Excitation-Wavelength-Dependent Luminescence of Chemically and Physically Mixed Europium and Terbium Phosphonates: Color-Tunable Luminescence, Near-White-Light Emission, and Selective Fe3+ Detection.

Molecular lanthanide phosphonates [Ln2 (H3 tpmm)2 (H2 O)6 ] ⋅ xH2 O (Ln=Eu, EuP; Ln=Tb, TbP) were synthesized. Single-crystal X-ray diffraction confirmed that EuP has a sandwich-like dinuclear structure, in which the Eu(III) center adopts a {EuO8 } distorted dodecahedral geometry. XRPD patterns prove that TbP and EuP are isomorphous and isostructural. EuP and TbP are highly thermally stable approaching 450 °C and exhibit red- and green-light emissions from the characteristic 4 f-4 f transition of the Eu3+ and Tb3+ , respectively. Interestingly, luminescence modulation is achieved for the chemically mixed Eu/Tb phosphonate analogues, c-Eux Tb2 -x P (x=1.5, 1, 0.5), and physically mixed Eu/Tb phosphonate materials, p-yEuP : zTbP (y : z=3 : 1, 1 : 1, 1 : 3), with varying the excitation wavelength. Of particular note, near-white-light emission is also achieved for c-EuTbP, p-EuP : TbP, and p-EuP : 3TbP when excited at 365 nm. Therefore, these dinuclear molecular lanthanide phosphonates emitting excitation wavelength and Eu3+ : Tb3+ ratio dependent luminescence might be potential candidates for color-tunable luminescence materials and white-light-emitting materials. On the other hand, the bright green-light emission makes TbP to be an excellent reusable luminescence sensor for selective detection of Fe3+ with Stern-Volmer quenching constant (KSV ) of 9.66×103  M-1 and detection limit (DL) of 0.42 µM through absorption competition caused luminescence quenching effect.

Zinc(II)-Based Ring-and-Rod Coordination Layer as an Excitation-Wavelength-dependent Dual-Emissive Chemosensor for Discriminating Fe3+, Cr3+, and Al3+ in Water.

The reactions of Zn(NO3)2, 3,6-bis(pyridin-3-yl)-9H-carbazole (bpycz), and 2,5-dihydroxyterephthalic acid (H4dhbdc) or 2-bromoterephthalic acid (Br-1,4-H2bdc) under hydro(solvo)thermal conditions yielded corresponding coordination polymers (CPs) {[Zn(H2dhbdc)(bpycz)]•0.5H2O}n (1) and [Zn(Br-1,4-bdc)(bpycz)]•2DMAc•H2O (2), respectively, with high thermal stability approaching 350 °C. CP 1 adopts a ring-and-rod layer structure, which is topologically described as a 4-connected net with the point symbol of 2•65. Two layers are interpenetrated in parallel interlocking mode to form a double 2D → 2D polyrotaxane entanglement with extra-framework void space of 19.6%. CP 2 has a non-interpenetrating ring-and-rod layer structure of 4-connected 2•65 net topology, with extra-framework void space of 16.6%. Thermally activated 1 and 2 revealed CO2 uptakes of 101.1 and 98.6 cm3 g-1, respectively, at P/P0 = 1 and 195 K. X-ray powder diffraction (XRPD) patterns confirmed that 1 and 2 both possessed high chemical stability in H2O, CH3OH, acetone, and DMF, and framework stability during gas adsorption-desorption. The H2O suspension of 1 displayed excitation-dependent dual-emissive properties, appearing at 432 nm upon excitation at 300 nm and at 528 nm upon excitation at 365 nm. Of note, 1 was capable of detection of Fe3+, Cr3+, and Al3+ ions in H2O, showing good anti-interference ability, excellent selectivity, and high sensitivity. More interesting, the dual-emissive properties make 1 to be an excellent luminescence chemosensor to screen Fe3+, Cr3+, and Al3+ from a pool of metal ions in H2O upon excitation at 300 nm via luminescence quenching effect and then discriminate Fe3+, Cr3+, and Al3+ upon excitation at 365 nm via luminescence quenching, unaltered, and enhancement responses, respectively. On the other hand, the H2O suspension of 2 demonstrated an excitation-independent emission appearing at around 430 nm, which could be utilized to sensitively detect Fe3+ and Cr3+ ions with good anti-interference ability and excellent selectivity via luminescence quenching effect. Further, 1 and 2 were recyclability and possessed cycling stability. The plausible sensing mechanisms for 1 and 2 toward Fe3+, Cr3+, and Al3+ were also explored in detail.

Engineered Bifunctional Luminescent Pillared-Layer Frameworks for Adsorption of CO2 and Sensitive Detection of Nitrobenzene in Aqueous Media.

Through a dual-ligand synthetic approach, five isoreticular primitive cubic (pcu)-type pillared-layer metal-organic frameworks (MOFs), [Zn2 (dicarboxylate)2 (NI-bpy-44)]⋅x DMF⋅y H2 O, in which dicarboxylate=1,4-bdc (1), Br-1,4-bdc (2), NH2 -1,4-bdc (3), 2,6-ndc (4), and bpdc (5), have been engineered. MOFs 1-5 feature twofold degrees of interpenetration and have open pores of 27.0, 33.6, 36.8, 52.5, and 62.1 %, respectively. Nitrogen adsorption isotherms of activated MOFs 1'-5' at 77 K all displayed type I adsorption behavior, suggesting their microporous nature. Although 1' and 3'-5' exhibited type I adsorption isotherms of CO2 at 195 K, MOF 2' showed a two-step gate-opening sorption isotherm of CO2 . Furthermore, MOF 3' also had a significant influence of amine functions on CO2 uptake at high temperature due to the CO2 -framework interactions. MOFs 1-5 revealed solvent-dependent fluorescence properties; their strong blue-light emissions in aqueous suspensions were efficiently quenched by trace amounts of nitrobenzene (NB), with limits of detection of 4.54, 5.73, 1.88, 2.30, and 2.26 µm, respectively, and Stern-Volmer quenching constants (Ksv ) of 2.93×103 , 1.79×103 , 3.78×103 , 4.04×103 , and 3.21×103 m-1 , respectively. Of particular note, the NB-included framework, NB@3, provided direct evidence of the binding sites, which showed strong host-guest π-π and hydrogen-bonding interactions beneficial for donor-acceptor electron transfer and resulting in fluorescence quenching.

A Cd(II) Luminescent Coordination Grid as a Multiresponsive Fluorescence Sensor for Cr(VI) Oxyanions and Cr(III), Fe(III), and Al(III) in Aqueous Medium.

Hydro(solvo)thermal reactions of Cd(NO3)2, N-(pyridin-3-ylmethyl)-4-(pyridin-4-yl)-1,8-naphthalimide (NI-mbpy-34), and 5-bromobenzene-1,3-dicarboxylic acid (Br-1,3-H2bdc) afforded a luminescent coordination polymer, {[Cd(Br-1,3-bdc)(NI-mbpy-34)(H2O)]∙2H2O}n (1). Single-crystal X-ray diffraction analysis showed that 1 features a two-dimensional (2-D) gridlike sql layer with the point symbol of (44·62), where the Cd(II) center adopts a {CdO5N2} pentagonal bipyramidal geometry. Thermogravimetric (TG) analysis confirmed the thermal stability of 1 up to about 340 °C, whereas XRPD patterns proved the maintenance of crystallinity and framework integrity of 1 in CH2Cl2, H2O, CH3OH, and toluene. Photoluminescence studies indicated that 1 displayed intense blue fluorescence emissions in both solid-state and H2O suspension-phase. Owing to the good fluorescent properties, 1 could serve as an excellent turn-off fluorescence sensor for selective and sensitive Cr(VI) detection in water, with LOD = 15.15 µM for CrO42- and 14.91 µM for Cr2O72-, through energy competition absorption mechanism. In addition, 1 could also sensitively detect Cr3+, Fe3+, and Al3+ ions in aqueous medium via fluorescence-enhancement responses, with LOD = 2.81 µM for Cr3+, 3.82 µM for Fe3+, and 3.37 µM for Al3+, mainly through an absorbance-caused enhancement (ACE) mechanism.

Fluorescent Cadmium Bipillared-Layer Open Frameworks: Synthesis, Structures, Sensing of Nitro Compounds, and Capture of Volatile Iodine.

Fluorescent Cd metal-organic frameworks (MOFs), [Cd2 (dicarboxylate)2 (NI-bpy-44)2 ] (dicarboxylate=benzene-1,4-dicarboxylate (1,4-bdc, 1), 2-bromobenzene-1,4-dicarboxylate (Br-1,4-bdc, 2), 2-nitrobenzene-1,4-dicarboxylate (NO2 -1,4-bdc, 3), biphenyl-4,4'-dicarboxylate (bpdc, 4); NI-bpy-44=N-(pyridin-4-yl)-4-(pyridin-4-yl)-1,8-naphthalimide)), featuring non- and twofold interpenetrating pcu-type bipillared-layer open structures with sufficient free voids of 58.4, 51.4, 51.5, and 41.4 %, respectively, have been hydro(solvo)thermally synthesized. MOFs 1-4 emitted solid-state blue or cyan fluorescence emissions at 447±7 nm, which mainly arose from NI-bpy-44 and are dependent on the incorporated solvents. After immersing the crystalline samples in different solvents, that is, H2 O and DMSO (1 and 2) as well as nitrobenzene and phenol (1-4), they exhibited a remarkable fluorescence quenching effect, whereas o-xylene and p-xylene (4) caused significant fluorescence enhancement. The sensing ability of MOFs 1-4 toward nitro compounds carried out in the vapor phase showed that nitrobenzene and 2-nitrophenol displayed detectable fluorescence quenching with 1, 2, and 4 whereas 4-nitrotoluene was an effective fluorescence quencher for 1 and 2; this is most likely attributed to their electron-deficient properties and higher vapor pressures. Moreover, MOFs 1-4 are highly reusable for quick capture of volatile iodine, as supported by clear crystal color change and also by immense fluorescence quenching responses owing to the donor-acceptor interaction. Low-pressure CO2 adsorption isotherms indicate that activated materials 1'-4' are inefficient at taking up CO2 .

Converting Nonliquid Crystals into Liquid Crystals by N-Methylation in the Central Linker of Triazine-Based Dendrimers.

Two triazine-based dendrimers were successfully prepared in 60-75% yields. These newly prepared dendrimers 2a and 2b containing the -NMe(CH2)2NMe- and the -NMe(CH2)4NMe- linkers between two G3 dendrons, respectively, exhibit columnar phases during the thermal process. However, the corresponding dendrimers 1a and 1b containing the -NH(CH2)2NH- and the -NH(CH2)4NH- linkers between two G3 dendrons, respectively, do not show any LC phases on thermal treatment. Computational investigations on molecular conformations reveal that N-methylation of the dendritic central linker leads dendrimers to possess more isomeric conformations and thus successfully converts non-LC dendrimers (1a and 1b) into LC dendrimers (2a and 2b).

Infinite copper(II) coordination architectures from a resonative aminotriazine-derived tripodal ligand: synthesis, structures, and magnetic properties.

The ligand 2,4,6-tris(2-picolylamino)-1,3,5-triazine (o-H3tpat) with essentially resonative structure and two copper(II)-based one-dimensional coordination chain structures, [Cu3Cl5(o-H2tpat)(H2O)]·MeOH·CH2Cl2 (1) and [Cu2(o-H2tpat)(H2O)(MeOH)(NO3)2](NO3)·3MeOH (2), with different structural patterns have been synthesized and characterized using single crystal X-ray diffraction analysis. For o-H3tpat, two crystalline forms showing different solid-state structural features are obtained from MeOH/Et2O (form I) and CH2Cl2/Et2O (form II), respectively. The o-H3tpat form I adopts an asymmetric-configured all-amino resonative tautomer with three cis-trans-trans-arranged pyridyl groups, whereas the o-H3tpat form II adopts also an identical resonative structure but where two of the three pyridyl groups are in a cis-manner and the third one is nearly coplanar with the central aminotriazine core. On the other hand, the designed tripodal ligand in both Cu(II)-complexes serves as a monoanion, o-H2tpat(-), which suits a propeller-configured all-imino resonative structure in 1 and a syn-anti-configured amino-imino-imino resonative structure in 2. These observations significantly indicate that the o-H3tpat ligand can self-adjust and interconvert its conformation via a possible structure transformation associated with proton-shift to adapt a change in the crystallization and self-assembly reaction systems. In the magnetic point of view, 1 is treated as repeated chains composed of infinite {Cu6Cl10} units wherein the hexanuclear unit is further decomposed to one {Cu(II)4Cl6} and two magnetically isolated {Cu(II)Cl2} subunits. Antiferromagnetic interactions are found for the Cu4 subunits (g = 2.33, 2J1 = -5.6 cm(-1), 2J2 = -8.6 cm(-1), 2J3 = -4.1 cm(-1), and J4 held to zero). For 2, it is considered as an infinite chain that composes of Cu2 units antiferromagnetically coupled (g = 2.03, 2J1 = -0.2 cm(-1)). The small antiferromagnetic exchange constants in both 1 and 2 suggest that the unpaired spins do not effectively interact through the tripodal o-H2tpat(-) ligands.

A Water-Stable 2-Fold Interpenetrating cds Net as a Bifunctional Fluorescence-Responsive Sensor for Selective Detection of Cr(III) and Cr(VI) Ions.

Reactions of ZnSO4∙7H2O, N-(pyridin-3-ylmethyl)-4-(pyridin-4-yl)-1,8-naphthalimide (NI-mbpy-34), and 5-bromobenzene-1,3-dicarboxylic acid (Br-1,3-H2bdc) afforded a luminescent coordination polymer, [Zn(Br-1,3-bdc)(NI-mbpy-34)]n (1), under hydro(solvo)thermal conditions. Single-crystal X-ray structure analysis revealed that 1 features a three-dimensional (3-D) 2-fold interpenetrating cds (or CdSO4) net topology with the point symbol of (65·8), where the Zn(II) centers are considered as 4-connected square-planar nodes. X-ray powder diffraction (XRPD) patterns and thermogravimetric (TG) analysis confirmed that 1 shows high chemical and thermal stabilities. Notably, 1 displayed solvent dependent photoluminescence properties; the fluorescence intensity and emission maximum of 1 in different solvent suspensions varied when a solvent was changed. Furthermore, the H2O suspension of 1 exhibited blue fluorescence emission and thus can be treated as a selective and sensitive fluorescent probe for turn-on detection of Cr3+ cations through absorbance caused enhancement (ACE) mechanism and turn-off detection of Cr2O72-/CrO42- anions through collaboration of the absorption competition and energy transfer process, with limit of detection (LOD) as low as µM scale.

Visual behavior patterns of successful decision makers in crime scene photo investigation: An eye tracking analysis.

Crime scene investigation serves as an important source of information for law enforcement officers when running a case. Effective leads are uncovered based on the knowledge, technique, and experience of the crime scene investigator. This study utilized eye-tracking technology to understand different decision makers'visual behaviors and decision-making process when studying a crime scene picture. A total of 42 college students majored in crime investigation were recruited as the subjects of the study. Eye movement data were collected and analyzed using t-test and ANOVA on eye-tracking measures of areas of interest (AOI) for visual attention distributions as well as lag sequence analysis (LSA), heat map, and scan path observations for visual transfer patterns. The results showed that participants who made the correct decision were faster in identifying the key target. Regardless of whether they made the correct decision or not, their visual attention was fixated on the answer option of their choosing. Additionally, the subjects' attention must be shifted to the key target in order to make the correct decision. This study successfully applied the eye-tracking method to explore the investigation and decision-making process of inspecting a crime scene picture. Future studies can apply the eye-tracking method to deeply understand the process of information processing in investigating criminal scene pictures and provide more suggestions for professional training curriculum and instruction.

A Systematic Review of MRI Neuroimaging for Education Research.

This study aims to disclose how the magnetic resonance imaging (MRI) neuroimaging approach has been applied in education studies, and what kind of learning themes has been investigated in the reviewed MRI neuroimaging research. Based on the keywords "brain or neuroimaging or neuroscience" and "MRI or diffusion tensor imaging (DTI) or white matter or gray matter or resting-state," a total of 25 papers were selected from the subject areas "Educational Psychology" and "Education and Educational Research" from the Web of Science and Scopus from 2000 to 2019. Content analysis showed that MRI neuroimaging and learning were studied under the following three major topics and nine subtopics: cognitive function (language, creativity, music, physical activity), science education (mathematical learning, biology learning, physics learning), and brain development (parenting, personality development). As for the type of MRI neuroimaging research, the most frequently used approaches were functional MRI, followed by structural MRI and DTI, although the choice of approach was often motivated by the specific research question. Research development trends show that the neural plasticity theme has become more prominent recently. This study concludes that in educational research, the MRI neuroimaging approach provides objective and empirical evidence to connect learning processes, outcomes, and brain mechanisms.

Anion-Dominated Copper Salicyaldimine Complexes-Structures, Coordination Mode of Nitrate and Decolorization Properties toward Acid Orange 7 Dye.

A salicyaldimine ligand, 3-tert-butyl-4-hydroxy-5-(((pyridin-2-ylmethyl)imino)methyl)benzoic acid (H2Lsalpyca) and two Cu(II)-salicylaldimine complexes, [Cu(HLsalpyca)Cl] (1) and [Cu(HLsalpyca)(NO3)]n (2), have been synthesized. Complex 1 has a discrete mononuclear structure, in which the Cu(II) center is in a distorted square-planar geometry made up of one HLsalpyca- monoanion in an NNO tris-chelating mode and one Cl- anion. Complex 2 adopts a neutral one-dimensional zigzag chain structure propagating along the crystallographic [010] direction, where the Cu(II) center suits a distorted square pyramidal geometry with a τ value of 0.134, consisted of one HLsalpyca- monoanion as an NNO tris-chelator and two NO3- anions. When the Cu∙∙∙O semi coordination is taken into consideration, the nitrato ligand bridges two Cu(II) centers in an unsymmetrical bridging-tridentate with a µ, κ4O,O':O',O″ coordination. Clearly, anion herein plays a critical role in dominating the formation of discrete and polymeric structures of copper salicyaldimine complexes. Noteworthy, complex 2 is insoluble but highly stable in H2O and various organic solvents (CH3OH, CH3CN, acetone, CH2Cl2 and THF). Moreover, complex 2 shows good photocatalytic degradation activity and recyclability to accelerate the decolorization rate and enhance the decolorization performance of acid orange 7 (AO7) dye by hydrogen peroxide (H2O2) under daylight.

From lamellar net to bilayered-lamella and to porous pillared-bilayer: reversible crystal-to-crystal transformation, CO2 adsorption, and fluorescence detection of Fe3+, Al3+, Cr3+, MnO4-, and Cr2O72- in water.

An aqua-coordinated lamellar net [Zn(5-NH2-1,3-bdc)(H2O)] (1, 5-NH2-1,3-H2bdc = 5-amino-1,3-benzenedicarboxylic acid) has been found to undergo a reversible stimuli-responsive 2D-to-2D crystal-to-crystal transformation with a water-free bilayered-lamellar net [Zn(5-NH2-1,3-bdc)] (1') upon removal and rebinding of aqua ligands, whereas a 2D porous pillared-bilayer [Zn2(5-NH2-1,3-bdc)2(NI-bpy-44)]·DMF (2, NI-bpy-44 = N-(pyridin-4-yl)-4-(pyridin-4-yl)-1,8-naphthalimide) has been tailored by introducing NI-bpy-44 to replace the coordinated aqua ligands. Pillared-bilayer 2 displayed a moderate CO2 uptake of 79.1 cm3 g-1 STP at P/P0 = 1 and 195 K with an isosteric heat of CO2 adsorption (Qst) of 37.0 kJ mol-1 at zero-loading. It is noteworthy that the water suspensions of 1 and 2 both displayed good fluorescence performances, which were effectively quenched by Fe3+, MnO4-, and Cr2O72- ions and shifted to long wavelengths by Fe3+, Al3+, and Cr3+, even with the coexistence of equal amounts of most other interfering ions. Taking the Stern-Volmer quenching constant, limit of detection, quenching efficiency, anti-interference ability, and visual observation into consideration, it is clear that both 1 and 2 are promising and excellent fluorescent sensors for highly sensitive detection of Fe3+, MnO4-, and Cr2O72-.

Two-fold 2D + 2D → 2D interweaved rhombus (4,4) grid: synthesis, structure, and dye removal properties in darkness and in daylight.

Compound [Cu(NI-mbpy-44)2(NO3)2]·4H2O (1, NI-mbpy-44 = N-(pyridin-4-ylmethyl)-4-(pyridin-4-yl)-1,8-naphthalimide) adopting a two-dimensional (2D) periodical rhombus (4,4) grid has been synthesized. This grid doubly interweaves in a parallel fashion to result in overall 2D + 2D → 2D networks with approximately 14% sufficient free volumes in which lattice H2O molecules reside. Dye removal studies show that 1 selectively adsorbs anionic methyl orange (MO) and acid orange 7 (AO7) over cationic methylene blue (MB) and malachite green (MG) from aqueous solutions containing single or mixed dyes in darkness at room temperature. The experimental isotherm data were analyzed using linear Langmuir and Freundlich isotherm equations; the results indicated that the Langmuir model showed a better fit for the adsorption of MO and AO7 over 1, with high dark adsorption capacities of 810 and 370 mg g-1, respectively, although there could also be other associated mechanisms. The dark adsorption kinetics of MO and AO7 over 1 obeyed the pseudo-second-order kinetic model. Electrostatic attraction appears to be the dominating mechanism for adsorptive removal of MO and AO7 by 1, whereas π-π stacking (MO and AO7) and hydrogen-bonding interactions (AO7) could also be responsible. Exploration of the adsorption performance of MO and AO7, including studying the kinetics in daylight, shows similar results to those obtained in darkness, indicating the negligible influence of daylight on the dye removal. Nevertheless, 1 could liberate NI-mbpy-44 and Cu(ii) into water throughout the entire adsorption experiment, which could be a potential environmental hazard, this could cause secondary pollution and mean that 1 is impractical for use as an adsorbent candidate.

Synthesis, Structure, and Dye Adsorption Properties of a Nickel(II) Coordination Layer Built from d-Camphorate and Bispyridyl Ligands.

Reaction of NiCl2∙6H2O, d-camphoric acid (d-H2cam), and N,N'-bis(pyraz-2-yl)piperazine (bpzpip) in pure water at 150 °C afforded a novel nickel(II) coordination layer, [Ni4(d-cam)2(d-Hcam)4(bpzpip)4(H2O)2] (1), under hydro(solvo)thermal conditions. Single-crystal X-ray structure analysis reveals that 1 adopts a six-connected two-dimensional (2D) chiral layer structure with 36-hxl topology. Dye adsorption explorations indicate that 1 readily adsorbs methyl blue (MyB) from water without destruction of crystallinity. On the contrary, methyl orange (MO) is not adsorbed at all. The pseudo-second-order kinetic model could be used to interpret the adsorption kinetics for MyB. Equilibrium isotherm studies suggest complicated adsorption processes for MyB which do not have good applicability for either the two-parameter Langmuir or Freundlich isotherm model. The saturated adsorption capacity of 1 for MyB calculated by Langmuir is 185.5 mg·g-1 at room temperature.