IR spectroscopic studies of adsorption of dithiol-containing ligands on CdS nanocrystal films in aqueous solutions

The adsorption of the ligands alpha-lipoic acid, dihydrolipoic acid, and dithiothreitol to films of deposited CdS nanoparticles was studied in situ by ATR-IR spectroscopy. For alpha-lipoic acid and dihydrolipoic acid, the spectra of the adsorbed species closely resemble those of the respective solution species. However, for dithiothreitol, the spectrum of the adsorbed species is significantly different from that of the solution species and is attributed to an interruption of intermolecular hydrogen bonding upon adsorption to the CdS. The S-H stretching absorption of the dihydrolipoic acid solution species at pH=8.6 is observed at 2542 cm(-1). The corresponding absorptions for dithiothreitol occur at 2578 and 2528 cm(-1) and are attributed to monomers and dimers. Adsorption of dihydrolipoic acid and dithiothreitol is found to occur via both thiol functional groups and an additional interaction between the carboxylate and the CdS surface. The adsorption of alpha-lipoic acid to CdS in the presence of light proceeds with photo-oxidation of the CdS surface and reductive cleavage of the disulfide bond of alpha-lipoic acid to produce some adsorbed dihydrolipoic acid and thiosulfate. The adsorption of alpha-lipoic acid to CdS in the absence of visible light shows no photo-oxidation and suggests that adsorption occurs via retention of the disulfide bond. The adsorption isotherm data for dihydrolipoic acid and dithiothreitol gave good fits to the Langmuir isotherm, with adsorption constants higher than those for monothiol-containing ligands on CdS. The Langmuir adsorption constant for n-octanoic acid on CdS indicates that the additional interaction between the carboxylate group of dihydrolipoic acid and the CdS is weak in comparison with the dithiol interaction with CdS.     

Modeling the adsorption of citric acid onto Muloorina illite and related clay minerals

The adsorption of citric acid onto goethite, kaolinite, and illite was measured as a function of pH (adsorption edges) and concentration (adsorption isotherms) at 25 degrees C. The greatest adsorption was onto goethite and the least onto illite. Adsorption onto goethite was at a maximum below pH 5 and decreased as the pH was increased to pH 9. For kaolinite, maximum adsorption occurred between pH 4.5 and pH 7, decreasing below and above this pH region, while for illite maximum adsorption occurred between about pH 5 and pH 7, decreasing at both lower and higher pH. ATR-FTIR spectra of citrate adsorbed to goethite at pH 4.6, pH 7.0, and pH 8.8 were compared with those of citrate solutions between pH 3.5 and pH 9.1. While the spectra of adsorbed citrate resembled those of the fully deprotonated solution species, there were significant differences. In particular the C[bond]O symmetric stretching band of the adsorbed species at pH 4.6 and 7.0 changed shape and was shifted to higher wave number. Further spectral analysis suggested that citrate adsorbed as an inner-sphere complex at pH 4.6 and pH 7.0 with coordination to the surface most probably via one or more carboxyl groups. At pH 8.8 the intensity of the adsorbed bands was much smaller but their shape was similar to those from the deprotonated citrate solution species, suggesting outer-sphere adsorption. Insufficient citric acid adsorbed onto illite or kaolinite to provide spectroscopic information about the mode of adsorption onto these minerals. Data from adsorption experiments, and from potentiometric titrations of suspensions of the minerals in the presence of citric acid, were fitted by extended constant-capacitance surface complexation models. On the goethite surface a monodentate inner-sphere complex dominated adsorption below pH 7.9, with a bidentate outer-sphere complex required at higher pH values. On kaolinite, citric acid adsorption was modeled with a bidentate outer-sphere complex at low pH and a monodentate outer-sphere complex at higher pH. There is evidence of dissolution of kaolinite in the presence of citric acid. For illite two bidentate outer-sphere complexes provided a good fit to all data.     

Surface-enhanced Raman scattering and the adsorption behavior of (RS)-phenylsuccinic acid

The surface geometry of (RS)-phenylsuccinic acid molecule was studied by analysis of the SERS spectra of aromatic dicarboxylic acid adsorbed on silver colloid surfaces. For a reliable analysis of the SERS spectrum, we also performed density functional theoretical calculations. The SERS spectral features indicated that the RSPSA molecules should bound to the silver as dicarboxylate, with a strongly tilted orientation with respect to the normal to the surface. Such a tilted orientation was presumed to occur by the simultaneous sigma and pi-type coordination of carboxylate groups to silver surface caused by the steric hindrance and electrostatic repulsion between the two carboxylate groups, and thereby RSPSA on silver was easily displaced with aromatic carboxylic acids. A sigma-type coordination therefore seemed to be more important than a pi-type coordination for aromatic carboxylic acid derivatives to assemble on a silver surface. The large enhancement of in-plane bending, out of plane bending and ring breathing modes in the surface-enhanced Raman scattering spectrum indicates that the molecule is adsorbed on the silver surface in a 'at least vertical' configuration, with the ring perpendicular to the silver surface.     

In situ infrared spectroscopic analysis of the adsorption of aromatic carboxylic acids to TiO2, ZrO2, Al2O3, and Ta2O5 from aqueous solutions

In situ infrared spectroscopy has been used to investigate the adsorption of a range of simple aromatic carboxylic acids from aqueous solution to metal oxides. Thin films of TiO2, ZrO2, Al2O3 and Ta2O5 were prepared by evaporation of aqueous sols on single reflection ZnSe prisms. Benzoic acid adsorbed very strongly to ZrO2, in a bridging bidentate fashion, but showed only weak adsorption to TiO2 and Ta2O5. Substituted aromatic carboxylic acids; salicylic, phthalic and thiosalicylic, were found to adsorb to each metal oxide. Salicylic and phthalic acids adsorbed to the metal oxides via bidentate interactions, involving coordination through both carboxylate and substituent groups. Thiosalicylic acid adsorbed to the metal oxides as a bridging bidentate carboxylate with no coordination through the thiol substituent group.     

SiO2—Al2O3和MgO催化剂上吸附CH3NO2的TPD和IR研究

用TPD和IR方法研究了CH_3NO_2在典型固体酸SiO_2-Al_2O_3和固体碱MgO催化剂上的吸附分解。结果表明,在SiO_2-Al_2O_3表面CH_3NO_2吸附转化为表面甲酰胺物种,后者在高温下分解为CO_2和NH_3。在MgO表面CH_3NO_2吸附形成多种表面化学物种,它们在升温过程中脱附,并通过表面亚硝基甲烷物种分解为NO、C_2H_4、C_2H_6和N_2O.讨论了CH_3NO_2分解过程中表面酸、碱中心的作用。     

Comparison of complexed species of Eu in alumina-bound and free polyacrylic acid: a spectroscopic study

The speciation of Eu complexed with polyacrylic acid (PAA) and alumina-bound PAA (PAA(ads)) was studied at pH 5 in 0.1 M NaClO(4). Structural parameters were obtained from (7)F(0) -->(5)D(0) excitation spectra measured by laser-induced fluorescence spectroscopy as well as from Eu L(III)-edge extended X-ray absorption fine structure (EXAFS) spectra. The coordination mode was also investigated by infrared spectroscopy. To elucidate the nature of the complexed species, Eu-acetate complexes were used as references. The spectroscopic techniques show that two carboxylate groups with 2-3 (EuPAA) and 4-5 (EuPAA(ads)) water molecules are coordinated to Eu in the first coordination sphere. For EuPAA(ads), the coordination between carboxylate groups and Eu appears to be bidendate. A similar coordination is probable for EuPAA but the EXAFS data indicate a slightly distorted coordination. The results show that the degree of freedom of carboxylate groups is not the same for free or adsorbed PAA. For PAA, the degree of freedom is constrained by the flexibility of the methylene chain. When PAA is adsorbed on alumina, the polymer chains cannot any more be treated as independent chains. One may rather assume formation of aggregates that form an organic layer at the mineral surface presenting a complex arrangement of carboxylate groups.     

From local adsorption stresses to chiral surfaces: (R,R)-tartaric acid on Ni(110).

The chiral molecule (R,R)-tartaric acid adsorbed on nickel surfaces creates highly enantioselective heterogeneous catalysts, but the nature of chiral modification remains unknown. Here, we report on the behavior of this chiral molecule with a defined Ni(110) surface. A combination of reflection absorption infrared spectroscopy, scanning tunneling microscopy, and periodic density functional theory calculations reveals a new mode of chiral induction. At room temperatures and low coverages, (R,R)-tartaric acid is adsorbed in its bitartrate form with two-point bonding to the surface via both carboxylate groups. The molecule is preferentially located above the 4-fold hollow site with each carboxylate functionality adsorbed at the short bridge site via O atoms placed above adjacent Ni atoms. However, repulsive interactions between the chiral OH groups of the molecule and the metal atoms lead to severely strained adsorption on the bulk-truncation Ni(110) surface. As a result, the most stable adsorption structure is one in which this adsorption-induced stress is alleviated by significant relaxation of surface metal atoms so that a long distance of 7.47 A between pairs of Ni atoms can be accommodated at the surface. Interestingly, this leads the bonding Ni atoms to describe a chiral footprint at the surface for which all local mirror symmetry planes are destroyed. Calculations show only one chiral footprint to be favored by the (R,R)-tartaric acid, with the mirror adsorption site being unstable by 6 kJ mol(-1). This energy difference is sufficient to enable the same local chiral reconstruction and motif to be sustained over 90% of the system, leading to an overall highly chiral metal surface.     

Functionalization of beta-Ga2O3 nanoribbons: a combined computational and infrared spectroscopic study

The adsorption of H 2O, alcohols (CH 3OH and 1-octanol), and carboxylic acids (formic, acetic, and pentanoic) on beta-Ga 2O 3 nanoribbons has been studied using infrared reflection-absorption spectroscopy (IRRAS) and/or ab initio computational modeling. Adsorption energies and geometries are sensitive to surface structure, and hydrogen bonding plays a significant role in stabilizing adsorbed species. On the more stable (100)-B surface, computation shows that the physisorption of H 2O or CH 3OH is weakly exothermic whereas chemisorption via O-H bond dissociation is weakly endothermic. Experiment finds that a large fraction of a saturation coverage of adsorbed 1-octanol is displaced by exposure to acetic acid vapor. This is consistent with computational results showing that acids adsorb more strongly than methanol on this surface. The remaining alcohol, not displaced by acetic acid, suggests the presence of defects and/or (100)-A regions because computation shows that this less-stable surface adsorbs methanol more strongly than does the (100)-B. The nu(C-H) modes of adsorbed 1-octanol are easily detected whereas no adsorbed H 2O is observed even though H 2O and CH 3OH exhibit similar adsorption energies. It is inferred from this that the failure to detect H 2O on the dominant (100)-B surface results from the orientation of the physisorbed H 2O essentially parallel to the surface. Computation shows that this configuration is stabilized by H bonding. For chemisorbed formic acid, computation shows that a bridging carboxylate structure is favored over a bidentate or monodentate configuration. Computation also shows that chemisorption is favored on the (100)-A surface but physisorption is favored on the more stable (100)-B. Analysis of IRRAS data for acetic and pentanoic acids finds evidence for both types of adsorption. The carboxylate resists displacement by H 2O vapor, which suggests that carboxylic acids may be useful for functionalizing beta-Ga 2O 3 surfaces. The results provide insight into the interplay between surface structure and reactivity on an oxide surface and about the importance of hydrogen bonding in determining adsorbate structure.     

Infrared study of the kinetics and mechanism of adsorption of acrylic polymers on alumina surfaces

In this paper, we studied the kinetics of the adsorption of poly(methyl methacrylate), PMMA, onto native aluminum oxide surfaces by X-ray photoelectron spectroscopy and reflection-absorption infrared spectroscopy, with the intent of tracking the various changes observed in the infrared spectrum of the adsorbed polymer layer as a function of adsorption time. Specifically, we utilized the relative changes in the absorption bands of the carbonyl, carboxylic acid, and carboxylate groups to determine the sequence of events that culminate in the formation of bonds between carboxylate groups on hydrolyzed PMMA and specific sites on the aluminum oxide surface. We have shown that the adsorption process involves the hydrolysis of a fraction of the methoxy groups of the PMMA to generate COOH groups. Unlike previous assumptions, the formation of COOH groups on the PMMA chains does not constitute a sufficient condition for the actual chemisorption of the polymer chains onto the metal oxide surface. To promote bonding, the acid groups must undergo dissociation to form the carboxylate groups, followed subsequently by actual bond formation, that is, active anchoring, on the surface. This process is mediated by the aluminum oxide sites on the surface in the presence of water. Hence, the adsorption process occurs via a two-step mechanism, in which the first step, that is, the hydrolysis step, is a necessary but insufficient condition and the second step, that is, the anchoring step, is largely dependent on the type of interfacial chemistry possible for a particular polymer-metal oxide surface, the polymer conformation, the molecular weight, and the flexibility of the adsorbing molecules.     

Adsorption of dicarboxylic acids on lithiated nickel oxide electrode

Adsorption of dicarboxylic acids on NiO electrodes was studied by means of the galvanostatic transient method, mainly for oxalic acid. The oxalate or hydrogen oxalate anion or both were concluded to adsorb on the electrode. The adsorption was maximal at a potential less positive than the flat-band potential of the electrode, owing to preferential adsorption of hydroxyl anion in the region above the maximum adsorption potential. The quantity of adsorption was dependent on carrier concentration of the electrode, and high for the electrode of high carrier concentration. This phenomenon is connected to the charged condition of the electrode that when the maximum adsorption takes place, positively charged sites remain on the surface of the electrode which is charged negatively as a whole and the amount of the sites is much more different between the electrodes of different N than their bulk carrier concentrations. Adsorptions of malonic and succinic acid were distinctly low compared with that of oxalic acid. The adsorbability was in the order; oxalic acid>malonic acid>succinic acid. This order was in accord with the stability constants of nickel dicarboxylic acid chelates.     

In-situ infrared study of the adsorption and oxidation of oxalic acid at single-crystal and thin-film gold electrodes: a combined external reflection infrared and ATR-SEIRAS approach

The adsorption and oxidation of oxalic acid at gold electrodes were studied by in-situ infrared spectroscopy. External reflection experiments carried out with gold single-crystal electrodes were combined with internal reflection (ATR-SEIRAS) experiments with gold thin-film electrodes. These gold thin films, with a typical thickness of ca. 35 nm, were deposited on silicon substrates by argon sputtering. As previously reported for evaporated gold films, the voltammetric curves obtained in sulfuric acid solutions after electrochemical annealing show typical features related to the presence of wide bidimensional (111) domains with long-range order. The in-situ infrared data collected for solutions of pH 1 confirmed the potential-dependent adsorption of either oxalate (Au(100)) or a mixture of bioxalate and oxalate (Au(111), Au(110), and gold thin films) anions in a bidentate configuration. The better signal-to-noise ratio associated with the SEIRA effect in the case of the gold thin-film electrodes allows the observation of the carbonyl band for adsorbed bioxalate that was not detected in the external reflection experiments. Besides, additional bands are observed between 2000 and 3000 cm(-)(1) that can be tentatively related to the formation of hydrogen bonds between neighboring bioxalate anions. The intensities of these bands decrease with increasing solution pH values, disappearing for pH 3 solutions in which adsorbed oxalate anions are the predominant species. The analysis of the intensities of the nu(s)(O-C-O) and nu(C-OH) + delta(C-O-H) bands for adsorbed oxalate and bioxalate, respectively, suggests that the pK(a) for the surface equilibrium between these species is significantly lower than that for the solution equilibrium.     

Effect of Formic Acid on the Outdiffusion of Ti Interstitials at TiO2 Surfaces: A DFT+U Investigation

Ti interstitials play a key role in the surface chemistry of TiO₂. However, because of their elusive behavior, proof of their participation in catalytic processes is difficult to obtain. Here, we used DFT+U calculations to investigate the interaction between formic acid (FA) and excess Ti atoms on the rutile-TiO₂(110) and anatase-TiO₂(101) surfaces. The excess Ti atoms favor FA dissociation, while decreasing the relative stability of the bidentate bridging coordination over the monodentate one. FA species interact significantly with the Ti interstitials, favoring their outdiffusion. Eventually, Ti atoms can emerge at the surface forming chelate species, which are more stable than monodentate FA species in the case of rutile, and are even energetically favored in the case of anatase. The presence of Ti adatoms that can directly participate to surface processes should then be considered when formic acid and possibly carboxylate-bearing species are adsorbed onto TiO₂ particles.     

Behavior of acid species during heat treatment and re-anodizing of porous alumina films formed in malonic acid

In the present work infrared spectroscopy, photoluminescence spectral measurements and the potenthiodynamic technique for studying the effect of treatment temperature on compositional and electronic properties of malonic acid alumina films were used. In the course of our studies, it has been proven that heat treatment of malonic acid films at temperatures from 250 up to 400 °C leads to considerable changes in the photoluminescence properties and voltammetric response during their potentiodynamic re-anodizing. We suggest that defects, such as electron traps, in this type of porous anodic films are caused by the atoms of hydrogen (one or two) escaping from the CH₂ groups of the malonic acid species as a result of the heat treatment. The sites of such defects provide pathways for easy electron migration under a high electric field increasing electroconductivity of anodic alumina films. On the contrary, no structural defects responsible for enhanced electroconductivity are observed during thermal splitting of oxalate groups in the oxalic acid alumina films.     

Density functional model studies of uranyl adsorption on (001) surfaces of kaolinite

The adsorption of uranyl on two types of neutral (001) surfaces of kaolinite, tetrahedral Si(t) and octahedral Al(o), was studied by means of density functional periodic slab model calculations. Various types of model surface complexes, adsorbed at different sites, were optimized and adsorption energies were estimated. As expected, the Si(t) surface was found to be less reactive than the Al(o) surface. At the neutral Al(o) surface, only adsorption at protonated sites is calculated to be exothermic for inner- as well as outer-sphere adsorption complexes, with monodentate coordination being preferred. Adsorption energies as well as structural features of the adsorption complexes are mainly determined by the number of deprotonated surface hydroxyl groups involved. Outer-sphere complexes on both surfaces exhibit a shorter U-O bond to the aqua ligand of uranyl that is in direct contact with the surface than to the other aqua ligands. This splitting of the shell of equatorial U-O bonds is at variance with common expectations for outer-sphere surface complexes of uranyl.     

Adsorption of ethoxylated cationic surfactants on self-assembled monolayers of alkanethiols on gold using surface plasmon resonance detection

Adsorption of a series of ethoxylated cationic surfactants at model surfaces of alkanethiol self-assembled monolayers was studied by the surface plasmon resonance technique. Model surfaces were tailor-made by choosing alkanethiols or mixtures of alkanethiols with methyl, hydroxyl, carboxyl, and trimethylammonium groups in terminal position. The ethoxylated and quaternized cationic surfactants having from 2 to 18 oxyethylene units, showed a decrease in adsorbed amount with increasing oxyethylene chain length for both hydrophobic and hydrophilic surfaces. On a negatively charged surface, containing carboxylate groups, the surfactant with only two oxyethylene groups adsorbed strongly due to electrostatic attraction and the adsorption increased with increasing amount of surface carboxylate groups. This work shows the usefulness of self-assembled alkanethiols on gold as a tool for performing surfactant adsorption studies on surfaces with variable hydrophobicity and charge.     

静态法和EXAFS技术研究Eu(III)在钛酸纳米管上的吸附行为和微观机制

结合静态实验和X射线吸收精细结构谱学(EXAFS)技术研究了pH、时间、有机配体等环境因素对放射性核素Eu(III)在钛酸纳米管上的吸附行为和微观机制的影响.宏观实验结果表明:Eu(III)在钛酸纳米管上的吸附在pH<6.0条件下受离子强度影响,而在pH>6.0条件下不受离子强度影响;腐殖酸HA/FA在低pH条件下可以促进Eu(III)在钛酸纳米管上的吸附,而在高pH条件下抑制Eu(III)在钛酸纳米管上的吸附.EXAFS微观分析结果表明:在pH<6.0条件下,吸附属于外层吸附机理;在pH>6.0条件下,吸附属于内层吸附机理.pH<6.0时,中心原子Eu周围只有Eu-O一个配位层,其平均键长为2.40,配位数在9左右;随着pH逐渐升高,第一配位层的配位数下降,表明吸附Eu原子配位的对称性下降.当吸附时间延长或pH升高,吸附原子Eu周围出现了Eu-Eu和Eu-Ti第二配位层,其平均键长分别为3.60和4.40,配位数分别在2或1左右,表明形成了内层吸附产物或表面沉淀或表面多聚体.腐殖酸HA/FA的存在,可以改变Eu(III)在钛酸纳米管表面的吸附形态和微观原子结构,Eu(III)不仅可以与钛酸纳米管的表面羟基直接键合形成二元表面复合物(Eu-TNTs),还可以通过HA/FA的桥连作用形成三元表面复合物(HA/FA-Eu-TNTs).这些研究结果对于评估放射性核素Eu(III)与纳米材料在分子水平上的作用机理及分析Eu(III)在环境中的物理化学行为具有重要的意义.     

Phosphate adsorption onto hematite: an in situ ATR-FTIR investigation of the effects of pH and loading level on the mode of phosphate surface complexation

Phosphate adsorption on hematite was characterized as a function of pH (3.5-8.9) and phosphate concentration (5-500 microM) by in situ ATR-FTIR spectroscopy. Under most conditions a mixture of different (inner-sphere) phosphate complexes existed at the hematite surface, with the relative importance of these complexes varying with pH and surface coverage. Experiments using D(2)O and H(2)O indicated the presence of two protonated phosphate surface complexes at pH/pD=3.5-7.0. Comparison to spectra of protonated aqueous phosphate species suggested that these surface complexes are monoprotonated. The difference in the IR spectra of these complexes is tentatively interpreted to result from a different surface coordination, with one surface complex coordinated in a monodentate binuclear (bridging) fashion, and the second as a monodentate mononuclear complex. Alternatively, the bridging complex may be a (protonated) monodentate mononuclear complex exhibiting strong hydrogen bonding to an adjacent surface site, and the second species a monodentate complex exhibiting limited hydrogen bonding. Formation of the bridging complex is favored at lower pH values and higher surface loadings in the 3.5-7.0 pH range. At the highest pH values studied (8.5-9.0) a third complex, interpreted to be a nonprotonated monodentate mononuclear complex, is present along with the monodentate monoprotonated surface species. The importance of the nonprotonated monodentate complex increases with increasing surface coverage at these high pH values.     

Adsorption of O-Phospho-L-Serine and L-Serine onto Poorly Crystalline Apatite

The adsorption of phosphoserine and serine was studied to determine the effect of amino acid functional groups on the surface reactivity of synthetic poorly crystalline apatite similar to bone mineral. The experimental results for phosphoserine and serine uptake agree respectively with the Langmuir and Freundlich models. Phosphoserine exhibits stronger adsorption capacity and a higher affinity constant for the surface crystals compared to serine molecules. The enhanced adsorption capacity noted for phosphoserine might be related to the presence of phosphate groups in the molecule, which are specific attachment sites. This observation suggests that the strength of phosphate bonds to the solid surface, especially to calcium ions, is higher than that of carboxyl and hydroxyl ones. Spectroscopic observations provide evidence of an adsorption mechanism involving the anionic species of the amino acids and the surface of the crystals. Thus, a change in the position of the band of carboxyl groups occurred for the adsorbed molecules compared to the native amino acids. This revealed that the molecular residues do interact with apatite surface calcium. The shift noted in the frequencies of the bands associated with carboxylate vibrations is more pronounced for phosphoserine, confirming the stronger interaction noted for this molecule. Based on these results, one can conclude that the sorbent and sorbate charged species play an important role in the mechanism of uptake of the amino acids onto crystal surfaces. This may contribute to a better understanding of the mechanism by which phosphoproteins could influence mineralization processes and caries. Copyright 2001 Academic Press.     

不同粒径的Ni/SiO2催化剂上CH4和CO2吸附活化的漫反射傅里叶变换红外光谱研究

 采用原位漫反射傅里叶变换红外光谱研究了CH4和CO2在不同粒径的Ni/SiO2催化剂上的吸附及活化. 结果表明,在不同粒径的催化剂上,检测到有CH4解离生成的CHx(x=1～3)物种,以及催化剂表面吸附的CHx物种与表面-OH 作用生成的CHx-O物种. CH4的裂解强烈依赖于催化剂表面Ni颗粒的大小,在粒径8 nm左右的Ni颗粒上, CH4较易解离; CO2难以直接在Ni/SiO2催化剂表面发生解离吸附,但CH4解离生成的吸附H对CO2的解离吸附具有明显的促进作用; CH4与CO2共吸附时,较小粒径的Ni可以促进CO2与表面氧物种发生反应,生成单齿表面碳酸盐物种.     

铂电极上吸附芳香分子的表面增强红外光谱研究

应用衰减全反射表面增强红外吸收光谱法分别研究了0.1 mol•L^－1 HClO₄中对硝基苯甲酸(PNBA)和0.1 mol•L^－1 KClO₄中吡啶(Py)在铂电极上的吸脱附. 结果表明在较高电位下(0.3～0.7 V vs. SCE) PNBA是通过其羧基脱质子后羧酸根的两个氧原子等位吸附在Pt电极表面, 而随着电位的负移, 除PNBA逐步脱附外, 还呈现出单个氧原子吸附的谱学特征. 光谱强度与电位的关系表明PNBA在铂电极表面吸脱附的中间电位约为0.2 V vs. SCE. 吡啶的吸附主要是通过氮原子的孤对电子及脱氢后的α碳原子与Pt电极表面键合. 在较宽的电位区间(0.4～－0.4 V vs. SCE)吡啶的吸附方式和取向基本维持不变.