Target Guests Research Articles

Predicting Online Complaining Behavior in the Hospitality Industry: Application of Big Data Analytics to Online Reviews

Purpose: This study aims to enrich the published literature on hospitality and tourism by applying big data analytics and data mining algorithms to predict travelers’ online complaint attributions to significantly different hotel classes (i.e., higher star-rating and lower star-rating). Design/methodology/approach: First, 1992 valid online complaints were manually obtained from over 350 hotels located in the UK. The textual data were converted into structured data by utilizing content analysis. Ten complaint attributes and 52 items were identified. Second, a two-step analysis approach was applied via data-mining algorithms. For this study, sensitivity analysis was conducted to identify the most important online complaint attributes, then decision tree models (i.e., the CHAID algorithm) were implemented to discover potential relationships that might exist between complaint attributes in the online complaining behavior of guests from different hotel classes. Findings: Sensitivity analysis revealed that Hotel Size is the most important online complaint attribute, while Service Encounter and Room Space emerged as the second and third most important factors in each of the four decision tree models. The CHAID analysis findings also revealed that guests at higher-star-rating hotels are most likely to leave online complaints about (i) Service Encounter, when staying at large hotels; (ii) Value for Money and Service Encounter, when staying at medium-sized hotels; (iii) Room Space and Service Encounter, when staying at small hotels. Additionally, the guests of lower-star-rating hotels are most likely to write online complaints about Cleanliness, but not Value for Money, Room Space, or Service Encounter, and to stay at small hotels. Practical implications: By utilizing new data-mining algorithms, more profound findings can be discovered and utilized to reinforce the strengths of hotel operations to meet the expectations and needs of their target guests. Originality/value: The study’s main contribution lies in the utilization of data-mining algorithms to predict online complaining behavior between different classes of hotel guests.

Size effect of graphene oxide sheets on enantioseparation performances in membrane separation

Recently, graphene oxide (GO)-based membranes have been demonstrated to be a potential candidate for gas purification and liquid separation techniques owing to their large surface area, tunable interactive sites, and adjustable interlayer spacing. Notably, GO-based membranes functionalized with chiral selectors have been demonstrated to possess high enantiomer permeability and impressive permeation selectivity toward enantiomeric target guests. However, the influence of the GO sheet size on the separation performance remains unclear. Here, we investigated the effect of the lateral size on the enantioseparation performances by modifying a chiral selector onto GO flakes with different sizes, considering that GO membranes possess an inherently high throughput character. In this work, three GO sheets with mean lateral sizes (~60, 650 and 4100 nm) were prepared, hereafter defined as GO1, GO2, and GO3, respectively. Then, a chemical modification of GO1, GO2 and GO3 with a chiral selector, L-Phenylalanine (L-Phe), yielded the corresponding L-Phe grafted GO sheets, L-Phe-GO1, L-Phe-GO2 and L-Phe-GO3. Finally, L-Phe-GO1, L-Phe-GO2 and L-Phe-GO3 membranes derived from a simple vacuum filtration method were employed to separate D-/L-phenylalanine. Results show that the L-Phe-GO3 based membrane allows for a remarkable chiral separation capacity, having a greatest enantioselectivity among three L-Phe-GO membranes with different lateral GO sizes. Our findings illustrate that the sheet size of GOs plays a dominant role in the enantioselectivity of membrane separation.

Tunable Fulleretic Sodalite MOFs: Highly Efficient and Controllable Entrapment of C60 Fullerene via Mechanochemistry

Encapsulation and confinement of fullerene guests in metal-organic frameworks (MOFs) lead to a novel class of crystalline fulleretic materials with unique physicochemical properties and a broad field of potential applications. The control over the amount of target guests confined in the MOF structure remains a significant challenge, which is particularly pronounced in the confinement of hardly accessible fullerene derivatives. The main strategies used in constructing fulleretic composites are limited by the solubility of components used and solvent versus guest competition for inhabitation of the framework voids. As mechanochemical procedures often overcome these issues, we developed here solvent-free processing by ball milling to gain control over the encapsulation of bulky and rigid C60-fullerene into a sodalite MOF with large cages and narrow cage-apertures. A rapid, green, efficient, and stoichiometry-controlled mechanochemical processing afforded four model C60@zeolitic-imidazolate framework 8 (ZIF-8) crystalline materials containing target 15, 30, 60, and 100 mol % of fullerene entrapped in the accessible cages of the model sodalite zeolitic-imidazolate framework 8 (ZIF-8), in stark contrast to the solution-based strategies that resulted in almost no loading. Varying the fullerene content affects the framework’s vibrational properties, color and luminescence of the composites, and the electron-dose radiation stability. The computational and spectroscopic studies show that the fullerene is accommodated in the cage’s center and that the cage-to-cage transport is a hardly feasible and energetically unfavored process. However, the fast release of C60 molecules from ZIF-8 can be effectively controlled by the pH. The entrapment of fullerene molecules in ZIF-8 resulted in their effective isolation even in higher loadings, paving the way to other tunable porous fulleretics containing single-molecule magnets or nanoprobes available on low scales.

Phenoxazine-based supramolecular tetrahedron as biomimetic lectin for glucosamine recognition

The design and synthesis of a phenoxazine-based metal-organic tetrahedron (Zn4L4) as biomimetic lectin for selectively recognition of glucosamine (GlcN) was reported. Different from the free phenoxazine-based ligand (L), Zn4L4 displayed the highest fluorescent intensity enhancement efficiency toward GlcN over other related natural mono- and disaccharides. Fluorescence titration demonstrated a 1:1 stoichiometric host-guest complex was formed with an association constant about 4.03 × 104 L/mol. 1H NMR spectroscopic studies confirmed this selectivity resulted from the multiple hydrogen bonding interactions formed between GlcN and Zn4L4. The present results suggested that rational arrangement of recognition sites in the confined space of metal-organic cage is crucial for the selectivity toward target guests.

Halal tourism: conceptual and practical challenges

PurposeMuslim tourists participating in halal tourism activities represent a valuable niche market for global tourism industry. The purpose of this study is to clarify the concepts of halal tourism and Islamic tourism and to draw attention to some conceptual and practical challenges in the halal tourism industry.Design/methodology/approachThe paper is based on a critical assessment of the literature in this field. To differentiate the concepts and to discuss practical and conceptual challenges, the authors found some references by reviewing the existing definitions in related literature and the primary source of the concepts which is Holy Book of Islam, Quran.FindingsThe terms “intention” and “Islamic motivation” can be used to differentiate Islamic tourism and halal tourism. The authors suggest calling hotels that provide good and services in halal tourism industry as “halal hotels” and tourists as “Muslim tourists”. One of the leading practical challenges in halal tourism is having lack of halal standards, especially for hotels. As the way Muslims understand and adapt their lives to Islam is quite different, which means this market is not homogenous, the authors suggest that halal hotels should be scaled through different qualifications in different countries.Research limitations/implicationsThis study is based on literature review, and it lacks primary research.Practical implicationsCurrent paper stresses the need for consistent use of Islamic-related tourism terms in industry. Hotel companies should have halal certifications that will provide assurance to customers. It is highly important for hotel companies to inform their target guests about the location of hotel before arriving at hotel. This is because halal hotels and other hotels are usually located in resort destination, especially in Turkey.Originality/valueThis paper is one of the leading papers that differentiates Islamic tourism and halal tourism concepts. It also provides several conceptual and practical issues in halal tourism industry.

The Smaller the Better: Hosting Trivalent Rare-Earth Guests in Cu–P Clathrate Cages

Summary The most striking difference between the trivalent rare-earth cations and their alkali and alkaline-earth peers is the presence of localized 4 f electrons. Placing trivalent rare-earth cations inside fullerene molecules or in between blocks of intermetallics has given rise to a plethora of fascinating properties and materials. A long-sought-after yet undiscovered material is a semiconducting compound with rare-earth cations situated inside the oversized polyhedral cages of a three-dimensional framework. In this work, we present a synthesis of unconventional clathrates, Ba 8−x R x Cu 16 P 30 , with the smallest pentagonal dodecahedral cages encapsulating La 3+ and Ce 3+ . Their composition and crystal structure were unambiguously determined by a combination of synchrotron powder diffraction, time-of-flight neutron powder diffraction, scanning transmission electron microscopy, and electron energy-loss spectroscopy. Our quantum-mechanical calculations and experimental characterizations show that the incorporation of the rare-earth cations significantly enhances hole mobility and reduces hole concentration, resulting in a drastic (700%) increase in the thermoelectric performance.

Selective binding of choline by a phosphate-coordination-based triple helicate featuring an aromatic box

In nature, proteins have evolved sophisticated cavities tailored for capturing target guests selectively among competitors of similar size, shape, and charge. The fundamental principles guiding the molecular recognition, such as self-assembly and complementarity, have inspired the development of biomimetic receptors. In the current work, we report a self-assembled triple anion helicate (host 2) featuring a cavity resembling that of the choline-binding protein ChoX, as revealed by crystal and density functional theory (DFT)-optimized structures, which binds choline in a unique dual-site-binding mode. This similarity in structure leads to a similarly high selectivity of host 2 for choline over its derivatives, as demonstrated by the NMR and fluorescence competition experiments. Furthermore, host 2 is able to act as a fluorescence displacement sensor for discriminating choline, acetylcholine, l-carnitine, and glycine betaine effectively.

Surface-Bound Cucurbit[8]uril Catenanes on Magnetic Nanoparticles Exhibiting Molecular Recognition.

We demonstrate the preparation of surface-bound cucurbit[8]uril (CB[8]) catenanes on silica nanoparticles (NPs), where CB[8] was employed as a tethered supramolecular "handcuff" to selectively capture target guest molecules. In this catenane, CB[8] was threaded onto a methyl viologen (MV(2+) ) axle and immobilized onto silica NPs. The formation of CB[8] catenanes on NPs were confirmed by UV/Vis titration experiments and lithographic characterization, demonstrating a high density of CB[8] on the silica NPs surface, 0.56 nm(-2) . This CB[8] catenane system exhibits specific molecular recognition towards certain aromatic molecules such as perylene bis(diimide), naphthol and aromatic amino acids, and thus it can act as a nanoscale molecular receptor for target guests. Furthermore, we also demonstrate its use as an efficient and recyclable nano-platform for peptide separation. By embedding magnetic NPs inside silica NPs, separation could be achieved by simply applying an external magnetic field. Moreover, the peptides captured by the catenanes could be released by reversible single-electron reduction of MV(2+) . The entire process demonstrated high recoverability.

Using water-mimic organic compounds to activate guest inclusion by initially dry beta-cyclodextrin

Optimal conditions were found enabling anhydrous beta-cyclodextrin (bCD) to include target guests using small monofunctional organic compounds instead of water.

Encapsulation of monoamine neurotransmitters and trace amines by amphiphilic anionic calix[5]arene micelles

The interactions between hydrochloride salts of biologically relevant amines and micelles formed by a water-soluble p-tert-butylcalix[5]arene were investigated by means of 1H NMR spectroscopy, using a combination of NOESY and DOSY techniques. DOSY measurements were conveniently employed to assess the micelle affinity towards the target guests (phenylethylamine ≈ histamine ≈ serotonin > tyramine > dopamine > norepinephrine), whereas NOESY studies revealed the approximate position of these cationic guests within the different micellar regions. In general, all the guests were located in the palisade region of the micelle, with the exception of phenethylamine and histamine, the former being bound to the micellar core as well as the palisade, the latter preferring the outer shell of the micelle.

ChemInform Abstract: Reversibly Expanded Encapsulation Complexes

AbstractReview: 92 refs.

Colorimetric sensing of pyrophosphate in aqueous media using bis-functionalised silica surfaces

Bis-functionalised silica surfaces have been designed in order to develop selective and sensitive probes for the chromo-fluorogenic detection of certain guests. The designed system consists of a siliceous support bis-functinalised with thiol and polyamine groups. Thiol groups are suitable reactive centres (R) that are know to react with squaraine dyes (D) inducing bleaching, whereas polyamines act as host sites (H) able to coordinate certain target guests (G). In the absence of G, the reactive groups (R) react with the dye resulting in a bleaching of the solution. On the contrary, the presence of certain guest (G) results in a control of the reaction kinetic between R and D and eventually in a complete reaction inhibition. Different functionalised solids were prepared by reaction of the siliceous surface with different concentrations of mercaptopropyltrimethoxysilane (MPTS) and 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (N3TS). The final materials (solids to ) were characterized employing standard procedures. In a first step the reactivity of the signaling dye D (squaraine ) with the reactive centre R (thiol groups) was studied as a function of the pH using solid that showed a most suitable response. At pH 7 and pH 5 there was a quick reaction between the squaraine and the thiol groups on the surface. On the contrary this reaction is significantly slower at pH 3 due to the different degree of protonation of the amines as a function of the pH. Additionally the reaction of with the squaraine has been studied in the presence of a range of inorganic anions with different structural dimensions and charges, including chloride, perchlorate, nitrate, sulfate, phosphate and pyrophosphate. At pH 3 the reaction of the dye with the thiol groups is still effective in the presence of chloride and perchlorate, but the reaction is highly inhibited in the presence of the anions nitrate, sulfate, phosphate and pyrophosphate. At pH 7 the squaraine reacts very fast with the thiol groups in the presence of all the anions studied. In contrast, at pH 5 only pyrophosphate is able to inhibit, to a certain extent, the reaction of the squaraine with the thiols, resulting in a selective chromo-fluorogenic detection of this anion in pure water. Finally, the observed behaviour was discussed in terms of both, the kinetic rates of the reaction between the thiol and the squaraine groups and the thermodynamic interaction reaction between the anions and the polyamine moieties.

Anchoring Dyes into Multidimensional Large‐Pore Zeolites: A Prospective Use as Chromogenic Sensing Materials

A versatile procedure for anchoring dyes into the pores of multidimensional zeolites by including organic dye precursors in the synthesis gel has been developed. To prove the concept, an aniline-functionalised zeolite Beta was obtained by reaction of triethylorthosilicate (TEOS), tetraethylammonium hydroxide, and N-methyl,N-(propyl-3-trimethoxysilyl)aniline (MPTMSA) in the presence of HF. Further extraction of the structure-directing agents resulted in a highly crystalline, white, functionalised zeolite Beta containing anchored aniline groups. Similar organic functionalised molecular sieves (OFMS) have been explored as novel catalysts, but, as far as we know, OFMS have never been used as precursors for dye-immobilisation or to design new solid-based host systems for selective molecular sensing processes as is reported here. In a second step the solids containing dyes were prepared by reaction of the hybrid material with the appropriate reactives to obtain tricyanovinylbenzene, triphenylpyrylium, azoic, and squaraine derivatives. All these reactions are straightforward and involve electrophilic aromatic substitution or diazotisation reactions at the electron-rich aniline ring. The final dye-functionalised solid materials were isolated by simple filtration and washing procedures and have been characterised by a number of techniques. In all cases the Beta structure of the solid remains unaltered. Among the large number of areas where dye-containing zeolites might be of importance, we were interested in testing their unconventional use as heterosupramolecular hosts in chromogenic protocols. To check their potential use as chemosensors, microporous solids with anchored triphenylpyrilium and squaraine dyes were selected and used as sensors for the chromogenic discrimination of amines. It was found that the response of both solids to amines was basically governed by the three-dimensional (3D) solid architecture that tuned the intrinsic unselective reactivity of the pyrylium dye. By using new solid-state supramolecular chemistry protocols we believe that these, and similar future dye-zeolite hosts, might be promising new sensor materials allowing the visible discrimination of selected target guests by size and/or polarity within families or closely related molecules.

Squaraines as fluoro-chromogenic probes for thiol-containing compounds and their application to the detection of biorelevant thiols.

A highly selective colorimetric chemodosimeter for thiol-containing compounds in aqueous solutions is reported. The design protocol makes use of a highly specific reaction between thiols and the electrophilic four-membered ring of highly colored, fluorescent squaraine backbones. At neutral pH selective decoloration and total emission quenching was found due to the rupture of the highly delocalized squaraine framework upon selective nucleophilic addition of thiol-containing derivatives. The squaraine derivatives have been successfully applied to the determination of low-molecular mass aminothiols in human plasma. The method utters the high potential applicability of the chemodosimeter approach in the search for new or improved chromogenic selective or specific probes for target guests.

Competitive Inclusion of Binary Flavor Mixtures in .ALPHA.-, .BETA.- and .GAMMA.-Cyclodextrin.

The inclusion of binary liquid flavor such as phenyl ethanol/d-limonene or methyl n-hexanoate/d-limonene into α-, β- and γ-cyclodextrin was investigated. The inclusion of the target guests (phenyl ethanol and methyl n-hexanoate) was inhibited by the presence of the inhibitor, d-limonene. Three types of inhibited inclusion were observed depending on the combination between cyclodextrins and the binary liquid flavors. The inclusion fractions of the target compounds (the molar ratio of the included target guest to cyclodextrin) were correlated by the inhibited enzyme kinetic equation of Michaelis–Menten type, which commonly used to analyze the inhibition of the enzymatic reactions. At the higher concentrations of the target guest, the competitive inclusion model could correlate the inclusion fraction independent of the type of cyclodextrin. However, at a low concentration, the presence of d-limonene inhibited the inclusion of the target guests in a noncompetitive manner for α- and β-cyclodextrin and in an uncompetitive manner for γ-cyclodextrin, respectively.

Molecularly Imprinted Cyclodextrins as Selective Receptors for Steroids

β-Cyclodextrin (β-CyD) was cross-linked by toluene 2,4-diisocyanate in the presence of various steroids in dimethyl sulfoxide, and the steroids were removed after the polymerization. The molecularly imprinted β-CyD polymer, obtained by using cholesterol or stigmasterol as the template, efficiently and reversibly bound the steroid in the mixtures of water and tetrahydrofuran. In these polymers, the mutual orientation of β-CyD molecules is regulated so that they cooperatively bind the target guests which are too large to be included in the cavity of one β-CyD molecule. When either the alkyl residue at the 17-position or the hydroxyl residue at the 3-position is absent from the template, however, the molecular imprinting is much less efficient. The mechanism for the imprinting and the structure of the guest-binding sites in the imprinted polymers have been proposed.

Molecular Recognition Based on Membrane Potential Changes Induced by Host–Guest Complexation with Inorganic and Organic Guests

Guest-induced changes in membrane potentials are one of the representative modes of electrochemical signal transduction by molecular recognition at the interface of an organic membrane and an aqueous solution. Recent approaches based on synthetic hosts capable of effecting membrane potential changes by host–guest complexation with inorganic and organic guests are described. Although the studies in this area have mainly been aimed at inorganic cations as the target guests, recent approaches for recognition of inorganic anions and further organic guests are also documented. Highly selective changes in membrane potentials can be achieved for inorganic cations by sophisticated design of crown ethers and related compounds. Hosts with complementary charge(s) or multiple hydrogen bonding sites are effective for the recognition of inorganic anions and also of the polar moieties of organic ions. On the other hand, the recognition of nonpolar moieties of organic guests can be achieved by inclusion into well-defined cavities of host molecules. Quaternary onium and protonated amine salts are recently found to be capable of effecting membrane potential changes by complexation with neutral phenolic guests.

Molecular recognition of dihydroxyaromatics with bis-o-xylyleneglycoluril hosts

Abstract