaps for electron transfer but are found to reinforce the π–π stacking interactions. The cooperation of the two interactions induces facile intermolecular electron transfer which strongly quenches the luminescence of the MOF sensor. This work sheds light on the analyte–sensor interactions inside the MOF sensors and would provide valuable insights into the design of high efficient explosives-detecting MOF sensors.

The influence of CH 3 OH solvent on the luminescent properties of the [Zn(sfdb)(bpy)(H 2 O)] n · 0.5 n CH 3 OH (sfdb = 4,4-sulfonyldibenzoic acid, bpy = 2,2-bipyridine) metal–organic framework (MOF) was investigated by considering the hydrogen bond between CH 3 OH and [Zn(sfdb)(bpy)(H 2 O)] n in an electronically excited state using density functional theory and time-dependent density functional theory methods. The calculated geometry, infrared spectrum, and UV–vis spectrum in the ground state are consistent with the experimental results. The frontier molecular orbitals and electronic configuration indicated that the origin of the luminescence is ligand-to-ligand charge transfer rather than ligand-to-metal charge transfer, as has been previously proposed. We found that the O3⋯H11 hydrogen bond is weaker in the excited state than in the ground state, and the weaker hydrogen bond in the electronically excited state should enhance the luminescence. The results show that the CH 3 OH solvent changes the luminescence properties of [Zn(sfdb)(bpy)(H 2 O)] n , which provides potential opportunities for the design of diverse luminescent MOFs.

The site-selective deposition of organic molecules onto template structures to create ordered micro/nanoscale arrangements has drawn more and more attention because of the broad possibility, for example, application in organic electronic devices. Here we present a molecular dynamics study toward the selective deposition of organic molecules 3(5)-(9-anthryl) pyrazole (ANP), perylene and sexiphenyl (6P) onto template structures made of the phospholipid L-α-dipalmitoyl-phosphatidylcholine (DPPC) in alternating liquid expanded (LE) and liquid condensed (LC) states. The simulation results indicate, first of all, that the molecules immerge into both LE and LC phases instead of staying on top of them. Furthermore, the simulations replicate the empirically observed higher diffusion constants of the organic molecules on LE phase compared to LC phase of the underlying DPPC layer. Additionally, we propose a possible mechanism for the diffusion barrier between LE/LC phase needed to explain the experimental findings of the selective deposition. Altogether, this study supports the notions suggested by the experiments on the causes of the selective deposition while giving a deeper insight into the molecular processes involved.

We report a simple and low-cost nonlithographic approach to fabricate tapered silicon arrays for broad-band antireflective coatings. Wafer-scale, subwavelength-structured pyramidal arrays are directly patterned on Si using mixed self-assembled monolayers consisting of octadecyltrichlorosilane islands as KOH etching masks. We have investigated the effects of etching conditions (such as temperature and pH of solution and etching time) on antireflective properties. The reflectivity of Si surfaces can be suppressed to below 3.8% in the waveband of 300−2000 nm. This technique combines the simplicity of self-assembly and cost benefits of chemical etching, which is promising for reducing the manufacturing cost of crystalline silicon solar cells and optical devices.

We report a simple bottom-up approach for the fabrication of highly antireflective optical surfaces. The Langmuir−Blodgett (LB) monolayer with domain structures was used as a mask for selective etching of Si in a KOH solution. The obtained pyramidal structures can reduce the reflectivity to less than 6% at the wavelengths from 400 to 2400 nm. This technique combines the simplicity and scalability of self-assembly and cost benefits of chemical etching. These antireflective structures may have potential applications in optical devices and solar cells. Moreover, the reflectivity of polymer materials can also be reduced by transferring the pyramidal structures onto their surfaces via molding and nanoimprint lithography (NIL).

Graphene and its derivatives are attractive for electrocatalytical application in dye-sensitized solar cells because of their unique structures and electronic properties. By means of density functional theory calculations, the mechanism of triiodide reduction reaction on nitrogen-doped graphene (NDG) was studied in acetonitrile environment. The computations demonstrated that the rate-determining step was the ability of NDG to release electrons to active iodine atoms. According to the calculation, the optimal NDG was designed with nitrogen contents of 4.0 % graphite N and 3.0 % pyridinic N approximately. In order to precisely distinguish these two nitrogen species in the optimal NDG, we proposed the chemical shift of 15N NMR of nitrogen doped in graphene provided guidance for the experiments.

In these cases, a multistep processfor fabrication is unavoidable, which limits the spatial resolu-tion and increases fabrication costs. Here we demonstrate amethod for realizing patterned surfaces with different emis-sion colors by using a one-step gas-phase strategy that depos-its a single molecular species on a prepatterned solid substrateby nanoimprint lithography. This approach relies on the spec-tral shift of dye molecules in different aggregation states,which is a well-known behavior in solutions but not as com-mon on solid supports.

Carbon quantum dots (CQDs) had attracted much attention due to their unique structures and excellent properties. Their green preparation was one of the research frontiers. However, most of the CQDs were prepared by strong acid oxidation, the way of which was not friendly to the environment. In this study, CQDs were prepared by green ozone oxidation of lignite coal, which is abundant and inexpensive. The CQDs were well dispersed, the size distribution of the obtained CQDs centralized from 2 to 4 nm with the average diameter of about 2.8 nm. In addition, the as-prepared CQDs containing rich oxygen functional groups exhibited good water-solubility and optical properties with yield reached 35%. The CQDs showed a highly sensitive and selective quenching effect to Fe3+ with desirable anti-interference performance. Moreover, the fluorescence intensity of CQDs had a good linear response to the Fe3+ concentration ranging from 10 to 150 µmol/L with the detection limit of 0.26 µmol/L. This green and facile synthesis method had the prospect of large-scale preparation of CQDs.

In this work, we report an approach to fabricate Si nanopillar arrays by nanosphere lithography. With this method, the periods of Si arrays can be controlled by using different sized spheres. The produced Si arrays exhibit broadband antireflections, and the spectral positions with low reflection strongly depend on the periods of the arrays. Thus, the wavelength range of low reflection can be tuned by varying the period of Si array.

An efficient fabrication technique for large area periodic metallic split-ring arrays has been demonstrated by the combination of tilted nanoimprint lithography and nanotransfer imprinting. The feature size of the split-rings can be adjusted by varying the key geometry parameters of the original imprinting mold. Due to the flexible nature of PDMS molds, these arrays can be patterned on curved surfaces. The molds for nanoimprint lithography and nanotransfer imprinting can be used multiple times without a loss of fidelity.