纳米金-蛋白A介导抗体定向固定的压电传感及电化学特性研究

以纳米金为载体标记蛋白A(PA),用于介导抗体在压电石英晶体金电极表面的定向固定化.以补体C_1q抗体为模型,采用压电传感技术实时监察了此敏感界面的免疫反应过程,并考察了与补体C_1q免疫反应的压电响应性能.金标PA固定抗体的方法与传统的直接PA固定化方法相比较,具有传感界面无需活化,固定抗体的免疫活性高等优点,可对相应抗原进行高灵敏的压电免疫检测.分别利用循环伏安和电化学交流阻抗技术对金标PA固定抗体及其免疫反应的动力学过程进行了表征.     

Design and Performance of a New Thin‐Layer Radial‐Flow Holder for a Quartz Crystal Resonator of an Electrochemical Quartz Crystal Microbalance

A new compact holder for either 5‐ or 10‐MHz AT‐cut quartz crystal resonator of an electrochemical quartz crystal microbalance was designed, fabricated and characterized. The holder is a hydrodynamically controlled thin‐layer radial‐flow microelectrochemical cell. Its unique feature consists of (i) a micrometer‐screw adjustable distance between the movable coaxial assembly of the Ag/Ag⁺ pseudoreference electrode and the inlet capillary nozzle with respect to the metal‐film working electrode of the quartz crystal resonator, and (ii) a U‐clamp mountable resonator, easily accessible for change without using any tools. The inlet solution stream is centered axially against the working electrode. The holder performance was tested under different flow conditions. These include hydrodynamic voltammetry measurements on the Fe(CN) /Fe(CN) couple, i.e., a redox system with no mass transfer across the solution–electrode interface, as well as simultaneous chronoamperometry and chronoelectrogravimetry measurements under flow injection analysis (FIA) conditions on the Ag/Ag⁺ couple, i.e., a system with electrodeposition of a rigid metallic film. Moreover, simultaneous changes of resonant frequency and dynamic resistance were measured under FIA conditions for a glycerol solution, i.e., an electroinactive viscous medium. For the 30<F_m<180 μL min^?1 volume flow rate of solution and 50<d<250 μm nozzle‐to‐resonator distance, the holder operates in a thin‐layer radial‐flow regime at a fully developed laminar flow. For F_m=30 μL min^?1 and d=100 μm, both mass and charge conversion accompanying silver electrodeposition is appreciably high and close to 35%. Simultaneous measurements of the resonant frequency change and current‐potential or current‐time transients allowed investigations of electrochemical processes involving mass changes of rigid deposits while those of the frequency change and dynamic resistance change involve changes of viscoelastic properties of medium.     

Kinetic calculations of the Ni anodic dissolution from EIS

Anodic nickel dissolution in acid media has been analyzed by means of electrochemical quartz crystal microbalance and electrochemical impedance spectroscopy techniques. The experimental impedance spectra have been fitted to an equivalent circuit which is related to a mechanism of two consecutive electron transfers followed by a Ni²⁺ mass transfer step. That way, an estimation for values of rate constants and surface concentrations of the Ni(0), Ni(I) and Ni(II) species has been obtained.     

Formation and redox behaviour of polycarbazole prepared by electropolymerization of solid carbazole crystals immobilized on an electrode surface

Carbazole solid crystals have been mechanically attached to platinum or gold electrodes by two different methods and investigated by cyclic electrochemical quartz crystal microbalance measurements in the presence of aqueous acidic media. It was demonstrated that oxidative dimerization and polymerization can also be accomplished under such conditions. During electropolymerization, anions and water molecules enter the surface layer; however, these species leave the film after the reduction of the polymer formed. The mass changes observed in the course of the redox transformations of polycarbazole film can be explained by potential- and time-dependent sorption/desorption of H⁺ and ClO₄ ⁻ ions. The electroactivity of the polymer diminishes in more dilute acid media; however, it is recovered again in concentrated HClO₄ solutions. In more dilute acid solution the extent of the water sorption (film swelling) increases.     

Multi-wall carbon nanotubes (MWCNTs)-doped polypyrrole DNA biosensor for label-free detection of genetically modified organisms by QCM and EIS

In this paper, we describe DNA electrochemical detection for genetically modified organism (GMO) based on multi-wall carbon nanotubes (MWCNTs)-doped polypyrrole (PPy). DNA hybridization is studied by quartz crystal microbalance (QCM) and electrochemical impedance spectroscopy (EIS). An increase in DNA complementary target concentration results in a decrease in the faradic charge transfer resistance (R_ct) and signifying “signal-on” behavior of MWCNTs-PPy-DNA system. QCM and EIS data indicated that the electroanalytical MWCNTs-PPy films were highly sensitive (as low as 4 pM of target can be detected with QCM technique). In principle, this system can be suitable not only for DNA but also for protein biosensor construction.     

Comparative Permeation Study of Different Types of Myoglobin Layer‐by‐Layer Films and the Effect of Film Permeability on Their Electrochemistry and Electrocatalysis

Three different types of myoglobin (Mb) layer‐by‐layer films were assembled respectively with TiO₂ sol‐gel by vapor‐surface deposition, TiO₂ nanoparticles, and poly(styrenesulfonate), designated as {SG‐TiO₂/Mb}_n, {NP‐TiO₂/Mb}_n, and {PSS/Mb}_n. The permeability of the films was studied and compared by rotating disk voltammetry (RDV) and electrochemical impedance spectroscopy (EIS) with different electroactive probes, showing a general permeability sequence of {SG‐TiO₂/Mb}_n>{NP‐TiO₂/Mb}_n>{PSS/Mb}_n. The electrochemical and electrocatalytic activity of Mb in these films were also investigated and compared by cyclic voltammetry (CV), RDV, and amperometry, indicating that among the three Mb films, {SG‐TiO₂/Mb}_n films demonstrated the highest maximum surface concentration of electroactive Mb and the best electrocatalytic performances toward reduction of H₂O₂. All these advantages could be attributed to the unique architecture and porous structure of {SG‐TiO₂/Mb}_n films, which could greatly facilitate the mass transport of small counterions and catalytic substrates within the films. The various influencing factors on the permeability, electrochemistry, and electrocatalysis of the Mb films were also investigated in detail.     

Voltammetry of Undiluted Red‐Ox Systems. Electrochemical ESR‐ and Electrochemical Impedance Spectroscopy Evidence for Formation of Ionic Liquid at Microelectrode Surface

It is believed that voltammetry of undiluted red‐ox liquids can lead to the formation of stable thin layers of ionic liquids at the microelectrode surface. Such situation was postulated for several liquids (solvents), however, so far no hard evidence supporting this expectation was obtained. By using electron spin resonance in combination with voltammetric experiments and electrochemical impedance spectroscopy we have shown that the concentration of the cation radicals at the microelectrode surface may be high (nitrobenzene) and the overall resistance of the solution abruptly drops (methanol) when the potential at the microelectrode corresponds to the wave plateau of the undiluted organic liquid. Both facts constitute a good evidence for the formation of microlayers of ionic liquids at the microelectrode surface during electrolysis of undiluted red‐ox systems.     

Polycrystalline Gold Electrodes: A Comparative Study of Pretreatment Procedures Used for Cleaning and Thiol Self‐Assembly Monolayer Formation

The influence of different surface pretreatment procedures on the electrochemical response of a polycrystalline gold electrode was evaluated. Mechanical polishing with slurry alumina (M), chemical oxidation with H₂SO₄/H₂O₂ (C), electrochemical polishing (potential cycling between ?0.1 V and 1.2 V vs. SCE) (E), chemical reduction with ethanol, and combinations among these treatments were employed to change the surface electrode characteristics. The efficiency of the proposed pretreatments was evaluated by electrochemical responses towards the redox couple ferri(II/III)‐ammonium sulfate and by the formation of a self‐assembly monolayer of 3‐mercaptopropionic acid (3 MPA SAM) on gold electrodes. The procedure (C) allowed important gold surfaces activation. Using procedures (C) and (E) the roughness of polycrystalline gold surfaces was significantly minimized and more reproducible surfaces could be obtained. From the profile of reductive desorption of 3 MPA SAM it was possible to verify that reduced gold surfaces generated better packed monolayers than oxidized ones and a comparative study using CV and DPV techniques showed that between the two desorption peaks, the one localized at more negative potential values corresponds to the cleavage of Au‐S bond from the chemisorbed thiol. In general, the improvement in the studied electrochemical responses could not only be attributed to an increase in the real surface area of the electrode, but to the chemical surface states set off by the pretreatment procedure.     

Electrochemical Characterization of Gold 6‐Amino‐2‐mercaptobenzothiazole Self‐Assembled Monolayer for Dopamine Detection in Pharmaceutical Samples

A new sensor, gold‐6‐amino‐2‐mercaptobenzothiazole (6A2MBT), was fabricated via a self‐assembly procedure. Electrochemical properties of the monolayer were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The modified electrode showed excellent antifouling property against the oxidation products of DA, allowed us to construct a dynamic calibration curve with two linear parts, 1.00×10^?6 to 3.72×10^?4 and 3.72×10^?4 to 6.42×10^?4 M DA, with correlation coefficients of 0.997 and 0.992 and a detection limit of 1.57×10^?7 M DA by using differential pulse voltammetry (DPV), respectively. Finally, the performance of the Au‐6A2MBT modified electrode was successfully tested for electrochemical detection of DA in a pharmaceutical sample.     

Piezoelectric Crystal Liquid Flow Detection Systems Based on Alkyl (C18)‐Benzo‐15‐Crown 5 for Organic Compounds and Metal Ions

A water in soluble long‐chain crown ether alkyl (C18)‐benzo‐15‐crown‐5 was synthesized and applied as a coating material on quartz crystal membranes of a liquid flow piezo electric crystal sensor. The oscillating crown ether‐coated piezo electric (PZ) crystal with a home‐made computer inter face was prepared as a liquid chromato graphic (LC) detector for organic species and metal ions in aqueous solutions. The oscillating frequency of the quartz crystal decreased due to the adsorption of organic molecules or metal ions on crown ether molecules. Effects of functional group, molar mass, steric hindrance, and polarity of organic molecules on frequency responses of the crown ether coated PZ crystal detector were investigated. The frequency responses of the crown ether coated PZ crystal detector for various molecules were in the order: amines > carboxylic acids > alcohols > ketones. The crown ether PZ detector also exhibited good sensitivity for some heavy metal ions and the frequency shifts were in the order: Cr³⁺ » Pb²⁺ > Co²⁺ > Cd²⁺ > Ni²⁺ > Cu²⁺. The crown ether coated piezo electric crystal LC detector demonstrated low detection limits for various polar organic molecules, e.g., 6.0 × 10^?5 M for propylamine, and metal ions, e.g., 2.9 × 10^?5 M (1.8 ppm) for Cu²⁺; the crown ether PZ detector also gave good reproducibility when re used. A quite sensitive electrochemical quartz crystal microbalance (EQCM) detection system was also set‐up for detecting trace heavy metal ions in solutions. The variation in frequency of the PZ crystal and the diffusion current were observed simultaneously after the reduction in heavy metal ions such as Cu²⁺ and Ni²⁺. The EQCM detection system exhibited fairly good sensitivity, e.g., 112 Hz/ppm for Cu²⁺ and a good detection limit, e.g., 0.13 ppm for Cu²⁺ ions. Comparison between EQCM and PZ detection systems was made and discussed.     

Biosensor Based on Self‐Assembling Glucose Oxidase and Dendrimer‐Encapsulated Pt Nanoparticles on Carbon Nanotubes for Glucose Detection

A novel amperometric glucose biosensor based on layer‐by‐layer (LbL) electrostatic adsorption of glucose oxidase (GOx) and dendrimer‐encapsulated Pt nanoparticles (Pt‐DENs) on multiwalled carbon nanotubes (CNTs) was described. Anionic GOx was immobilized on the negatively charged CNTs surface by alternatively assembling a cationic Pt‐DENs layer and an anionic GOx layer. Transmission electron microscopy images and ζ‐potentials proved the formation of layer‐by‐layer nanostructures on carboxyl‐functionalized CNTs. LbL technique provided a favorable microenvironment to keep the bioactivity of GOx and prevent enzyme molecule leakage. The excellent electrocatalytic activity of CNTs and Pt‐DENs toward H₂O₂ and special three‐dimensional structure of the enzyme electrode resulted in good characteristics such as a low detection limit of 2.5 μM, a wide linear range of 5 μM–0.65 mM, a short response time (within 5 s), and high sensitivity (30.64 μA mM^?1 cm^?2) and stability (80% remains after 30 days).     

Electrochemical Quartz Crystal Microbalance Studies on the Codeposition of Dextran Sodium Sulfate with the Charge‐Transfer Complexes Generated During Electrooxidation of Benzidine Derivatives

The electrochemical quartz crystal microbalance (EQCM) technique was used to investigate the electrochemistry of three benzidine derivatives, o‐tolidine (o‐TD), 3,3′,5,5′‐tetramethyl‐benzidine (TMB) and o‐dianisidine (o‐DA), in Britton‐Robinson (B‐R) buffer solutions with and without coexisting dextran sodium sulfate (DSS), respectively. During the anodic potential sweep from 0.1 to 0.7 V vs. SCE in pH 5.0 B‐R buffer solution containing o‐TD, the EQCM frequency was decreased during the first‐step oxidation of o‐TD and then increased to some extent during its second‐step oxidation, implying that a poorly soluble charge‐transfer complex (CTC) was produced here as an oxidation intermediate, and its precipitation and then dissolution at the EQCM Au electrode decreased and then increased the frequency. The depth of the V‐shaped time‐dependent frequency response (?Δf_0V) to the redox switching of the CTC/o‐TD couple (0.1–0.37 V vs. SCE) was notably enhanced in the presence of DSS, being due to the formation of a mass‐enhanced CTC‐DSS adduct via electrostatic affinity. Similar phenomena were evident in the TMB system, but the CTC behavior was not observed during o‐DA oxidation in the absence of DSS, namely, the EQCM frequency kept decreasing all the time, due probably to the too high lability of the CTC from o‐DA oxidation, and the coexistence of DSS could well stabilize this CTC and turn on its CTC behavior. The o‐TD system showed the highest sensitivity to DSS and was thus examined in detail. The mechanism for the CTC‐DSS interaction is discussed from EQCM, FT‐IR and UV‐vis data. The CTC‐based EQCM determination of DSS, which is featured by a dynamically renewed surface of the detection electrode, was thus proposed, with a linear range from 0.002 to 1.6 μmol L^?1 and a detection limit down to 0.7 nmol L^?1 (o‐TD system).     

EQCM and Fluoroelectrochemical Studies on the Catalytic Oxidation of NADH at a Pencil 8B‐Scrawled Gold Electrode with High Detection Sensitivity

We report for the first time the effective catalytic electrooxidation of nicotinamide adenine dinucleotide (NADH) on the pencil 8B‐scrawled gold electrode of an electrochemical quartz crystal microbalance (EQCM). The EQCM allowed us to quantitatively evaluate the catalytic activity of the pencil‐scrawled Au electrode. With increasing the mass of modified pencil powders, the peak potential for NADH oxidation shifted negatively, with maximum shift of ?0.35 V at saturated pencil modification; the NADH‐oxidation peak current density (j_p) was also notably increased, and the j_p at saturated pencil modification was found to be larger than those at conventional pencil 8B and bare Au electrodes. Sensitive amperometric detection of NADH was achieved at the gold electrode with saturated pencil modification, with low detection potential (0.4 V versus SCE), low detection limit (0.08 μmol L^?1) and wide linear range (0.2–710 μmol L^?1). The fluoroelectrochemical measurements of NADH at bare and pencil‐modified gold electrodes were also conducted with satisfactory results. The convenient and low‐cost modification of pencil powders on the Au electrode may have presented a new functional surface of the EQCM, which is recommended for wider applications to bioelectrochemical studies, especially in view of the EQCM's capability of providing abundant in situ information in relevant processes.     

Physical adsorption of protamine for heparin assay using a quartz crystal microbalance and electrochemical impedance spectroscopy

This study attempted to determine absolute heparin concentration in phosphate buffer solution (PBS, pH 7.4) by using quartz crystal microbalance (QCM) as an affinity biosensor. Electrochemical impedance spectroscopy (EIS) was also used to investigate immobilization of protamine and heparin assay. In addition, the effectiveness of physical adsorption in immobilizing protamine was confirmed by examining the preparation conditions, including the incubation time and protamine concentration. It induced maximum decrease (ca. −100 Hz) in oscillating frequency of QCM by applying 20 mg/ml protamine and 20 min for incubation in PBS. Heparin adsorption onto protamine-modified electrode in PBS revealed an exponential-like binding curve and long duration for reaching the steady state in frequency response of QCM. Moreover, two linear calibration curves were obtained judging from the initial slope (df/dt) and the frequency change (Δf) of QCM obtained after a binding interval (600 s) for heparin concentrations from 0 to 3.0 and 7.0 U/ml, respectively. In EIS analysis, calibration curves with linear concentration range of 0-3.0 U/ml were obtained for heparin in PBS when ferrocyanide was used as an electroactive marker.     

Specific Detection and Imaging of Enzyme Activity by Signal‐Amplifiable Self‐Assembling 19F MRI Probes

Specific turn‐on detection of enzyme activities is of fundamental importance in drug discovery research, as well as medical diagnostics. Although magnetic resonance imaging (MRI) is one of the most powerful techniques for noninvasive visualization of enzyme activity, both in vivo and ex vivo, promising strategies for imaging specific enzymes with high contrast have been very limited to date. We report herein a novel signal‐amplifiable self‐assembling ¹⁹F NMR/MRI probe for turn‐on detection and imaging of specific enzymatic activity. In NMR spectroscopy, these designed probes are “silent” when aggregated, but exhibit a disassembly driven turn‐on signal change upon cleavage of the substrate part by the catalytic enzyme. Using these ¹⁹F probes, nanomolar levels of two different target enzymes, nitroreductase (NTR) and matrix metalloproteinase (MMP), could be detected and visualized by ¹⁹F NMR spectroscopy and MRI. Furthermore, we have succeeded in imaging the activity of endogenously secreted MMP in cultured media of tumor cells by ¹⁹F MRI, depending on the cell lines and the cellular conditions. These results clearly demonstrate that our turn‐on ¹⁹F probes may serve as a screening platform for the activity of MMPs.     

Modification of Electrode Surfaces by Self‐Assembled Monolayers of Thiol‐Terminated Oligo(Phenyleneethynylene)s

The wire‐like properties of four S‐(4‐{2‐[4‐(2‐phenylethynyl)phenyl]ethynyl}phenyl) thioacetate derivatives, PhC≡CC₆H₄C≡CC₆H₄SAc ( 1 ), H₂NC₆H₄C≡CC₆H₄C≡CC₆H₄SAc ( 2 ), PhC≡CC₆H₂(OMe)₂C≡CC₆H₄SAc ( 3 ) and AcSC₆H₄C≡CC₆H₄C≡CC₆H₄SAc ( 4 ) (Figure 1 ), all of which possess a high degree of conjugation along the oligo(phenyleneethynylene) (OPE) backbone, were investigated as self‐assembled monolayers (SAMs) on gold and platinum electrodes by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The redox probe [Fe(CN)₆]₄^? was used in both the CV and impedance experiments. The results indicate that the thiolates derived from thioacetate‐protected precursor molecules 1 and 2 form well‐ordered monolayers on a gold electrode, whereas SAMs derived from 3 and 4 exhibit randomly distributed pinholes. The electron tunnelling resistance and fractional coverage of SAMs of all four compounds were examined using electron tunnelling theory. The analysis of the results reveal that the well‐ordered SAMs of 1 and 2 exhibit higher charge‐transfer resistance in comparison to the defect‐ridden SAMs of 3 and 4 . The additional steric bulk offered by the methoxy groups in 3 is likely to prevent efficient packing within the SAM, leading to a microelectrode behaviour, when assembled on a gold electrode surface. The protected dithiol derivative 4 probably binds to the surface through both terminal groups which prevents dense packing and leads to the formation of a monolayer with randomly distributed pinholes. Atomic force microscopy (AFM) was used to examine the morphology of the monolayers, and height images gave root‐mean‐square (RMS) roughness′s which are in agreement with the proposed SAM structures.     

Immobilization of atrazine on gold,a first step towards the elaboration of an indirect immunosensor: characterization by XPS and PM‐IRRAS

As part of our long‐term goal to design a novel type of immunosensor based on IR transduction, we devised two strategies to immobilize derivatives of the herbicide atrazine on the surface of planar gold substrates. Both strategies take advantage of the well‐known formation of self‐assembled monolayers of thiolates via spontaneous chemisorption of thiols or disulphides on noble metal surfaces. The first strategy involved the direct chemisorption of a disulphide derivative of atrazine, while the second strategy was based on the covalent attachment of a polymer tethered with atrazine derivatives to a previously adsorbed thiolate carrying a carboxylic acid head group. The resulting organic thin films on gold were characterized by polarization modulation infrared reflection‐absorption spectroscopy (PM‐IRRAS) and XPS. The binding of a polyclonal anti‐atrazine antibody to both sensing layers was also tested and compared. It appeared that specific molecular recognition occurred only on the atrazine disulphide sensing layer. Copyright © 2006 John Wiley & Sons, Ltd.     

Study on the Impedance Characteristic and Electrocatalytic Activity of Platinum‐Modified Polyaniline Film

The composite electrode of platinum‐modified polyaniline film is formed in 0.5 M H₂SO₄ + 3 mM H₂PtCl₆ solution by cyclic potential or constant potential deposition of platinum particles in polyaniline film. To make a comparison, the polyaniline film with the same initial thickness and structure is also treated with the cyclic potential or constant potential polarization in 0.5 M H₂SO₄ solution. The electrochemical impedance spectroscopy (EIS) of the composite electrode of platinum‐modified polyaniline film is studied in sulfuric acid solution and compared with the EIS of the polyaniline film without platinum dispersion. The results show that the different modes of potential polarization affect greatly the nature and distribution of the platinum particles, instead of the structure of the polyaniline film (matrix). The electrode reaction kinetics and mass transport process parameters involving charge transfer resistance (R_ct), double layer capacitance (C_dl), constant phase elements (CPE) and Warburg impedance in platinum substrate/platinum‐modified polyaniline film/solution interface are discussed on the basis of the interpretation of the characteristic impedance spectra and connected to the electrocatalytic activity on the oxidation of methanol molecules.     

Photocatalytic Nanocomposite Films Fabricated by Layer‐by‐Layer Self‐assembly of TiO2 Nanoparticles and Lignosulfonates

Photocatalytic multilayer nanocomposite films composed of anatase TiO₂ nanoparticles and lignosulfonates (LS) were fabricated on quartz slides by the layer‐by‐layer (LBL) self‐assembly technique. X‐ray photoelectron spectroscopy (XPS), UV‐vis spectroscopy and atomic force microscopy (AFM) were used to characterize the TiO₂/LS multilayer nanocomposite films. Moreover, the photocatalytic properties (decomposition of methyl orange and bacteria) of multilayer nanocomposite films were investigated. XPS results indicated that the intensities of titanium and sulfur peaks increased with the LBL deposition process. A linear increase in absorbance at 280 nm was found by UV‐Vis spectroscopy, suggesting that stepwise multilayer growth occurs on the substrate and this deposition process is highly reproducible. AFM images showed that quartz slide was completely covered by TiO₂ nanoparticles when a 10‐bilayer multilayer film was formed. The decomposition efficiency of methyl orange by TiO₂/LS multilayer films under the same UV irradiation time increased linearly with the number of TiO₂ layers, and the results of decomposition of bacteria under UV irradiation showed that TiO₂/LS multilayer nanocomposite films exhibited excellent decomposition activity of bacteria (Escherichia coil).     

Formation of a Hydrogen‐Bonded Heptazine Framework by Self‐Assembly of Melem into a Hexagonal Channel Structure

Self‐assembly of melem C₆N₇(NH₂)₃ in hot aqueous solution leads to the formation of hydrogen‐bonded, hexagonal rosettes of melem units surrounding infinite channels with a diameter of 8.9 Å. The channels are filled with strongly disordered water molecules, which are bound to the melem network through hydrogen bonds. Single‐crystals of melem hydrate C₆N₇(NH₂)₃ ? xH₂O (x≈2.3) were obtained by hydrothermal treatment of melem at 200 °C and the crystal structure (R $\bar 3$ c, a=2879.0(4), c=664.01(13) pm, V=4766.4(13)×10⁶ pm³, Z=18) was elucidated by single‐crystal X‐ray diffraction. With respect to the structural similarity to the well‐known adduct between melamine and cyanuric acid, the composition of the obtained product was further analyzed by solid‐state NMR spectroscopy. Hydrolysis of melem to cyameluric acid during syntheses at elevated temperatures could thus be ruled out. DTA/TG studies revealed that, during heating of melem hydrate, water molecules can be removed from the channels of the structure to a large extent. The solvent‐free framework is stable up to 430 °C without transforming into the denser structure of anhydrous melem. Dehydrated melem hydrate was further characterized by solid‐state NMR spectroscopy, powder X‐ray diffraction, and sorption measurements to investigate structural changes induced by the removal of water from the channels. During dehydration, the hexagonal, layered arrangement of melem units is maintained whereas the formation of additional hydrogen bonds between melem entities requires the stacking mode of hexagonal layers to be altered. It is assumed that layers are shifted perpendicular to the direction of the channels, thereby making them inaccessible for guest molecules.