Honeycomb Topology Research Articles

Dopamine Sensing Based on Ultrathin Fluorescent Metal-Organic Nanosheets.

The importance of dopamine (DA) detection as a biomarker for several diseases, especially Parkinson''s disease, has persuaded scientists to develop new nanomaterials for efficient sensing of DA in clinical samples. Ultrathin metal-organic nanosheets due to their exceptional thickness, large surface area, and flexibility are endowed with many accessible active sites and optimal surface interaction with the target analyte molecules. In this regard, a novel layered fluorescent metal-organic nanomaterial with a honeycomb topology based on europium, [Eu(pzdc)(Hpzdc)(H2O)]n (ECP) (H2pzdc = 2,3-pyrazine dicarboxylic acid), was synthesized. X-ray crystallography revealed that the 3D supramolecular architecture of ECP is constructed from noncovalent interactions of coordinated water molecules between the 2D layers along the b axis. These layers that are only ∼4 nm thick were conveniently separated through ultrasound-induced liquid phase exfoliation. Optical studies show that the reduction of ECP thickness enhances the fluorescence intensity and serves as an efficient optical marker for DA detection. ECP nanoflakes exhibited fast response and high selectivity for DA detection in clinical samples. Good linearity for DA detection in the range of 0.1-10 μM with a detection limit of 21 nM proves the potential of ECP nanoflakes in DA sensing applications.

Uranyl Tricarballylate Triperiodic and Nanotubular Species. Counterion Control of Nanotube Diameter.

Tricarballylic acid (propane-1,2,3-tricarboxylic acid, H3 tca) was reacted with uranyl nitrate hexahydrate under solvo-hydrothermal conditions and in the presence of different additional cations, yielding four complexes which have been crystallographically characterized. [(UO2)2Ba(tca)2(H2O)4] (1), isomorphous to the PbII analogue previously reported, crystallizes as a triperiodic framework in which diperiodic uranyl-tca3- subunits with the hcb (honeycomb) topology are linked by carboxylate-bound BaII cations. Triperiodic polymerization is also found in [(UO2)2(tca)2Ni(cyclam)] (2) and [(UO2)2(tca)2Cu(R,S-Me6cyclam)] (3), but here the diperiodic uranyl-tca3- subunits have the sql (square lattice) topology, and the frameworks formed through bridging by NiII or CuII cations have different topologies, tcs in 2 and xww in 3. [Co(en)3][UO2(tca)]3·2H2O (4) crystallizes as a monoperiodic coordination polymer with the hcb topology and a nanotubular geometry. In contrast to the square-section nanotubules previously found in [NH4][(UO2)2Pb(tca)2(NO3)(bipy)] (bipy = 2,2'-bipyridine), those in 4 have a hexagonal section with a width of ∼7 Å. The structure-directing role of the hydrogen bonded counterions in these nanotubular species, either NH4+ located within the nanotubule cavity or [Co(en)3]3+ located outside, is discussed. Emission spectra in the solid state display the usual vibronic fine structure for 1 and 4, while uranyl emission is quenched in 3.

A Novel TDMA-Based Fault Tolerance Technique for the TSVs in 3D-ICs Using Honeycomb Topology

Through-silicon-vias (TSVs) are prone to defects during the manufacturing process, which pose yield challenges for three dimensional integrated circuits (3D-ICs). The area per TSV is too great to be ignored, and in order to not use any redundant TSVs, a chain-type time division multiplexing access (TDMA)-based fault tolerance technique is proposed. However, a double-TSV structure is used per group, resulting in a significant TSV hardware overhead under a given large-scaled circuit design. Furthermore, it is impossible for the chain-TDMA scheme to plan the rerouting path for the right-hand-most TSV per group, resulting in a decrease in the repair rate per TSV group as well as in the whole TSV yield. In the proposed technique, we bundle six TSVs per group in a honeycomb pattern and the TSVs on the edges are connected to each other, enhancing the repair rate per group as well as the whole TSV yield. Subsequently, an architecture based on the proposed technique is designed, evaluated, and validated on logic-on-logic 3D IWLS'05 benchmark circuits using 45 nm TSMC technology. The proposed technique is found to reduce the area overhead by 87.95-90.42 percent, compared to the chain-TDMA scheme, which results in a yield of 96.90-99.09 percent.

Study of four new Cd(II) metal-organic frameworks: Syntheses, structures, and highly selective sensing for 4-nitrophenol

Four new mixed ligand based metal-organic frameworks (MOFs), devised as [Cd(AA)(bpa)(OH2)]n (MOF-AA), [Cd(PA)(bpa)]n (MOF-PA), {[Cd(SUA)(bpa)].CH3OH}n (MOF-SUA) and {[Cd(AzA)(bpa)].2CH3OH}n (MOF-AzA) (where, AA = adipic acid; PA = pimelic acid; SUA = suberic acid; AzA = azelaic acid; bpa = 1,2-bis(4-pyridyl)ethane) have been synthesized, and successfully identified by elemental analyses, FT-IR, powder X-ray diffraction, single-crystal X-ray diffraction, and thermal analyses. MOF-AA exhibits 3D coordination network with new honey comb topology (4-c, uninodal net), while MOF-PA shows 2D structure with hxl/Shubnikov plane net topology (6-c, uninodal net). MOF-SUA and MOF-AzA display 2D frameworks with sql/Shubnikov tetragonal plane net topology (4-c, uninodal net). The luminescence studies affirm that the emissions from MOFs owing to π-electron rich ligand establish charge transfer transitions (n–π* and π–π*). MOF-AA has attractive luminescent property, and exhibits distinguished applications for the selective as well as sensitive detection of 4-nitrophenol.

Transmit power optimisation in cellular networks with nomadic base stations

The increasing demand for cellular network capacity can be mitigated through the installation of nomadic eNodeB, which serve a temporal increase of traffic volume in specific area. When nomadic cells are deployed, the transmission power of neighbour base stations needs to be optimised to limit the inter-cell interferences. The authors analyse the problem of neighbourhood selection for the optimisation, to define what part of the networks needs to be reconfigured when new base station is added. They evaluate the iterative approach, with increasing range of neighbouring cells being reconfigured and propose a novel, sampling-based local TX power reconfiguration method, which is evaluated by a numerical model in both regular (honeycomb) topology and in realistic topology reflecting locations of cells in a city. The analysis confirms that the proposed algorithm allows to select small subset of neighbouring cells to be reconfigured (in majority of the cases < 10 cells), and achieve similar efficacy as global optimisation, with total network throughput different by < 1 % comparing to the global optimisation.

A method of failure modeling for 3D printed cellular structures

The paper presents a new approach for failure modeling of a cellular structure manufactured with a 3D printing technology. For this purpose, the honeycomb topology was designed and fabricated using fused deposition modeling of ABSplus material. The proposed method was based on the tiebreak contact for connecting plastic joints with cell walls. Additionally, two methods based on constitutive models were also analyzed. In the first case, an elasto-plastic material model was adopted, whereas in the second case an elasto-visco-plastic material model with damage was included. Firstly, the mechanical properties of ABSplus material were determined and numerically correlated with experimental outcomes. Subsequently, a contact parametric study was performed, and the optimal contact parameters were evaluated. The quasi-static experimental compression tests were simulated using LS-Dyna software. The results of actual tests and numerical analyses with three different methods for honeycomb structure modeling were compared in terms of deformation, force history, failure behavior and energy absorption capabilities. It was shown that the contact-based method resulted an in an increase of the results quality with better reproduction of force characteristic and progressive failure behavior during the deformation process, compared to other two methods.

Static and Dynamic Loading Behavior of Ti6Al4V Honeycomb Structures Manufactured by Laser Engineered Net Shaping (LENSTM) Technology.

Laser Engineered Net Shaping (LENSTM) is currently a promising and developing technique. It allows for shortening the time between the design stage and the manufacturing process. LENS is an alternative to classic metal manufacturing methods, such as casting and plastic working. Moreover, it enables the production of finished spatial structures using different types of metallic powders as starting materials. Using this technology, thin-walled honeycomb structures with four different cell sizes were obtained. The technological parameters of the manufacturing process were selected experimentally, and the initial powder was a spherical Ti6Al4V powder with a particle size of 45–105 µm. The dimensions of the specimens were approximately 40 × 40 × 10 mm, and the wall thickness was approximately 0.7 mm. The geometrical quality and the surface roughness of the manufactured structures were investigated. Due to the high cooling rates occurring during the LENS process, the microstructure for this alloy consists only of the martensitic α’ phase. In order to increase the mechanical parameters, it was necessary to apply post processing heat treatment leading to the creation of a two-phase α + β structure. The main aim of this investigation was to study the energy absorption of additively manufactured regular cellular structures with a honeycomb topology under static and dynamic loading conditions.

Relations between Structural and Luminescence Properties of Novel Lanthanide Nitrate Complexes with Bis-phosphoramidate Ligands.

Five new bisphosphoramide-based LnIII nitrate complexes [La2(NO3)6L3I] n (1), [Ce2(NO3)6L3I] n (2), [Sm2(NO3)6L3II] n (3), Sm2(NO3)6L3III (4), and Er(NO3)3L2III (5) [LI = piperazine-1,4-diylbis(diphenyl phosphine oxide), LII = N, N'-(ethane-1,2-diyl)bis( N-methyl- P, P-diphenylphosphinic amide, and LIII = N, N'-(ethane-1,2-diyl)bis( P, P-diphenylphosphinic amide)] have been synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), and single crystal X-ray and powder diffractions. The results of the X-ray diffraction analysis revealed the new polymorph of LIII, and the structural diversity of the synthesized complexes in the solid state. Complexes 1-3 display two-dimensional coordination polymers (2D-CP), containing layers with honeycomb (6, 3) topology. In these 2D-CPs, each Ln center (La, Ce, and Sm in 1, 2, and 3, respectively) could be considered as a triconnected node, linked by three bridging bisphosphoramide ligands as two-connecting linkers. In contrast, 4 is a discrete binuclear complex, in which bidentate LIII ligand has two entirely different conformations: the syn chelating and the anti bridging. Cationic complex 5 shows the monomeric structure, where bidentate LIII adopts the syn-chelating conformation. A comprehensive luminescence investigation has been performed on free ligands and their corresponding complexes as well. The synthesized compounds display a variety of luminescence behavior, including the ligand-centered fluorescence in 1, 2, and 5, two distinct emission peaks in 1 and 2, characteristic Sm-centered f-f emission in 3 and 4, and excitation-dependent emission in LIII, 1, and 2. Furthermore, the time-dependent density functional theory (TD-DFT) study was carried out on the reported compounds to understand the nature of the emission peaks and the observed luminescence properties. The solid-state emission quantum yields of lanthanide complexes were also determined at different excitation wavelengths.

H2WNoC: A honeycomb hardware-efficient wireless network-on-chip architecture

Network-on-chips (NoCs) have emerged as communication backbones for enabling massive parallelism and high degree of integration in many-core chips. In spite of the advantages of conventional NoCs, wired multi-hop links impose limitations on NoCs performance by long delay and high power consumption especially in large systems. To alleviate these problems, different solutions such as wireless network-on-chip (WiNoC) designs have been proposed. WiNoCs benefit from long-range, high bandwidth and low power wireless links to solve problems corresponding to wired communications. Most of the WiNoC architectures have been designed based on mesh topology, while, honeycomb topology provides more energy-efficient NoC architecture with higher throughput than mesh topology, but, as we will show, a honeycomb-based WiNoC, by itself, does not reduce the amount of utilized hardware resources and delay. In this paper, we propose a hardware-efficient WiNoC with honeycomb topology, namely, H2WNoC aiming at reducing hardware resources, network cost, delay, and also energy consumption. Considering different performance parameters, cycle-accurate-based evaluations are performed for the proposed architecture; H2WNoC is compared with the traditional mesh WiNoC, as the baseline, and also with three state-of-the-art WiNoC architectures. Furthermore, design space exploration of the proposed architecture is performed. Performance evaluations indicate that H2WNoC utilizes less hardware resources, consumes less amount of energy and improves both throughput and delay, compared to the other WiNoC architectures. Moreover, the obtained results show that the proposed architecture outperforms wired NoCs either with mesh or honeycomb topology.

A honeycomb-layered 2D coordination polymer of [Pb(TMA)]n (H2TMA = 3‑thiophenemalonic acid) for impedimetric humidity sensing with high performance

A novel lead-based two-dimensional (2D) coordination polymer of [Pb(TMA)]n (named as PbL, H2TMA = 3-thiophenemalonic acid) was synthesized via a facile precipitation method at room temperature. The PbL shows a 6, 3-connected network of honeycomb topology with thiophene rings on each side of the layer. It is worth noting that unusual PbS weak bonds (3.39 Å) further link the honeycomb layers to generate a three-dimensional (3D) supramolecular framework. Taking inspiration from the 2D lamellar structure and abundant active sites (such as Pb2+ ions, O and S atoms), which will facilitate the adsorption and interaction of water molecules on PbL surface, an impedimetric humidity sensor was fabricated based on this framework. The PbL sensor exhibited high response, good repeatability, small hysteresis, as well as short response and recovery times. Finally, the humidity sensing mechanism of this PbL sensor has been discussed through complex impedance analysis, confirming the contributions of distinct charge carriers at different relative humidity (RH). This work provides a practical candidate for humidity sensors and further develops a new promising application for coordination polymers in electrical sensory devices.

Deformation of honeycomb cellular structures manufactured with Laser Engineered Net Shaping (LENS) technology under quasi-static loading: Experimental testing and simulation

The paper presents a methodology investigation of honeycomb cellular structures deformation process in quasi-static compression tests. Two honeycomb topologies with different elementary cells were designed and manufactured from Ti-6Al-4 V alloy powder with the use of Laser Engineered Net Shaping (LENS) system and compressed using a universal strength machine. To simulate the deformation process with LS-Dyna software, the mechanical properties of the material were assessed and correlated. An elasto-visco-plastic material model (Mat_Plasticity_With_Damage) was used for predicting the material behavior. The results of experimental tests and numerical simulations were compared. A reasonable agreement between deformation, failure and force histories was obtained. Additionally, both the topologies were compared for their energy absorption capabilities. The validated numerical modelling with the adopted constitutive model will be used in the further studies to analyze different cellular structures topologies subjected to dynamic loading.

Emerging many-body effects in semiconductor artificial graphene with low disorder

The interplay between electron–electron interactions and the honeycomb topology is expected to produce exotic quantum phenomena and find applications in advanced devices. Semiconductor-based artificial graphene (AG) is an ideal system for these studies that combines high-mobility electron gases with AG topology. However, to date, low-disorder conditions that reveal the interplay of electron–electron interaction with AG symmetry have not been achieved. Here, we report the creation of low-disorder AG that preserves the near-perfection of the pristine electron layer by fabricating small period triangular antidot lattices on high-quality quantum wells. Resonant inelastic light scattering spectra show collective spin-exciton modes at the M-point's nearly flatband saddle-point singularity in the density of states. The observed Coulomb exchange interaction energies are comparable to the gap of Dirac bands at the M-point, demonstrating interplay between quasiparticle interactions and the AG potential. The saddle-point exciton energies are in the terahertz range, making low-disorder AG suitable for contemporary optoelectronic applications.

Ocena jakościowa procesu deformacji regularnych struktur komórkowych wykonanych techniką druku 3D

Presented are selected experimental results concerning the analysis of the deformation process of regular cellular structures manufactured using 3D printing under quasi-static loading conditions. The various structural topologies were designed and manufactured using the FDM (fused deposition modelling) and then tested in a uniaxial compression test. The starting point for the development of individual variants of structures was the honeycomb topology. In order to analyse the influence of the structure material on the deformation process, the samples were made from three commercially available materials: PC-10, ABSplus and Nylon12. Based on the results, the influence of the shape of the single cell and the type of material used on the deformation of the structure as well as the value of the plastic deformation energy were assessed.

Structural Consequences of 1,4-Cyclohexanedicarboxylate Cis/Trans Isomerism in Uranyl Ion Complexes: From Molecular Species to 2D and 3D Entangled Nets.

trans-1,4-Cyclohexanedicarboxylic acid (t-1,4-chdcH2) or the commercially available mixture of the cis and trans isomers (c,t-1,4-chdcH2) has been used in the synthesis of a series of 14 uranyl ion complexes, all obtained under solvohydrothermal conditions, some in the presence of additional metal cations and/or 2,2'-bipyridine (bipy). With its two isomeric forms having very different shapes and its great sensitivity to the experimental conditions, 1,4-chdc2- appears to be suitable for the synthesis of uranyl ion complexes displaying a wide range of architectures. Under the conditions used, the pure trans isomer gives only the complexes [UO2(t-1,4-chdc)(H2O)2] (1) and [UO2(t-1,4-chdc)] (2), which crystallize as one- and two-dimensional (1D and 2D) species, respectively. Complexes containing either the cis isomer alone or mixtures of the two isomers in varying proportion were obtained from the isomer mixture. The neutral complexes [UO2(c-1,4-chdc)(DMF)] (3) and [UO2(c-1,4-chdc)(bipy)] (4) are 2D and 1D assemblies, respectively, while all the other complexes are anionic and include various counterions. [C(NH2)3]3[H2NMe2][(UO2)4(c-1,4-chdc)6]·H2O (5) crystallizes as a three-dimensional (3D) framework with {103} topology. While [H2NMe2]2[(UO2)2(c-1,4-chdc)2(t-1,4-chdc)]·DMF·2H2O (6) is a 1D ladderlike polymer, [H2NMe2]2[(UO2)2(c-1,4-chdc)(t-1,4-chdc)2]·2H2O (7), which differs in the cis/trans ratio, is a 3-fold 2D interpenetrated network with {63} honeycomb topology. The related [H2NMe2]2[(UO2)2(c,t-1,4-chdc)3]·2.5H2O (8), with one disordered ligand of uncertain geometry, is a 3-fold 3D interpenetrated system. The two isomorphous complexes [Co(bipy)3][(UO2)2(c-1,4-chdc)3]·1.5H2O (9) and [Cd(bipy)3][(UO2)2(c-1,4-chdc)3]·1.5H2O (10) form 3D frameworks with the {103} srs topological type. In contrast, [Ni(bipy)3]2[(UO2)4(c-1,4-chdc)2(t-1,4-chdc)(NO3)6]·2H2O (11) is a molecular, tetranuclear complex due to the presence of terminal nitrate ligands. A 2-fold 3D interpenetration of frameworks with {103} ths topology is observed in [Cu(bipy)2]2[(UO2)2(c-1,4-chdc)2(t-1,4-chdc)]·2H2O (12), while [Zn(bipy)3][(UO2)2(c-1,4-chdc)3]·4H2O (13) crystallizes as a 2D net with the common {4.82} fes topological type. The additional PbII cation is an essential part of the 3D framework formed in [UO2Pb2(c-1,4-chdc)(t-1,4-chdc)2(bipy)2] (14), in which uranyl and its ligands alone form 1D subunits. Together with previous results, the solid-state uranyl emission properties of seven of the present complexes evidence a general trend, with the maxima for the complexes with O6 equatorial environments being blue-shifted with respect to those for complexes with O5 environments.

Honeycomb Boron Allotropes with Dirac Cones: A True Analogue to Graphene.

We propose a series of planar boron allotropes with honeycomb topology and demonstrate that their band structures exhibit Dirac cones at the K point, the same as graphene. In particular, the Dirac point of one honeycomb boron sheet locates precisely on the Fermi level, rendering it as a topologically equivalent material to graphene. Its Fermi velocity (vf) is 6.05 × 105 m/s, close to that of graphene. Although the freestanding honeycomb B allotropes are higher in energy than α-sheet, our calculations show that a metal substrate can greatly stabilize these new allotropes. They are actually more stable than α-sheet sheet on the Ag(111) surface. Furthermore, we find that the honeycomb borons form low-energy nanoribbons that may open gaps or exhibit strong ferromagnetism at the two edges in contrast to the antiferromagnetic coupling of the graphene nanoribbon edges.

Bending behavior of sandwich composite structures with tunable 3D-printed core materials

We combine 3D printing technique, numerical analysis, and experiments to design a new class of sandwich composites that exhibit various bending behaviors. These programmed sandwich structures contain 3D printed core materials with truss, conventional honeycomb, and re-entrant honeycomb topologies. Three-point bending tests are performed to investigate the bending behavior of these sandwich composites with two types of carbon fiber reinforced polymer face sheets. Under bending deformation, sandwich composites with truss core materials provide highest flexural stiffness and strength that are desirable in structural components. The sandwich composites with re-entrant honeycomb core exhibit a sequential snap-through instability which significantly enhances the energy absorption abilities. Our experimental and numerical results indicate that architected core structures can be utilized to tailor the bending properties as well as failure mechanisms. These findings offer new insights into the study of nonlinear mechanical response of sandwich structures, which can benefit a wide range of industries and applications.

On the dynamic compression of cellular materials with local structural softening

Analytical and numerical analyses are carried out in order to reveal the importance of the cellular materials topology for their dynamic compaction. The aim is to distinguish between the deformation and energy absorption mechanisms of materials which exhibit local structural softening, such as out-of-plane loaded honeycomb, and materials with local structural hardening (foam). It is shown that the dynamic out-of-plane compaction of honeycombs does not obey the law of shock wave propagation and a new phenomenological model of the velocity attenuation is proposed. It is revealed that the absorbed energy by the honeycomb is proportional to the area under the dynamic stress-strain curve, which is defined by the foil material properties, in contrast to the shock-wave propagation model where the absorbed energy is proportional to the area under the shock chord. Comparisons with the predictions of the Rigid Perfectly-Plastic Locking (RPPL) model, which approximates well the average quasi-static stress-strain characteristic of a honeycomb, are discussed. Special attention is given to the effects of neglecting the honeycomb topology on their response to impact loading.Finite element simulations are carried out to verify the proposed theoretical model revealing the major factors which influence the dynamic response of out-of-plane loaded honeycombs to high velocity impact.

Two-dimensional honeycomb (A7) and zigzag sheet (ZS) type nitrogen monolayers. A first principles study of structural, electronic, spectral, and mechanical properties

Two single-bonded 2D nitrogen allotropes of the honeycomb (A7) and zigzag sheet (ZS) topology have been calculated using density functional theory (DFT). The optical (vibrational, absorption, nuclear magnetic resonance), thermodynamic and elastic properties of the A7 and ZS sheets have been calculated for the first time. The band structure calculation have revealed a semiconducting nature of the ZS sheet with a direct gap of 1.246eV, while the A7 monolayer behaves as an insulator with an indirect gap of 3.842eV. Phonon dispersion calculations have justified these structures as vibrationally stable 2D materials. The IR spectroscopy completely failed in the characterization of the studied materials, while the Raman spectroscopy can be effectively applied for the experimental spectral identification. The absorption spectra demonstrate complete opacity of the A7 and ZS monolayers to the UV irradiation only above ca. 9 and 6eV, respectively. Thus, the studied materials are expected to be transparent to the visible light. The electron arrangement of the nitrogen nuclei in the studied polynitrogen sheets is denser compared to the N2 molecule which follows from the calculation of the values of magnetic shielding tensors. The elastic constants reveal a robust mechanical stability of the studied 2D nitrogen allotropes. The Young moduli values are only twice as lower than that of the graphene molecule.

Computation of the homogenized nonlinear elastic response of 2D and 3D auxetic structures based on micropolar continuum models

We develop mechanical and numerical homogenization models for the large strains response of auxetic structures in order to derive their effective elastic response accounting for large changes of the geometry. We construct a strain driven nonlinear scheme for the computation of the stress-strain relation of these repetitive networks over a reference representative unit cell (abbreviated as RUC). Homogenization schemes are developed to evaluate the effective nonlinear mechanical response of periodic networks prone to an auxetic behavior, in both planar and 3D configurations, which are substituted by an effective micropolar continuum at the intermediate mesoscopic level. The couple stress part of the homogenized constitutive law takes into account the impact of the local rotations at the mesoscopic level and allows computing the bending response. This methodology is applied to four planar auxetic periodic lattices (the re-entrant hexagonal honeycomb and alternative honeycomb topologies, including the arrowhead, Milton and hexachiral structures), and to the 3D re-entrant and pyramid-shaped lattices. We have considering successively the in-plane and out-of-plane responses of these structures. The transition to an auxetic behavior is shown to be triggered by the imposed strain over the unit cell boundary. The computed evolutions of Poisson’s ratio versus the imposed stretch traduce an enhanced auxetic response as the stretch is increased. A satisfactory agreement is obtained between the homogenized stress-strain responses and the responses computed numerically by finite element simulations performed over a repeating unit cell.

Variations on the Honeycomb Topology: From Triangular- and Square-Grooved Networks to Tubular Assemblies in Uranyl Tricarballylate Complexes

Depending on the counterion, uranyl tricarballylate, UO2(tca)−, is shown to crystallize either as two-dimensional nets or as one-dimensional tubules, all with honeycomb topology and united into higher dimensional assemblies when additional metal cations (AgI, PbII) are present. A regular geometric progression involving ligand reorientation is apparent in the series, with triangular furrows in [H2NMe2][UO2(tca)]·H2O (1) followed by deepening square grooves in [UO2Ag(tca)(H2O)]·0.5H2O (2) and full closure of square tubules in [NH4][(UO2)2Pb(tca)2(NO3)(bipy)].