Guest Type Research Articles

Experimental and Theoretical Insights on Gas Trapping of Noble Gases in MFU-4-Type Metal-Organic Frameworks.

Isostructural metal-organic frameworks (MOFs), namely MFU-4 and MFU-4-Br, in which the pore apertures are defined by anionic side ligands (Cl- and Br-, respectively), were synthesized and loaded with noble gases. By selecting the type of side ligand, one can fine-tune the pore aperture size, allowing for precise regulation of the entry and release of gas guests. In this study, we conducted experiments to examine gas loading and release using krypton and xenon as model gases, and we complemented our findings with computational modeling. Remarkably, the loaded gas guests remained trapped inside the pores even after being exposed to air under ambient conditions for extended periods, in some cases for up to several weeks. Therefore, we focused on determining the energy barrier preventing gas release using both theoretical and experimental methods. The results were compared in relation to the types of hosts and guests, providing valuable insights into the gas trapping process in MOFs, as well as programmed gas release in air under ambient conditions. Furthermore, the crystal structure of MFU-4-Br was elucidated using the three-dimensional electron diffraction (3DED) technique, and the bulk purity of the sample was subsequently verified through Rietveld refinement.

Terbium-benzoyl acetate complex encored indium-MOFs through post-synthetic modification for luminescent sensitive detection of organophosphorus insecticides

Metal-organic frameworks (MOFs) are represented ideal candidate materials for chemical sensing of different kinds of species because they contain optically active sites may be in organic linker or ions node, moreover, MOFs have high porosity that capture different types of guests. Lanthanide MOFs (Ln-MOFs) was very common in sensing chemical species due to identical light emission characteristics. The problem of Ln-MOFs was the difficulty of its preparation; therefore, post-synthetic modification (PSM) technique was excellent for incorporation of lanthanide site in the network. Unlike other MOFs, In-MOF can be post-synthesized because of its free amino group in the network, therefore, it was chosen in the current work. Here, Tb-In-MOF-EBA was generated by PSM of In-MOF in two steps: (1) formation of the amide by the reaction of In-MOF with ethyl benzoyl acetate; (2) chelation of Tb3+ cations by the diketone fragment. The main challenge of present work is not to give another luminescent MOF based sensor rather than using decorative technique based PSM route to tune optically active sensors for organophosphorus (OP) insecticides (dimethoate, chlorpyrifos, and pirimiphos-methyl) identification quantitatively and qualitatively. The emission intensity of Tb-In-MOF-EBA were reduced with 8 %, 50 %, and 81 %, after adding dimethoate, chlorpyrifos, and pirimiphos-methyl for the parent compounds, respectively. Tb-In-MOF-EBA showed interesting selectivity toward dimethoate, chlorpyrifos, pirimiphos-methyl, therefore, it can be used in measuring the concentration of OP insecticide with high accuracy.

Empirical investigation of occupant-centric thermal comfort in hotel guestrooms

Given the importance of occupant satisfaction with thermal comfort in hotel accommodations, previous studies have assessed thermal comfort using either local or global standards. In a hotel catering to diverse guests, a single standard may constrain the formulation of an optimal strategy for improving occupant satisfaction. To address this challenge, this study empirically investigates occupant-centric thermal comfort in hotel guestrooms located in a hot and humid climatic region. To this end, a living-lab-based case study was conducted on a hotel guestroom in Hong Kong, wherein two types of thermal comfort improvement strategies were devised from both local and global perspectives. First, to improve thermal comfort in line with the local standard, it was determined that an ancillary fan coil unit (FCU) energy consumption of 6.0 kW h (approximately 34 % of the existing energy consumption) was required. Second, to improve thermal comfort in line with the global standard, an ancillary FCU energy consumption of 9.4 kW h (approximately 53 % of the existing energy consumption) was necessary. Consequently, in a hot and humid climatic region, the distribution of thermal comfort may vary depending on the type of guest (e.g., domestic or foreign), and ancillary cooling energy expenditure may be incurred to enhance a guest's thermal comfort. The proposed approach is expected to contribute to the creation of occupant-tailored thermal comfort by considering an individual's thermal acclimation to a specific climatic region from both local and global perspectives.

Inventories, Interiors, and Women’s Ambitions: Strategies of Property Ownership in Three Mid-19th Century Montreal Public Houses

Notarized inventories provide an important window onto the interiors of public houses, the image that keepers sought to project of their businesses and of themselves, and the type of guests they wanted to attract. In this micro history, I examine the degree of differentiation amongst three widows operating modest businesses located in highly trafficked Montreal neighbourhoods, in particular, the composition of their domestic capital, the business strategies they employed, and if they achieved social mobility. We know from earlier studies that movables were significant assets for earning a living, often critical to the survival of a widowed, separated, or abandoned woman. My argument goes further. I contend that women attempted, and some were able, to convert movables into immovable property, assets that were more secure and versatile. While publicans displayed a wide array of skills, statuses, and achievements, these three cases focus on the critical threshold, that interesting set of people at the boundary, aware of and struggling to achieve property ownership.

Nucleation Curves of Carbon Dioxide Hydrate in the Absence of a Solid Wall

Nucleation kinetics of clathrate hydrate is poorly understood because of the difficulties in determining the essential parameter, nucleation rate. Nucleation rate enables quantitative comparisons of the impacts of various additives and solid walls on nucleation. We made a setup that determines the nucleation curves of structure I─forming CO2 hydrate in quiescent quasi-free water droplets supported by a bulk of liquid perfluoromethyldecalin under isobaric conditions. The results were compared to the nucleation rates of CO2 hydrate in quiescent water that was in direct contact with stainless-steel walls. We assessed the convergence of the nucleation curves with the increasing numbers of nucleation data and compared our results to the nucleation rates of methane/propane mixed gas hydrate in quiescent quasi-free water droplets and the nucleation rates of gas hydrates of various guest types in the presence of solid walls reported in the literature. We found that (1) 400 nucleation events were sufficient to construct a reliable nucleation curve; (2) the addition of stainless-steel walls promoted the nucleation kinetics of CO2 hydrate, as it did to methane/propane mixed gas hydrate; (3) the kinetic parameter was significantly lower than the theoretically expected value, whereas the thermodynamic parameter was comparable to both the theoretically expected value and the experimentally determined value reported in the literature; and (4) CO2 hydrate nucleated over a substantially shallower supercooling range and had higher nucleation rates than those of methane/propane mixed gas hydrate, both in the presence and in the absence of a solid wall.

BOOKER PREDICTION FROM REQUESTS FOR QUOTATION VIA MACHINE LEARNING TECHNIQUES

Purpose – Many incoming requests for quotation usually compete for the attention of accommodation service provider staff on a daily basis, while some of them might deserve more priority than others. Design – This research is therefore based on the correspondence history of a large booking management system that examines the features of quotation requests from aspiring guests in order to learn and predict their actual booking behavior. Approach – In particular, we investigate the effectiveness of various machine learning techniques for predicting whether a request will turn into a booking by using features such as the length of stay, the number and type of guests, and their country of origin. Furthermore, a deeper analysis of the features involved is performed to quantify their impact on the prediction task. Findings – We based our experimental evaluation on a large dataset of correspondence data collected from 2014 to 2019 from a 4-star hotel in the South Tyrol region of Italy. Numerical experiments were conducted to compare the performance of different classification models against the dataset. The results show a potential business advantage in prioritizing requests for proposals based on our approach. Moreover, it becomes clear that it is necessary to solve the class imbalance problem and develop a proper understanding of the domain-specific features to achieve higher precision/recall for the booking class. The investigation on feature importance also exhibits a ranking of informative features, such as the duration of the stay, the number of days prior to the request, and the source/country of the request, for making accurate booking predictions. Originality of the research – To the best of our knowledge, this is one of the first attempts to apply and systematically harness machine learning techniques to request for quotation data in order to predict whether the request will end up in a booking.

Use of shear sensitive coloured guest component to track powder mixing in adhesive binary mixtures

The mixing performance in binary powder blends with components exhibiting guest and host type interactions was assessed by tracking the colour change of the mixture. . The operation parameters like mixing time and speed were studied in compositions containing lactose monohydrate as host and iron oxide nanoparticle as coloured guest components . The mixing characteristics were analysed through visual imaging and colorimetric estimations. Furthermore, surface analytical techniques like scanning electron microscope (SEM) for surface area coverage (SAC) determination and Finite Dilution Inverse Gas chromatography (FD-IGC) for surface energy heterogeneity characterisation were employed. The mixing sensitivity of the coloured tracer and the consequent colour transitions under different conditions helped in validating the mixing performance and operation conditions. The FD-IGC results showed lowering of the energetic heterogeneity for better quality mixtures. Thus, a shear sensitive coloured nano-tracer can be utilised for a simple, quick and cost-effective estimation of the mixture quality and for the validation of mixing process. • Binary powders with guest-host interactions studied. • Mixing performance was tracked using iron oxide guest. • Binary mixtures examined through colorimetric, FD-IGC and SEM analysis. • A simple, quick and cost-effective approach for mixing process validation reported.

Host-guest synergy of CH3NH3PbBr3@Ln-MOFs enabling tunable green luminescence and switchable memory

Metal organic frameworks (MOFs) contain ordered pores capable of encapsulating varied types of guests and provide a platform to expand the flexibility and versatility of the host-guest composites. Herein, by encapsulating CH3NH3PbBr3 NPS into Ln-MOFs (Ln = La, Nd, Pr, Sm), four CH3NH3PbBr3@Ln-MOFs host-guest composites were fabricated and served as a bifunctional platform. The temperature-dependent luminescence properties of the CH3NH3PbBr3@Ln-MOFs were explored and the results revealed their tuneable green luminescence performance. In particular, the CH3NH3PbBr3@Sm-MOF exhibits a variety of colours from green to blue to purple and an excellent quantum yield of 0.98. The photocurrent responses and theoretical calculations reveal the enhancement mechanism of CH3NH3PbBr3 on charge-hole separation owing to its unique host-guest synergy. Moreover, the CH3NH3PbBr3@Sm-MOF exhibits the excellent electrical bi-stability with a high ON/OFF ratio of 104. Hence, the CH3NH3PbBr3@Ln-MOFs host-guest composites are promising candidates for a new generation of photovoltaic, light-emitting, and switching memories devices.

Supramolecular assemblies of cucurbit[n]urils and 4-aminopyridine controlled by cucurbit[n]uril size (n = 5, 6, 7 and 8)

The binding interactions between 4-aminopyridine (4-AP) and a series of cucurbit[n]urils (Q[5], Q[6], TMeQ[6], Q[7], Q[8]) have been studied using 1H NMR spectroscopy, UV–vis absorption spectroscopy, isothermal titration calorimetry (ITC) and X-ray crystallography. The data indicates that the Q[5]@4-AP complex exhibits exo binding, which is not observed in the other four host-guest complexes. Furthermore, X-ray crystallography clearly reveals how the Q[n]s bind with 4-AP to form complexes, for example Q[5] forms an outer-surface complex, whilst Q[6], TMeQ[6] and Q[7] formed 1:1 host and guest type complexes, and Q[8] formed a stable 1:2 ternary complex due to its large cavity, which can accommodate two 4-AP molecules.

Tunable and Thermally Stable Luminescence from Polycyclic Aromatic Hydrocarbons Confined in a Zeolitic Imidazolate Framework

AbstractMetal–organic frameworks (MOFs) can provide a variety of nanocompartments for the confinement of guest molecules. Furthermore, the emissions of fluorescent molecules can be tuned by confinement. In this study, a solvent‐free “bottle‐around‐ship” method is used to encapsulate perylene and 9,10‐dimethylanthracene, two polycyclic aromatic hydrocarbons, in the MOF ZIF‐8. Luminescence color tuning is achieved, including white‐light emission, when controlling the loading of only a single type of guest. Photophysical analysis suggests that the variations in luminescence result from various guest arrangements in the nanocompartments, as well as host–guest interactions. Because of the tight confinement of the guests, this host–guest system displays excellent luminescence thermal stability.

A concise treatise on model-based enhancements of cohesive powder properties via dry particle coating

• Advances in model-guided dry coating of cohesive powder flow enhancement presented. • Chen-NJCEP model explains the mechanism of dry coating induced flow enhancements. • Models offered for the guest amount and type, and granular Bond number estimation. • Dry coating led to drastically enhance flow, packing, agglomeration, dissolution. • Agglomeration, indicator of flowability, dramatically reduced with dry coating. This paper presents a review of our key advances in model-guided dry coating-based enhancements of poor flow and packing of fine cohesive powders. The existing van der Waals force-based particle-contact models are reviewed to elucidate the main mechanism of flow enhancement through silica dry coating. Our multi-asperity model explains the effect of the amount of silica, insufficient flowability enhancements through conventional blending, and the predominant effect of particle surface roughness on cohesion reduction. Models are presented for the determination of the amount and type of guest particles, and estimation of the granular Bond number, used for cohesion nondimensionalization, based on particle size, particle density, asperity size, surface area coverage, and dispersive surface energy. Selection of the processing conditions for LabRAM, a benchmarking device, is presented followed by key examples of enhancements of flow, packing, agglomeration, and dissolution through the dry coating. Powder agglomeration is shown as a screening indicator of powder flowability. The mixing synergy is identified as a cause for enhanced blend flowability with a minor dry coated constituent at silica < 0.01%. The analysis and outcomes presented in this paper are intended to demonstrate the importance of dry coating as an essential tool for industry practitioners.

Innovating in the Tourism Industry Through Virtual Reality (VR) and Education in the Hotel Business

In the interdisciplinary co-operation of experts in the fields of technology, hospitality, and pedagogy, a 3D training module was created, which simulates the environment of a hotel reception. Key elements of communication between hotel staff and various types of guests were identified, and variant scenarios of communication situations were prepared. Scenarios are based on the principles of effective simulation. The methodology of training communication skills of hotel employees using virtual reality tools was compiled on the basis of foreign research in the field of using virtual reality in training processes. The tool is a pilot test in teaching tourism workers, specifically for the development of their communication skills in dealing with clients. The paper presents, in detail, a model of virtual reception and methodology of communication skills training, which was verified on students who are preparing to work in tourism, as well as on hotel staff with experience.

Molecular Dynamics Simulation Studies on the Stability and Dissociation of Clathrate Hydrates of Single and Double Greenhouse Gases

Comprehending and controlling the stability and dissociation of greenhouse gases hydrates are critical for a variety of hydrate-based industrial applications, such as greenhouse gas separation, sequestration, or utilization. Although the promotion effects of greenhouse F-gases (F-promoters) and new cyclic promoters on CO2 hydrates have been acknowledged, the involved molecular mechanisms are poorly understood. This work was therefore conducted to investigate the intermolecular mechanisms of the properties of CO2 and NF3 hydrates using molecular dynamics (MD) simulation to better understand their stability and dissociation and the effects of thermodynamic conditions as well as cage occupancy. In addition, the stability of CO2/CO2 + CH4 hydrates in the presence of seven thermodynamic hydrate promoters (THPs) from different molecular groups or substituents was evaluated. Results reveal that after the breakup of the hydrate, the propensity of NF3 to form nanobubbles is more than that of CO2 molecules. The relative concentration distribution of partially occupied hydrates was also found to be greater than that of completely filled by guest gases. MD simulation results of CO2 double and mixed hydrates also show that the type of large molecular guests in the large cages plays a major role in the stabilization of the clathrate hydrate network. The structural properties, however, indicate that the resistance against being dissociated for CO2 + promoter can be somewhat increased when half of the CO2 molecules in small cages is replaced by CH4. In addition, the existence of neopentyl alcohol in large cavities was found to facilitate the process of hydrate dissociation by making new hydrogen bonds between hydroxyl groups and water molecules. Among studied systems with THPs, cyclopentane, and cyclohexane in comparison with F-promoters seem to be more susceptible to maintaining the stability of CO2 clathrate hydrate.

Ternary host-guest complexes with rapid exchange kinetics and photoswitchable fluorescence

SummaryConfinement within molecular cages can dramatically modify the physicochemical properties of the encapsulated guest molecules, but such host-guest complexes have mainly been studied in a static context. Combining confinement effects with fast guest exchange kinetics could pave the way toward stimuli-responsive supramolecular systems—and ultimately materials—whose desired properties could be tailored “on demand” rapidly and reversibly. Here, we demonstrate rapid guest exchange between inclusion complexes of an open-window coordination cage that can simultaneously accommodate two guest molecules. Working with two types of guests, anthracene derivatives and BODIPY dyes, we show that the former can substantially modify the optical properties of the latter upon noncovalent heterodimer formation. We also studied the light-induced covalent dimerization of encapsulated anthracenes and found large effects of confinement on reaction rates. By coupling the photodimerization with the rapid guest exchange, we developed a new way to modulate fluorescence using external irradiation.

Excited state intramolecular proton transfer of 2-phenyl,3-hydroxybenzo[g]quinolones in solution and in G4 supramolecular hydrogels

The 2-Phenyl,3-Hydroxybenzo[g]quinolone (2P3HBQ) fluorophore and its derivative, 2-(4′-hydroxyphenyl)-3-hydroxybenzo[g]quinolone (2HP3HBQ),exhibit well-separated dual emission peaks attributable to Excited State Intramolecular Proton Transfer (ESIPT), thus offering promise as useful visible-absorbing ratiometric fluorescence probes. Time-resolved emission measurements in polar and H-bonding solvents reveal very long time-constants extending up to ∼2 ns, ostensibly associated with the ESIPT process, although the latter has traditionally been known to be ultra-fast for ordinary ESIPT molecules. These unusually long time-constants suggest that ESIPT of 2P3HBQ and 2HP3HBQ involves a large activation barrier, resulting from intermolecular H-bonding with the solvent. This is supported by temperature-dependent fluorescence studies, which show that the ESIPT rates in a polar solvent differ significantly over a range of temperatures, implying that solvent‧‧‧fluorophore intermolecular H-bonding is prevalent at lower temperatures but get disrupted at higher temperatures. Our studies were extended up to 2P3HBQ molecules incorporated inside G4 Supramolecular hydrogels via host–guest type non-covalent binding. ESIPT observed in the gels differ from that in solution state on several counts, reflecting the effect of confinement on the photophysics of the gel-bound fluorophores.

Confinement of Luminescent Guests in Metal-Organic Frameworks: Understanding Pathways from Synthesis and Multimodal Characterization to Potential Applications of LG@MOF Systems.

This review gives an authoritative, critical, and accessible overview of an emergent class of fluorescent materials termed “LG@MOF”, engineered from the nanoscale confinement of luminescent guests (LG) in a metal–organic framework (MOF) host, realizing a myriad of unconventional materials with fascinating photophysical and photochemical properties. We begin by summarizing the synthetic methodologies and design guidelines for representative LG@MOF systems, where the major types of fluorescent guest encompass organic dyes, metal ions, metal complexes, metal nanoclusters, quantum dots, and hybrid perovskites. Subsequently, we discuss the methods for characterizing the resultant guest–host structures, guest loading, photophysical properties, and review local-scale techniques recently employed to elucidate guest positions. A special emphasis is paid to the pros and cons of the various methods in the context of LG@MOF. In the following section, we provide a brief tutorial on the basic guest–host phenomena, focusing on the excited state events and nanoscale confinement effects underpinning the exceptional behavior of LG@MOF systems. The review finally culminates in the most striking applications of LG@MOF materials, particularly the “turn-on” type fluorochromic chemo- and mechano-sensors, noninvasive thermometry and optical pH sensors, electroluminescence, and innovative security devices. This review offers a comprehensive coverage of general interest to the multidisciplinary materials community to stimulate frontier research in the vibrant sector of light-emitting MOF composite systems.

Orthopaedic Sports Medicine Podcasts Should Tailor Characteristics Such as Episode Length and Social Media Utilization for Best Audience Engagement

PurposeTo describe the growth and characteristics of active orthopaedic sports medicine podcasts.MethodsThree common podcasting platforms (Apple, Google, and Spotify) were queried July 24, 2021 using the search term “sports medicine.” For each unique active podcast hosted by an orthopaedic surgeon, data were collected on year of the first episode, number of episodes, frequency of episodes, types of guests, topics discussed, episode length, and social media presence. Descriptive characteristics were then calculated.Results15 podcasts met inclusion criteria. Seven (46.7%) of these podcasts were started within 12 months of July 24, 2021. The most common episode release schedule was weekly, and podcast lengths averaged 21 minutes, 47 seconds (SD 17:17, range: 11:02–1:49:13). All podcasts featured guests, most often from a variety of sports medicine backgrounds. Social media platforms were commonly used by podcast hosts, with social media account follower numbers as high as over 100,000, and consistent engagement across three major social media platforms for most podcasts.ConclusionsThis study found that episodes are typically released weekly and average 21 minutes, 47 seconds long, with most covering a wide array of topics in sports medicine. The Facebook accounts of these podcasts displayed higher numbers of followers compared to other social media platforms; however, Instagram was superior for engagement.Clinical RelevanceOrthopaedic sports medicine podcasts have an increasing presence and can be used to increase trainee engagement and public exposure via tailoring of podcast episode lengths and selection of social media platforms with high audience interaction.

Multidimensional Mass Spectrometry Assisted Metallo-Supramolecular Chemistry

Multidimensional Mass Spectrometry Assisted Metallo-Supramolecular Chemistry

Design and control of axial binding with flexible Zn(II) porphyrin dimer: Building-up novel polymer with exo–endo binding

Pyrrole-bridged Zn(II) porphyrin dimer, Zn2DEP, has been utilized as an efficient tweezer host for the binding of guest (substrate) inside the cavity due to its large vertical flexibility. Aromatic monodentate substrate binds in an exo−endofashion to form a discrete monomeric complex while it converts to anexo−exo upon increasing the bulk of the guest. Shorter bidentate guest, on the other hand, forms 1:1 sandwich complex. In contrast, a longer bidentate guest binds in an exo−endo fashion but to form a polymeric structure. The complexes have been isolated in the solid state and structurally characterized while their complexation process in solution has been monitored spectroscopically. We also provide here a comprehensive account of the substrate binding ability of flexible Zn2DEP towards preferential formation of discrete monomeric exo–endo, exo–exo and sandwich complexes as well as 1D polymer just upon varying the size and type of axial guests. This work can contribute towards the rational design of receptors as highly efficient probes for molecular recognition and chirality sensing devices.

An Order–Disorder Type High‐Temperature Multiaxial Supramolecular Ferroelectric

AbstractMuch progress has been witnessed in exploring host–guest type ferroelectrics represented by ammonium‐crown ether compounds. However, the major obstacles in expanding their promising applications in nonvolatile memory elements, capacitors, and sensors are relatively low Curie temperature (Tc) and uniaxial attribute. Herein, by screening different organic cations and inorganic anions to assemble with 18‐crown‐6 molecule, it is found that a new ammonium‐crown ether inclusion ferroelectric 1, [(ATHTP)(18‐crown‐6)]BF4 (ATHTP = protonated 4‐aminotetrahydrothiopyran), undergoing a ferroelectric phase transition at a much higher Tc of 392 K which is comparable to BaTiO3 (Tc = 393 K). Notably, the distinct symmetry breaking, that is, 4/mmmFmm2, leads to a biaxial ferroelectric with four equivalent directions of polarization. Such high Tc and multiaxial nature are rare in existing crown ether‐based ferroelectrics. This work can help the exploration of high‐Tc multiaxial ferroelectrics toward further device applications.