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1.
Ur?ka L. ?tangar Urh ?ernigoj Polonca Treb?e Ksenija Maver Silvia Gross 《Monatshefte für Chemie / Chemical Monthly》2006,1(6):647-655
Transparent TiO2 films with a high photodegradation activity towards an azo dye in aqueous solution were prepared by sol–gel processing. Films
on soda–lime glass supports protected with a thin silica barrier layer exhibited better crystallization and monodisperse nanoparticles,
higher absorption of light below 370 nm, and higher photocatalytic activity than those films deposited on bare glass supports
proving the detrimental effect of interdiffused sodium ions on the development of the anatase nanostructure. The effect of
substrate was more pronounced in thinner films (300 nm) than in thicker ones (1200 nm), which were achieved by adding a template
(i.e. Pluronic F127) to the sol. 相似文献
2.
C. Perruchot M. M. Chehimi M. Delamar E. Cabet-Deliry B. Miksa S. Slomkowski M. A. Khan S. P. Armes 《Colloid and polymer science》2000,278(12):1139-1154
Thin chloride-doped polypyrrole films (PPyCl) were deposited chemically onto untreated and silane-treated planar glass plates
from aqueous solutions. The organosilanes used to treat the glass substrates were methyltriethoxysilane (Cl), propyltrimethoxysilane
(C3), octyltrimethoxysilane (C8) and aminopropyltriethoxysilane (APS). The decreasing order of hydrophobic character of silane-treated
glass slides, as measured by water contact angle measurements, was glass–APS ≅ glass–C8 > glass–C3 > glass–C1 > glass. X-ray
photoelectron spectroscopy was used to determine the surface chemical composition of the glass plates before and following
coating with the silane coupling agents and/or the PPy thin layer, respectively. The attenuation in intensity of the glass
Na1
s
peak enabled the average thickness of the various organosilane overlayers to be estimated. Atomic force microscopy showed
that the morphology of the organosilane overlayers was islandlike. The domains have a structure which depends upon the nature
of the organosilane in question. Scanning electron microscope images showed that the morphology of the PPyCl thin films was
homogeneous when coated onto glass–APS and glass–C8, but wrinkled at the surface of glass, glass–C1 and glass–C3 plates. Qualitative
peel tests using 3M adhesive tape showed very good adhesion of PPyCl to the glass–APS substrate, whereas adhesion was fairly
poor in the case of glass–PPy and PPy–alkylsilane–glass interfaces. The results of this multitechnique study suggest that
hydrophobic interactions are important to obtain homogeneous and continuous thin PPy films, but Lewis acid–base interactions
are the driving forces for strong and durable PPy–glass adhesion.
Received: 3 January 2000/Accepted: 19 May 2000 相似文献
3.
Ahmed M. El-Sayed Esmat M. A. Hamzawy 《Monatshefte für Chemie / Chemical Monthly》2006,137(9):1119-1125
Summary. The magnetic and microstructure properties of Fe2O3–0.4NiO–0.6ZnO–B2O3 glass system, which was subjected to heat treatment in order to induce a magnetic crystalline phase (Ni0.4Zn0.6-Fe2O4 crystals) within the glass matrix, were investigated. DSC measurement was performed to reveal the crystallization temperature
of the prepared glass sample. The obtained samples, produced by heat treatment at 765°C for various times (1, 1.5, 2, and
3 h), were characterized by X-ray diffraction, IR spectra, transmission electron microscopy, and vibrating sample magnetometer.
The results indicated the formation of spinel Ni–Zn ferrite in the glass matrix. Particles of the ferrite with sizes ranging
from 28 to 120 nm depending on the sintering time were observed. The coercivity values for different heat-treatment samples
were found to be in the range from 15.2 to 100 Oe. The combination of zinc content and sintering times leads to samples with
saturation magnetization ranging from 12.25 to 17.82 emu/g. 相似文献
4.
Angela Šurca Vuk Boris Orel Goran Dražič Philippe Colomban 《Monatshefte für Chemie / Chemical Monthly》2002,133(6):889-908
Summary. Orthovanadate (M
3+VO4; M = Fe, In) and vanadate (Fe2V4O13) thin films were prepared using sol-gel synthesis and dip coating deposition. Using analytical electron microscopy (AEM),
the chemical composition and the degree of crystallization of the phases present in the thin Fe–V–O films were investigated.
TEM samples were prepared in both orientations: parallel (plan view) and perpendicular (cross section) to the substrate. In
the first stages of crystallization, when the particle sizes were in the nanometer range, the classical identification of
phases using electron diffraction was not possible. Instead of measuring d values, experimentally selected area electron diffraction (SAED) patterns were compared to calculated (simulated) patterns
in order to determine the phase composition. The problems of evaluating the ratio of amorphous and crystalline phases in thin
films are reported.
Results of TEM and XRD as well as IR and Raman spectroscopy showed that the films made at lower temperatures (300°C) consisted of nanograins embedded in the dominating
amorphous phase. Characteristic vibrational spectra allowed to distinguish between the different crystalline phases, since
the IR and Raman bands showed broadening due to the decreasing particle size of the films thermally treated at lower temperatures. Vibrational
analysis also showed that the electrochemical cycling of crystalline films led to spectra that were in close agreement with
the spectra of the nanocrystalline films prepared at lower temperatures. The formation of a nanocrystalline structure is therefore
a prerequisite for obtaining a higher charging/discharging stability of Fe–V–O and In–V–O films.
Received October 4, 2001. Accepted (revised) November 23, 2001 相似文献
5.
Torsten Barfels Bernd Schmidt Andreas von Czarnowski Hans-Joachim Fitting 《Mikrochimica acta》2002,139(1-4):11-16
For investigation of the luminescent center profile cathodoluminescence measurements are used under variation of the primary
electron energy E
0 = 2…30 keV. Applying a constant incident power regime (E
0·I
0 = const), the depth profiles of luminescent centers are deduced from the range of the electron energy transfer profiles dE/dx.
Thermally grown SiO2 layers of thickness d = 500 nm have been implanted by Ge+-ions of energy 350 keV and doses (0.5–5)1016 ions/cm2. Thus Ge profiles with a concentration maximum of (0.4 – 4) at% at the depth of dm≅240 nm are expected. Afterwards the layers have been partially annealed up to T
a = 1100 °C for one hour in dry nitrogen. After thermal annealing, not only the typical violet luminescence (λ = 400 nm) of
the Ge centers is strongly increased but also the luminescent center profiles are shifted from about 250 nm to 170 nm depth
towards the surface. This process should be described by Ge diffusion processes, precipitation and finally Ge nanocluster
formation. Additionally, a Ge surface layer is piled-up extending to a depth of roughly 25 nm. 相似文献
6.
Conducting polypyrrole (PPy) and poly(pyrrole-2,6-dimethyl-β-cyclodextrin) [poly(Py-β-DMCD)] films were prepared by electrode
potential cycling on a gold electrode in aqueous and nonaqueous (acetonitrile) electrolyte solutions containing lithium perchlorate.
The resulting products were characterized with cyclic voltammetry, in situ UV–Vis spectroscopy, and in situ conductivity measurements.
For the electrosynthesis of poly(Py-β-DMCD), a (1:1) (mole–mole) (Py-β-DMCD) supramolecular cyclodextrin complex of pyrrole
previously characterized with proton NMR spectroscopy was used as starting material. A different cyclic voltammetric behavior
was observed for pyrrole and the poly(Py-β-DMCD) complex in aqueous and nonaqueous solutions during electrosynthesis. The
results show that in both solutions in the presence of cyclodextrin, the oxidation potential of pyrrole monomers increases.
However, the difference of oxidation potentials for films prepared in aqueous solution is larger than for the films prepared
in nonaqueous solution. In situ conductivity measurements of the films show that films prepared in acetonitrile solution are
more conductive than those synthesized in aqueous solutions. Maximum conductivity can be observed for PPy and poly(Py-β-DMCD)
films prepared in nonaqueous solution in the range of 0.10 < E
Ag/AgCl < 0.90 V and 0.30 < E
Ag/AgCl < 0.90 V, respectively. In situ UV–Vis spectroelectrochemical data for both films prepared potentiodynamically by cycling
the potentials from −0.40 < E
Ag/AgCl < 0.90 V in nonaqueous solutions are reported.
This paper is dedicated to Prof. Alan Bond on the occasion of his 65th birthday in recognition of his numerous contributions
toward electrochemistry. 相似文献
7.
Dhanaji S. Dalavi Meenatai J. Suryavanshi Sawanta S. Mali Dipali S. Patil Pramod S. Patil 《Journal of Solid State Electrochemistry》2012,16(1):253-263
In this paper, we report on the nickel oxide (NiO) thin films potentiostatically electrodeposited onto indium-doped tin oxide-coated
glass substrates by using two types of organic surfactants: (1) non-ionic: polyethylene glycol (PEG), polyvinylpyrrolidone
(PVP) and (2) anionic: sodium dodecyl sulfate (SDS). An aqueous solution containing nickel sulfate precursor and potassium
hydroxide buffer was used to grow the samples. The effect of organic surfactants on its structural, morphological, wettability,
optical, electrochromic, and in situ colorimetry were studied using X-ray diffraction, scanning electron microscopy, contact
angle, FT-IR spectroscopy, optical transmittance, cyclic voltammetry, and CIE system of colorimetry. X-ray diffraction patterns
show that the films are polycrystalline, consisting of NiO cubic phase. A nanoporous structure with pore diameter of about
150–200 nm was observed for pure NiO. The films deposited with the aid of organic surfactants exhibits various surface morphological
feature. PVP-mediated NiO thin film shows noodle-like morphology with well-defined surface area whereas, an ordered pore structure
composed of channels of uniform diameter of about 60–80 nm was observed for PEG. A compact and smooth surface with nanoporous
structure stem from SDS helps for improved electrochromic performance compared with that of NiO deposits from surfactant-free
solution. Wetting behavior shows, transformation from hydrophilic to superhydrophilic nature of NiO thin films deposited with
organic surfactant, which helps for much more paths for electrolyte access. The surfactant-mediated NiO produce high color/bleach
transmittance difference up to 57% at 630 nm. On oxidation of NiO/SDS, the CIELAB 1931 2° color space coordinates show the
transition from colorless to the deep brown state (L* = 84.41, a* = −0.33, b* = 4.41, and L* = 43.78, a* = 7.15, b* = 13.69), with steady decrease in relative luminance. The highest coloration efficiency of 54 cm2 C−1 with an excellent reversibility of 97% was observed for NiO/SDS thin films. 相似文献
8.
Silvia Gross Andrea Zattin Vito Di Noto Sandra Lavina 《Monatshefte für Chemie / Chemical Monthly》2006,137(5):583-593
Summary. Silica-based inorganic–organic hybrid thin films embedding the organically modified oxohafnium clusters (Hf4O2(OMc)12, OMc=OC(O)–C(CH3)=CH2) were obtained by photo-activated free radical copolymerisation of the methacrylate groups of the cluster with those of the
pre-hydrolysed (methacryloxypropyl)trimethoxysilane (MAPTMS, (CH2=C(CH3)C(O)O)(CH2)3Si(OCH3)3). By this route, a covalent anchoring of the cluster to the forming silica network was achieved. Samples characterized by
two different Si/Hf compositions (18:1, 5:1) were prepared. The surface and in-depth composition of the thin films were investigated
through Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). XPS depth profiles performed on the thin
layers evidenced a homogenous in depth distribution of the hafnium guest species within the whole silica films and sharp film-substrate
interfaces.
Broad band dielectric spectroscopy (BDS) measurements permitted to investigate the electric response of the obtained films
in the frequency and temperature range of 40 Hz – 1 MHz and 0–160°C. 相似文献
9.
Summary. Rhodococcus AJ270 is adsorbed by Dowex 1 at 15.4 mg dry weight per g resin with maximum amidase specific activity observed at lower
loadings. Bacteria form a monolayer on the resin surface, and adsorption is complete within 2 min. AJ270 can be entrapped
in agar and agarose gels (optimum loading: 20 mg dry weight bacteria per cm3 gel). Adsorption and entrapment improve amidase thermal stability 3–4 fold, and entrapment shifts the pH optimum from 8 to 7. Adsorbed and free bacteria show similar values for K
m and V
max, but entrapped bacteria have higher K
m values. Compared with bacteria adsorbed to Dowex, the activity per cm3 of matrix of agar-entrapped AJ270 is eight-fold higher. In stirred-tank reactors, exposure to acrylic acid reduces the amidase
activity of the biocatalyst in the hydrolysis of acrylamide. In column reactors, entrapped AJ270 suffers little reduction
in amidase activity against 0.25 M acrylamide over 22 h continuous operation.
Received November 18, 1999. Accepted December 14, 1999 相似文献
10.
Proton conducting tantalum oxide films were deposited on ITO (Indium Tin Oxide) coated glass, fused silica and soda-lime glass
substrates by spin coating using a sol-gel process. The coating solutions were prepared using Ta(OC2H5)5 as a precursor. X-ray diffraction studies determined that the sol-gel films, heat treated at temperatures below 400°C, were
amorphous. Films heat treated at higher temperatures were crystalline with the hexagonal δ-Ta2O5 structure. The solar transmission values (T
s
) of tantala films on glass generally range from 0.8–0.9, depending on thickness. The refractive index and the extinction
coefficient were evaluated from transmittance characteristics in the UV-VIS-NIR regions. The refractive index values calculated
at λ=550 nm increased fromn=1.78 to 1.97 with increasing heat treatment from 150 to 450°C. The films heat treated at different temperatures showed low
absorption, with extinction coefficients of smaller thank=1×10−3 in the visible range. Impedance spectroscopic investigations performed on Ta2O5 films revealed that these films have a protonic conductivity of 3.2×10−4S/m. The films are suitable for proton conducting layers in electrochromic (EC) devices. 相似文献
11.
Olaf Baake Peter S. Hoffmann Andreas Klein Beatrix Pollakowski Burkhard Beckhoff Marina L. Kosinova Nadeshda I. Fainer Veronica S. Sulyaeva Valentina A. Trunova Wolfgang Ensinger 《Analytical and bioanalytical chemistry》2009,395(6):1901-1909
Films of BC
x
N
y
were produced in a plasma-enhanced chemical vapor deposition process using trimethylborazine as precursor and with H2, He, N2, and NH3, respectively, as auxiliary gas. These films deposited on Si(100) wafers or fused quartz glass substrates were characterized
chemically by X-ray photoelectron spectroscopy and by synchrotron radiation-based total-reflection X-ray fluorescence combined
with near-edge X-ray absorption fine structure. Independent of the auxiliary gas, the B–N bonds are dominating. Furthermore,
B–C and N–C bonds were identified. Oxygen, present in the bulk (in contrast to the surface layer of some nanometers, where
molecular oxygen and/or water are absorbed) as an impurity, is bonded to boron or to carbon, respectively. The relation of
boron and nitrogen changes with the character of the auxiliary gas: c
B/c
N ≈ 4:3 (for H2 and He) and c
B/c
N ≈ 1 (for N2 or NH3). Furthermore, physical properties such as the refractive index and the optical band-gap energy were determined. 相似文献
12.
Ahmed M. El-Sayed Esmat M. A. Hamzawy 《Monatshefte für Chemie / Chemical Monthly》2006,1(3):1119-1125
The magnetic and microstructure properties of Fe2O3–0.4NiO–0.6ZnO–B2O3 glass system, which was subjected to heat treatment in order to induce a magnetic crystalline phase (Ni0.4Zn0.6-Fe2O4 crystals) within the glass matrix, were investigated. DSC measurement was performed to reveal the crystallization temperature
of the prepared glass sample. The obtained samples, produced by heat treatment at 765°C for various times (1, 1.5, 2, and
3 h), were characterized by X-ray diffraction, IR spectra, transmission electron microscopy, and vibrating sample magnetometer.
The results indicated the formation of spinel Ni–Zn ferrite in the glass matrix. Particles of the ferrite with sizes ranging
from 28 to 120 nm depending on the sintering time were observed. The coercivity values for different heat-treatment samples
were found to be in the range from 15.2 to 100 Oe. The combination of zinc content and sintering times leads to samples with
saturation magnetization ranging from 12.25 to 17.82 emu/g. 相似文献
13.
Graham A. Bowmaker Paul A. Kilmartin Graham A. Wright 《Journal of Solid State Electrochemistry》1999,3(3):163-171
Stable, yellow anodic films of parathiocyanogen (SCN)
x
were formed on a platinum electrode from 2.8 M KSCN in methanol at 45 °C at a constant current of 20–40 mA cm−2 for 15–30 min. Loosely bound orange crystals of a more amorphous character were removed by rinsing to leave an adherent yellow
film with sharp Raman bands under 647.1 nm laser excitation at 627 cm−1 (vCS), 1152 cm−1 and 1236–1261 cm−1 (vNN and vCN). The lack of electroactivity and short-lived photocurrents pointed to an insulating film at potentials up to 1.0 V (SHE).
At more positive potentials, longer-lasting photocurrents were obtained, consistent with breakdown of the insulating film.
XPS scans confirmed N:C:S ratios close to 1:1:1, with a deficiency of S of some 10% due to S lost as sulfate at the film surface.
Oxidation of SeCN− in neutral aqueous solution led to the formation of a less-stable orange paraselenocyanogen film with a Raman band at 1256–1267 cm−1, which decomposed within a day to grey selenium.
Received: 12 December 1997 / Accepted: 23 March 1998 相似文献
14.
Yan Sun Masanori Koshimizu Shunji Kishimoto Keisuke Asai 《Journal of Sol-Gel Science and Technology》2012,62(3):313-318
Transparent and crack-free Pr-doped silica glass scintillators were successfully synthesized using the sol–gel method. A peak
found at 301 nm in the photoluminescence spectrum was ascribed to a radiative transition of the Pr3+ emission center. The associated excitation peak was located at 276 nm. The energy of the excitation peak (4.50 eV) was significantly
lower than the energy gap (5.83 eV) of the 1S0 to 3H4
f–f transition. Therefore, the f–f transition was excluded as the origin, and the transition was attributed to 5d–4f. In the absorption spectrum, several bands of the f–f transition were observed. Fourier transform infrared spectroscopy was employed to understand the microstructural features
and OH group concentration in the Pr3+-doped silica glass. It was revealed that a Si–O network had been successfully formed, and that the OH group concentration
decreased with increasing thermal treatment temperature reaching a saturation value for temperatures higher than 750 °C. The
absence of praseodymium oxide nanocrystalline clusters was confirmed by transmission electron microscopy (TEM), even in the
sample with the highest Pr ion concentration. Scintillation properties of the Pr3+-doped silica glass were also characterized. The scintillation decay time constants were estimated to be approximately 1.3
and 14 ns, which supports the assignment of the luminescence to the 5d–4f transition. The scintillation light yield of the Pr3+-doped silica glass was estimated to be approximately 130 photons/MeV. 相似文献
15.
Core–shell latex particles made of a poly(butyl methacrylate) (PBMA) core and a thin polypyrrole (PPy) shell were synthesized
by two-stage polymerization. In the first stage, PBMA latex particles were synthesized in a semicontinuous process by free-radical
polymerization. PBMA latex particles were labeled either with an energy donor or with an energy acceptor, in two different
syntheses. These particles were used in a second stage as seeds for the synthesis of the core–shell particles. The PPy shell
was polymerized around the PBMA core latex in an oxidative chemical in situ polymerization. Proofs for the success of the
core–shell synthesis were obtained using nonradiative energy transfer (NRET) and atomic force microscopy (AFM). NRET gives
access to the rate of polymer chain migration between adjacent particles in a film annealed at a temperature above the glass-transition
temperature T
g of the particles. Slower chain migration of the PBMA polymer chains was obtained with the PBMA–PPy core–shell particles compared
to rate of the PBMA polymer chain migration found with the pure, uncoated PBMA particles. This result is due to the coating
of PBMA by PPy, which hinders the migration of the PBMA polymer chains between adjacent particles in the film. This observation
has been confirmed by AFM measurements showing that the flattening of the latex film surface is much slower for the core–shell
particles than for the pure PBMA particles. This result can again be explained by the presence of a rigid PPy shell around
the PBMA core. Thus, these two complementary methods have given evidence that real core–shell particles were synthesized and
that the shell seriously hinders film formation of the particles in spite of the fact that it is very thin (thickness close
to 1 nm) compared to the size (750 and 780 nm in diameter) of the PBMA core. Transparency measurements confirm the results
obtained by NRET and AFM. When the films are placed at a temperature higher than the T
g of PBMA, the increase in transparency is faster for films made with the uncoated PBMA particles than for films made with
the coated PBMA particles. This result indicates again that the presence of the rigid PPy layer around the PBMA core reduces
considerably the speed at which the structure of the film is modified when heated above the T
g of PBMA.
Received: 02 September 1999 Accepted: 21 December 1999 相似文献
16.
Valdek Mikli 《Mikrochimica acta》2006,155(1-2):205-208
The study covers a problem frequently encountered in the quantification of the results of wavelength-dispersive spectrometry
(WDS) for the composition analysis of thin films. The characteristics of a Parallel Beam Spectrometer and traditional WDS
systems were examined and olivine mineral – (Mg, Fe)2SiO4 (O – 44.03 wt%, Mg – 31.1 wt%, Si – 19.56 wt%, Fe – 5.06 wt%, Ni – 0.16 wt%, Mn – 0.09 wt%) was used as a reference material.
Low accelerating voltage at 7 kV and beam current 400 nA were applied. Both methods yielded 30–35% of Mn. This is attributed
to the overlapping of the MnLα first-order and the MgKα second-order lines. Studies of the influences of the second- and the
third-order lines show that the second-order lines from Kα and Lα X-ray counts affected significantly the obtained WDS spectra
when the influence of Mα counts was insignificant. Furthermore, the third-order lines did not have a marked effect on the
analysis results. 相似文献
17.
In weakly acidic buffer medium, vitamin B1 (VB1) interacts with gold nanoparticles to form a binding product, which resulted in a significant enhancement of resonance Rayleigh
scattering (RRS) intensity and the appearance of a new RRS spectrum. The maximum RRS peak was at 368 nm, and there are three
smaller scattering peaks that were at 284 nm, 440 nm and 495 nm, respectively. The enhanced RRS intensity (ΔI) was directly proportional to the concentration of VB1 in the range of 0–2.8 × 10−7 mol L−1. The method had high sensitivity and its detection limit (3σ) was 0.9 ng mL−1. The optimum conditions and the influencing factors have been investigated. The method had good selectivity, which could
be observed from the influence of coexisting substances. A sensitive, simple and fast RRS method for the determination of
VB1 with gold nanoparticle probe has been developed. In addition, the reasons for RRS enhancement were discussed. 相似文献
18.
19.
Abdul-Majeed WS Parada JH Zimmerman WB 《Analytical and bioanalytical chemistry》2011,401(9):2713-2722
In this work, an optimization study was conducted to investigate the performance of a custom-designed miniaturized dielectric
barrier discharge (DBD) microplasma chip to be utilized as a radiation source for mercury determination in water samples.
The experimental work was implemented by using experimental design, and the results were assessed by applying statistical
techniques. The proposed DBD chip was designed and fabricated in a simple way by using a few microscope glass slides aligned
together and held by a Perspex chip holder, which proved useful for miniaturization purposes. Argon gas at 75–180 mL/min was
used in the experiments as a discharge gas, while AC power in the range 75–175 W at 38 kHz was supplied to the load from a
custom-made power source. A UV-visible spectrometer was used, and the spectroscopic parameters were optimized thoroughly and
applied in the later analysis. Plasma characteristics were determined theoretically by analysing the recorded spectroscopic
data. The estimated electron temperature (T
e = 0.849 eV) was found to be higher than the excitation temperature (T
exc = 0.55 eV) and the rotational temperature (T
rot
= 0.064 eV), which indicates non-thermal plasma is generated in the proposed chip. Mercury cold vapour generation experiments
were conducted according to experimental plan by examining four parameters (HCl and SnCl2 concentrations, argon flow rate, and the applied power) and considering the recorded intensity for the mercury line (253.65 nm)
as the objective function. Furthermore, an optimization technique and statistical approaches were applied to investigate the
individual and interaction effects of the tested parameters on the system performance. The calculated analytical figures of
merit (LOD = 2.8 μg/L and RSD = 3.5%) indicates a reasonable precision system to be adopted as a basis for a miniaturized
portable device for mercury detection in water samples. 相似文献
20.
Comparison between Different Hydrolysis Processes of Vine-Trimming Waste to Obtain Hemicellulosic Sugars for Further Lactic Acid Conversion 总被引:1,自引:0,他引:1
Moldes AB Bustos G Torrado A Domínguez JM 《Applied biochemistry and biotechnology》2007,143(3):244-256
Trimming vine shoot samples were treated with water under selected operational conditions (autohydrolysis reaction) to obtain
a liquid phase containing hemicellulose-decomposition products. In a further acid-catalyzed step (posthydrolysis reaction),
xylooligosaccharides were converted into single sugars for the biotechnological production of lactic acid using Lactobacillus
pentosus. A wide range of temperatures, reaction times, and acid concentrations were tested during the autohydrolysis–posthydrolysis
process to investigate their influence on hemicellulose solubilization and reaction products. The maximum concentration of
hemicellulosic sugars was achieved using autohydrolysis at 210 °C followed by posthydrolysis with 1% H2SO4 during 2 h. Data from autohydrolysis–posthydrolysis were compared with the results obtained at the optima conditions assayed
for prehydrolysis (3% H2SO4 at 130 °C during 15 min) based on previous works. Prehydrolysis extracted more hemicellulosic sugars from trimming vine shoots;
however, the protein content in the hydrolysates from autohydrolysis–posthydrolysis was higher. The harsher conditions assayed
during the autohydrolysis process and the higher content of protein after this treatment could induce Maillard reactions decreasing
consequently the concentration of hemicellulosic sugars in the hydrolysates. Therefore, despite the several advantages of
autohydrolysis (less equipment caused by the absence of mineral acid, less generation of neutralized sludges, and low cost
of reagents) the poor results obtained in this work with no detoxified hydrolysates (Q
P = 0.36 g/L h, Q
S = 0.79 g/L h, Y
P/S = 0.45 g/g, Y
P/Sth = 61.5 %) or charcoal-treated hydrolysates (Q
P = 0.76 g/L h, Q
S = 1.47 g/L h, Y
P/S = 0.52 g/g, Y
P/Sth = 71.5 %) suggest that prehydrolysis of trimming vine shoots with diluted H2SO4 is more attractive than autohydrolysis-posthydrolysis for obtaining lactic acid through fermentation of hemicellulosic sugars
with L. pentosus. Besides the higher hemicellulosic sugars concentration achieved when using the prehydrolysis technology, no detoxification
steps are required to produce efficiently lactic acid (Q
P = 1.14 g/L h; Q
S = 1.64 g/L h; Y
P/S = 0.70 g/g; Y
P/Sth = 92.6 %), even when vinification lees are used as nutrients (Q
P = 0.89 g/L h; Q
S = 1.54 g/L h; Y
P/S = 0.58 g/g; Y
P/Sth = 76.1 %). 相似文献