Positive and negative TiO2 micropatterns on organic polymer substrates.
Positive and negative TiO2 micropatterns on organic polymer substrates.
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DOI：
10.1021/ja063716o
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发表时间：
2007-01
影响因子：
15
通讯作者：
Peng Yang;Min Yang;Shengli Zou;Jing-yi Xie;Wantai Yang
中科院分区：
文献类型：
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作者：
Peng Yang;Min Yang;Shengli Zou;Jing-yi Xie;Wantai Yang
有序二氧化钛（TiO2）薄膜因其在光催化、能量转换和光电技术方面的巨大潜力而受到越来越多的关注。这种薄膜通常被制成在诸如硅或各种聚合物等各种衬底上的涂层。二氧化钛薄膜的液相沉积（LPD）由于其非常温和的反应条件，在有机衬底上特别有前景。在本论文中，LPD是在润湿性图案的聚丙烯表面上进行的，以制造正负TiO2微图案。在两个双轴取向聚丙烯（BOPP）薄膜之间夹一层水溶液中的过硫酸铵，并采用光掩膜控制辐照区域。在较短的时间间隔内，可以在辐照区获得较高的亲水性，并且可以在辐照区和未辐照区之间形成有效的润湿性对比，从而进一步诱导形成两种类型的TiO2微图。到目前为止，大多数微图案的方法都是基于金（或其他贵金属）、硅和各种聚酯表面的自组装单层。然而，采用目前的方法，所使用的衬底类型不再有任何限制。我们的研究表明，锐钛矿型TiO2薄膜可以选择性地沉积在亲水区域，产生具有显著结合强度和良好线边缘敏锐度的正极图案，为各种惰性聚合物衬底的微加工提供了有效的解决方案。更令人惊讶的是，我们首次发现，通过简单地调整反应条件，TiO2也可以选择性地保留在疏水区域，形成负电荷模式。进一步的机理分析表明，与沉积条件无关，随着沉积时间的增加，TiO2的沉积模式逐渐发生变化，从最初的负向正转变。在沉积过程中，表面官能团发生了变化（从硫酸盐到羟基），由此产生的对TiO2亲和力的差异被用来解释这种从负到正的模式变化。这种负模式驳斥了传统观点，即只有亲水区域有利于形成TiO2薄膜，并可用于制造大面积（mm2）互连的TiO2微网络。传统的金属掩膜很难获得这样的网络，本方法有望为柔性掩膜和宏/介孔TiO2薄膜的制造提供新的策略。给出了一个示例，其中通过使用这种聚合物基光掩膜在BOPP表面上实现了聚丙烯酸的图案化光接枝。该方法的创新性源于其提供负模式的能力，而目前相关的方法只能从等效光掩膜中获得正模式。与复杂的光刻工艺不同，我们的辐照和制版工艺不需要使用正或负光刻胶，因此应该被证明是一种简单、快速和低成本的方法。
Ordered titanium dioxide (TiO2) films have received increasing attention because of their great potential in photocatalysis, energy conversion, and electrooptical techniques. Such films are often fabricated as coatings on various substrates such as silicon or a variety of polymers. Liquid-phase deposition (LPD) of TiO2 films is especially promising for organic substrates due to its very mild reaction conditions. In the present paper, LPD is conducted on a wettability-patterned polypropylene surface to fabricate positive and negative TiO2 micropatterns. A thin layer of ammonium persulfate in an aqueous solution was sandwiched between two biaxially oriented polypropylene (BOPP) films, and a photomask was employed to control the irradiation region. Within a short time interval, a high hydrophilicity could be obtained on the irradiation region, and an effective wettability contrast between the irradiated and unirradiated regions could be created to further induce the formation of two types of TiO2 micropatterns. Up until now, most approaches for micropatterning have been based on self-assembled monolayers on surfaces of gold (or other noble metals), silicon, and various polyesters. With the present method, however, there is no longer any limitation in the type of substrate used. Our work demonstrates that an anatase TiO2 film could be selectively deposited on a hydrophilic region, giving rise to a positive pattern with significant bonding strength and good line edge acuity, providing an effective solution toward the microfabrication on various inert polymer substrates. More surprisingly, we find, for the first time, that TiO2 could also be selectively retained on a hydrophobic region to form a negative pattern by simply adjusting the reaction conditions. Further analysis of the mechanism shows that, independent of the deposition conditions, the TiO2 deposition pattern changes gradually, from being initially negative to becoming positive as the deposition time increases. The surface functionality changes (from sulfate to hydroxyl groups) during the deposition, and the resulting difference in the affinity for TiO2 is used to interpret this negative-to-positive pattern change. Such negative patterns refute the conventional opinion that only hydrophilic regions favor the formation of TiO2 films and could be used to fabricate large areas (mm2) of interconnected TiO2 micronetworks. Such networks are difficult to obtain by conventional metallic masks, and the present method is expected to provide new strategies in the fabrication of flexible photomasks and macro/mesoporous TiO2 films. An example is given wherein a patterned photografting of poly(acrylic acid) on the surface of BOPP is achieved by using such a polymer-based photomask. The innovativeness of this method arises from its ability to provide negative patterning, whereas present related approaches have been found only to give positive patterns from an equivalent photomask. Unlike complex photolithography procedures, our irradiation and patterning process does not require the use of positive or negative photoresists, and should thus prove to be a simple, fast, and low-cost method.